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1.
Bioresour Technol ; 344(Pt A): 126161, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34678453

ABSTRACT

Using waste biomass to prepare various products by environmentally benign processes is a good way to practice green and sustainable development. In this paper, high porosity and surface area biomass activated carbon was obtained by pyrolysis of pine sawdust without using any chemicals after steam bursting pretreatment. Under hydrothermal conditions at 160 ℃, the differences of steam bursting at 300, 500, or 700 psi pressures on the structure and surface chemical groups of the final activated carbons product were compared. The characterization showed that the specific surface areas and micropore volumes decreased with the increase of pressure, while the relative content of oxygen-containing functional groups changed slightly. The sample obtained following 300 psi pretreatment (HPB300) offered the highest BET surface area and pore volume, 962 m2/g and 0.526 cm3/g respectively, and which also achieved the highest adsorption amounts for both methylene blue (MB) and perfluorooctanoic acid (PFOA).


Subject(s)
Charcoal , Methylene Blue , Adsorption , Biomass , Caprylates , Fluorocarbons , Porosity , Steam
2.
J Environ Sci (China) ; 98: 94-102, 2020 Dec.
Article in English | MEDLINE | ID: mdl-33097163

ABSTRACT

When wood-based activated carbon was tailored with quaternary ammonium/epoxide (QAE) forming compounds (QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid (PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before half-breakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.


Subject(s)
Caprylates , Charcoal , Adsorption , Epoxy Compounds , Fluorocarbons
3.
J Environ Radioact ; 220-221: 106300, 2020 Sep.
Article in English | MEDLINE | ID: mdl-32560888

ABSTRACT

Concentrations of naturally occurring radioactive material (NORM) in Marcellus Shale produced water presents a challenge for effective management and treatment, because of the vast fluid volumes generated. With an increased emphasis on beneficial reuse and resource recovery from the produced waters, a rapid, yet reliable, method for quantifying radium in these produced waters is needed. The high total dissolved solids (TDS) concentration introduces difficulties when measuring 226Ra by recommended EPA methods that were specifically developed several decades ago for drinking water. While other techniques for measuring radium in these high-TDS fluids have since been developed, these newer techniques often require extensive and complicated pre-concentration steps; and they thus require extensive analytical chemistry skills, utilize hazardous chemicals like hydrofluoric acid, demand long holding times or measurement times, and require high sample volumes. We present a rapid method for 226Ra measurements in high-TDS produced waters by liquid scintillation counting, which has been corroborated herein by concurrent gamma spectrometry analyses. Samples were prepared for analysis by evaporating the fluid and re-suspending the evaporate with acidified distilled deionized water prior to liquid scintillation counting for 1 h. This protocol yielded radium recoveries ≥93%. Per this protocol, the alpha and beta spectra of 226Ra and its daughters were computationally separated by alpha-beta discrimination and spectrum deconvolution. The minimum detectable activities of 226Ra was 0.33 Bq/L (9.0 pCi/L) when the counting time was 60 min and the sample volume was 4 mL. Nine produced waters of varying TDS and radium concentrations from the Marcellus Shale Formation were analyzed by this method and compared with gamma spectroscopy; and these yielded comparable results with an R2 of 0.92. The reduced sample preparation steps, low cost, and rapid analysis position this as a well-suited protocol for field-appraisal and screening, when compared to comprehensive radiochemical analysis. We offer that for a given produced water region, routine and local liquid scintillation analyses can be compared and calibrated with infrequent gamma spec analyses, so as to yield a near-real time protocol for monitoring 226Ra levels during hydrofracturing operations. We present this as a pragmatic and efficient protocol for monitoring 226Ra when produced water samples host low levels of 228Ra-since the progeny of 228Ra can significantly confound the LSC analyses.


Subject(s)
Radiation Monitoring , Scintillation Counting , Hydraulic Fracking , Radium , Water Pollutants, Radioactive
4.
Chemosphere ; 242: 125233, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31896207

ABSTRACT

Acid/base/oxidant pretreatment influenced subsequent quaternary ammonium epoxide compounds modified carbon (QAE-AC) and hence PFOA and nitrate removal. This work discerned that the most favorable QAE-AC protocol for PFOA removal was achieved when the wood carbon pretreated with HNO3 to adjust the carbon's slurry pH to 4.77, and tailored with the QUAB188. For nitrate removal, the most favorable when the carbon was pretreated with NaOH to raise the carbon's slurry pH to 9.34, and then loaded with the QUAB360. Based on experimentally results and molecular model, we found that pore volume, phenolic groups and the surface charge were the main factors affecting the PFOA removal, while the only factor affecting nitrate removal was surface charge. The QUAB's epoxide functionalities have cross-linked with phenolics along the activated carbon's graphene edge sites. QAE is preferentially reacted with the phenolic in the micropores and mesopores of carbon, and some QAE molecules form new "pore-like structures" outside the pores with the graphene planes or other QAE molecules. This pore-like structure hosted adsorption capacity by the quaternary ammonium. The favorable PFOA adsorption sites were in smaller mesopores via both hydrophobic interaction and electrostatic interaction; and nitrate sorption was occurring in the smaller micropores via anion exchange. Therefore, it can be considered that QAE-AC can simultaneously adsorb PFOA and nitrate in water.


Subject(s)
Caprylates/chemistry , Fluorocarbons/chemistry , Models, Chemical , Nitrates/chemistry , Quaternary Ammonium Compounds/chemistry , Water Pollutants, Chemical/chemistry , Adsorption , Ammonium Compounds/chemistry , Anions , Charcoal/chemistry , Epoxy Compounds , Oxidants , Water
5.
J Environ Radioact ; 211: 106070, 2020 Jan.
Article in English | MEDLINE | ID: mdl-31585380

ABSTRACT

Beneficial reuse and resource recovery of produced water often require treatment to remove radium before valuable products are extracted. The radium content of the treatment waste solids and beneficial products must be accurately determined when evaluating the efficacy and social validity of such treatments. While gamma spectroscopy remains the recommended method for radium measurements, these measurements can be impacted by the composition/mineralogy of the solids, which influence the attenuation of the gamma decay energy - with denser sediments incurring greater degrees of attenuation. This self-attenuation must be accounted for when accurately measuring radium, otherwise radium measurements are found to be inaccurate, sometimes by as much as 50%. To meet industry needs, measurements should be both accurate and rapid, even for small sample sizes. Consequently, we propose a rapid method for accurate radium measurements with an empirical technique to account for sample attenuation in well-detector gamma spectroscopy. This technique utilizes the sample density and sample volume in the measuring vial. These corrections are relevant to a wide range of solid samples and sediment densities that may be encountered during treatment and management of oil and gas solids, including clays, environmental sediment samples, sand grains, and precipitated salts. These corrections can also be applied for situations were low volumes of material are present, as in bench scale studies, thereby rendering this technique applicable to a wider range of scenarios.


Subject(s)
Radium/analysis , Gamma Rays , Radiation Monitoring , Spectrum Analysis , Wastewater
6.
Environ Sci Technol ; 53(17): 10295-10302, 2019 Sep 03.
Article in English | MEDLINE | ID: mdl-31429285

ABSTRACT

Radium measurements in high total dissolved solids (TDS) fluids from oil and gas extraction can have unfavorable precision and accuracy, in part because these high-level impurities incur attenuation. γ spectroscopy is often recommended for determining radium activities in these fluids, but even this method can produce a range of reported activities for the same sample. To reduce measurement duration and to maintain or improve accuracy, we propose a method to rapidly assess both 226Ra and 228Ra and to account for the self-attenuation of γ rays in high-TDS oil and gas fluids when they are monitored by a well detector. In this work, comparisons between a NaCl-only and a multi-cation-chloride synthetic brine spiked with known amounts of 226Ra and 228Ra indicated that both the TDS concentration and the type of TDS (i.e., Na only vs Na-Mg-Ba-Ca-Sr) influenced self-attenuation in well-detector γ spectroscopy, thus highlighting the need to correct for this TDS-influenced self-attenuation. Radium activities can be underestimated if the correction is not applied. For instance, 226Ra activities could be ∼40% lower in a sample when measured directly at the 186 keV energy level if the attenuation of the high TDS of the fluid is not considered. We also showed that using a NaCl-only brine to match the matrix of high-TDS oil and gas brines is inadequate to produce accurate measurements, rather, the full set of cations should be included.


Subject(s)
Radium , Water Pollutants, Radioactive , Gamma Rays , Spectrum Analysis , Water
7.
J Environ Manage ; 234: 21-27, 2019 Mar 15.
Article in English | MEDLINE | ID: mdl-30599326

ABSTRACT

The authors tailored coconut-based activated carbons with a quaternary ammonium epoxide (QAE) surfactant that greatly increased the carbon's capacity for sorbing nitrate from water. This QAE-tailored carbon processed deionized water spiked with 50 mg/L NO3- through rapid small scale column tests; and achieved half-breakthrough at 477 bed volumes. This favorably compared to 52 bed volumes for the pristine coconut activated carbon. The QAE employed herein was QUAB 360. Most favorable pretreatment of the carbon was achieved via NaOH immersion, which created extensive phenolic functionality on the carbon's graphene edges, and raised the carbon's slurry pH to 9.3-9.6. These phenolics served as the anchor for the QUAB's epoxide reactions. This pretreatment offered the highest QUAB loading onto the carbon, which in turn netted the most nitrate removal. Per X-ray photoelectron spectroscopy, favorable QUAB360 preloading incurred a 1.62% increase in the quaternary N content of these activated carbons. The phenolic functionality that followed pretreatment was discerned by Boehm titrations; and these mathematically matched with Gaussian-based models that were fitted to incremental titration data. The most favorable QUAB-loaded variants were the ones whose pretreated precursors had exhibited the highest peak of functionality in the 9.3-10.4 pH range-corresponding to the pKa of phenolics. If the precursor pH was below the 9.3-9.6 range-as induced by acids or H2O2, then the QUAB's epoxide intermediate apparently over-reacted with the hydroxylated functionality of other QUAB molecules, rather than with phenolic functionality of the carbon's graphene edge sites.


Subject(s)
Charcoal , Cocos , Adsorption , Epoxy Compounds , Hydrogen Peroxide
8.
Sci Total Environ ; 660: 577-585, 2019 Apr 10.
Article in English | MEDLINE | ID: mdl-30641385

ABSTRACT

This research reports an integrated method for synthesizing a quaternary nitrogen-grafted activated carbon that is derived from a subbituminous coal source. The protocol employed nitric acid oxidation, thermal ammonia treatment and methyl iodide quaternization. The quaternized product greatly increased trifluoroacetate (TFA, CF3COO-) removal from a groundwater source. This quaternary nitrogen-grafted carbon (designated AWNQ) exhibited the highest TFA adsorption capacity of 32.9 mg/g and exhibited high energy of adsorption for TFA. Also, when processing groundwater that had been spiked with 200 ppb TFA, this quaternary nitrogen-grafted carbon removed TFA to 3 ppb breakthrough for 1860 BV, which was twelve times longer than the 150 BV for the pristine carbon. The enhanced sorption was attributed to its high quaternary nitrogen ratio (1.30, at.%), which offered 0.69 meq/g positive charge. Furthermore, high regeneration efficiency (89.5%) was achieved by the proposed regeneration protocol. The mixed regenerant (ethanol and NaCl solution) effectively stripped off the loaded TFA and regenerated the quaternary nitrogen sites. This quaternary nitrogen-grafted carbon with its fast and high uptake capacity offered technical promise for TFA removal from groundwater.

9.
Environ Sci Process Impacts ; 21(2): 308-323, 2019 Feb 21.
Article in English | MEDLINE | ID: mdl-30382267

ABSTRACT

Unconventional oil and gas residual solid wastes are generally disposed in municipal waste landfills (RCRA Subtitle D), but they contain valuable raw materials such as proppant sands. A novel process for recovering raw materials from hydraulic fracturing residual waste is presented. Specifically, a novel hydroacoustic cavitation system, combined with physical separation devices, can create a distinct stream of highly concentrated sand, and another distinct stream of clay from the residual solid waste by the dispersive energy of cavitation conjoined with ultrasonics, ozone and hydrogen peroxide. This combination cleaned the sand grains, by removing previously aggregated clays and residues from the sand surfaces. When these unit operations were followed by a hydrocyclone and spiral, the solids could be separated by particle size, yielding primarily cleaned sand in one flow stream; clays and fine particles in another; and silts in yet a third stream. Consequently, the separation of particle sizes also affected radium distribution - the sand grains had low radium activities, as lows as 0.207 Bq g-1 (5.6 pCi g-1). In contrast, the clays had elevated radium activities, as high as 1.85-3.7 Bq g-1 (50-100 pCi g-1) - and much of this radium was affiliated with organics and salts that could be separated from the clays. We propose that the reclaimed sand could be reused as hydraulic fracturing proppant. The separation of sand from silt and clay could reduce the volume and radium masses of wastes that are disposed in landfills. This could represent a significant savings to facilities handling oil and gas waste, as much as $100 000-300 000 per year. Disposing the radium-enriched salts and organics downhole will mitigate radium release to the surface. Additionally, the reclaimed sand could have market value, and this could represent as much as a third of the cost savings. Tests that employed the toxicity characteristic leaching protocol (TCLP) on these separated solids streams determined that this novel treatment diminished the risk of radium mobility for the reclaimed sand, clays or disposed material, rendering them better suited for landfilling.


Subject(s)
Hydraulic Fracking , Radioactive Waste , Refuse Disposal/methods , Acoustics , Metals/analysis , Particle Size , Radium/analysis , Solid Waste/analysis , Waste Disposal Facilities
10.
Water Sci Technol ; 78(7): 1489-1498, 2018 Nov.
Article in English | MEDLINE | ID: mdl-30427789

ABSTRACT

The authors used a nitric acid (HNO3)-sodium dodecyl benzene sulfonate (SDBS) method to modify a lignite-based activated carbon. These modified carbons were appraised for their removal of Cd(II) from aqueous solutions. Response surface methodology was employed to optimize the preparation factors including nitric acid concentration CN, temperature T and SDBS concentration CS. Statistical analysis indicated that the interaction of CN and CS incurred the most effect on the maximum cadmium adsorption capacity (Qm). The optimal Qm appeared at CN = 3.29 mol/L, T = 76 °C and CS=30,700 mg/L. The optimal protocol achieved 44.21 mg/g Qm for Cd(II) which was about 7 times larger than for this pristine lignite activated carbon (LAC) (6.78 mg/g). The physical-chemical properties of the modified activated carbons following each synthesis step were characterized relative to their surface area, oxygen functionality, and external surface charge. It was confirmed that the developed surface area, functional groups and negative charges were mainly responsible for the higher adsorption capacity for the LAC that have been more favorably tailored by this HNO3-SDBS protocol.


Subject(s)
Cadmium/analysis , Nitric Acid/chemistry , Waste Disposal, Fluid/methods , Water Pollutants, Chemical/analysis , Adsorption , Carbon , Hydrogen-Ion Concentration , Surface-Active Agents/chemistry , Wastewater
11.
Chemosphere ; 201: 756-763, 2018 Jun.
Article in English | MEDLINE | ID: mdl-29550569

ABSTRACT

In order to obtain a high adsorption capacity for perchlorate, the epoxide-forming quaternary ammonium (EQA) compounds were chemically bonded onto granular activated carbon (GAC) surface by cationic reaction. The optimum preparation condition of the cationic GAC was achieved while applying softwood-based Gran C as the parent GAC, dosing EQA first at a pH of 12, preparation time of 48 h, preparation temperature of 50 °C, and mole ratio of EQA/oxygen groups of 2.5. The most favorable cationic GAC that had the QUAB360 pre-anchored exhibited the highest perchlorate adsorption capacity of 24.7 mg/g, and presented the longest bed volumes (3000 BV) to 2 ppb breakthrough during rapid small scale column tests (RSSCTs), which was 150 times higher than that for the pristine Gran C. This was attributed to its higher nitrogen amount (1.53 At%) and higher positive surface charge (0.036 mmol/g) at pH 7.5. Also, there was no leaching of the quaternary ammonium detected in the effluent of the RSSCTs, indicating there was no secondary pollution occurring during the perchlorate removal process. Overall, this study provides an effective and environmental-friendly technology for improving GAC perchlorate adsorption capacity for groundwater treatment.


Subject(s)
Charcoal/chemistry , Groundwater/chemistry , Perchlorates/analysis , Water Pollutants, Chemical/analysis , Water Purification/methods , Adsorption , Cations , Epoxy Compounds/chemistry , Quaternary Ammonium Compounds/chemistry , Surface Properties
12.
Chemosphere ; 184: 429-437, 2017 Oct.
Article in English | MEDLINE | ID: mdl-28618275

ABSTRACT

Polypyrrole modified activated carbon was used to remove sulfate from acid mine drainage water. The polypyrrole modified activated carbon created positively charged functionality that offered elevated sorption capacity for sulfate. The effects of the activated carbon type, approach of polymerization, preparation temperature, solvent, and concentration of oxidant solution over the sulfate adsorption capacity were studied at an array of initial sulfate concentrations. A hardwood based activated carbon was the more favorable activated carbon template, and this offered better sulfate removal than when using bituminous based activated carbon or oak wood activated carbon as the template. The hardwood-based activated carbon modified with polypyrrole removed 44.7 mg/g sulfate, and this was five times higher than for the pristine hardwood-based activated carbon. Various protocols for depositing the polypyrrole onto the activated carbon were investigated. When ferric chloride was used as an oxidant, the deposition protocol that achieved the most N+ atomic percent (3.35%) while also maintaining the least oxygen atomic percent (6.22%) offered the most favorable sulfate removal. For the rapid small scale column tests, when processing the AMD water, hardwood-based activated carbon modified with poly pyrrole exhibited 33 bed volume compared to the 5 bed volume of pristine activated carbons.


Subject(s)
Charcoal/chemistry , Polymers/chemistry , Pyrroles/chemistry , Sulfates/isolation & purification , Adsorption , Mining , Water Pollutants, Chemical/isolation & purification , Wood
13.
Water Res ; 103: 233-244, 2016 10 15.
Article in English | MEDLINE | ID: mdl-27470293

ABSTRACT

Hypersaline hydrofracturing brines host very high salt concentrations, as high as 120,000-330,000 mg/L total dissolved solids (TDS), corresponding to ionic strengths of 2.1-5.7 mol/kg. This is 4-10 times higher than for ocean water. At such high ionic strengths, the conventional equations for computing activity coefficients no longer apply; and the complex ion-interactive Pitzer model must be invoked. The authors herein have used the Pitzer-based PHREEQC computer program to compute the appropriate activity coefficients when forming such precipitates as BaSO4, CaSO4, MgSO4, SrSO4, CaCO3, SrCO3, and BaCO3 in hydrofracturing waters. The divalent cation activity coefficients (γM) were computed in the 0.1 to 0.2 range at 2.1 mol/kg ionic strength, then by 5.7 mol/kg ionic strength, they rose to 0.2 for Ba(2+), 0.6 for Sr(2+), 0.8 for Ca(2+), and 2.1 for Mg(2+). Concurrently, the [Formula: see text] was 0.02-0.03; and [Formula: see text] was 0.01-0.02. While employing these Pitzer-derived activity coefficients, the authors then used the PHREEQC model to characterize precipitation of several of these sulfates and carbonates from actual hydrofracturing waters. Modeled precipitation matched quite well with actual laboratory experiments and full-scale operations. Also, the authors found that SrSO4 effectively co-precipitated radium from hydrofracturing brines, as discerned when monitoring (228)Ra and other beta-emitting species via liquid scintillation; and also when monitoring gamma emissions from (226)Ra.


Subject(s)
Hydraulic Fracking , Models, Chemical , Chemical Precipitation , Osmolar Concentration , Sulfates , Water Pollutants, Radioactive
14.
Water Res ; 68: 784-92, 2015 Jan 01.
Article in English | MEDLINE | ID: mdl-25462782

ABSTRACT

The authors have developed a kinetic dye test protocol that aims to predict the competitive adsorption of 2-methylisoborneol (MIB) to granular activated carbons (GACs). The kinetic dye test takes about two hours to perform, and produces a quantitative result, fitted to a model to yield an Intraparticle Diffusion Constant (IDC) during the earlier times of dye sorption. The dye xylenol orange was probed into six coconut-based GACs and five bituminous-based GACs that hosted varied pore distributions. Correlations between xylenol orange IDCs and breakthrough of MIB at 4 ppt in rapid small-scale column tests (RSSCTs) were found with R²s of 0.85 and 0.95 for coconut carbons that processed waters with total organic carbon (TOCs) of 1.9 and 2.2 ppm, respectively, and with an R² of 0.94 for bituminous carbons that processed waters with a TOC of 2.5 ppm. The author sought to study the influence of the pore sizes, which provide the adsorption sites and the diffusion conduits that are necessary for the removal of those compounds. For coconut carbons, a linear correlation was established between the xylenol orange IDCs and the volume of pores in the range of 23.4-31.8 Å widths (R² = 0.98). For bituminous carbons, best correlation was to pores ranging from 74 to 93 Å widths (R² = 0.94). The differences in adsorption between coconut carbons and bituminous carbons have been attributed to the inherently dissimilar graphene layering resulting from the parent materials and the activation processes. When fluorescein dye was employed in the kinetic dye tests, the correlations to RSSCT-MIB performance were not as high as when xylenol orange was used. Intriguingly, it was the same pore size ranges that exhibited the strongest correlation for MIB RSSCT's, xylenol orange kinetics, and fluoroscein kinetics. When methylene blue dye was used, sorption occurred so rapidly as to be out of the scope of the IDC model.


Subject(s)
Camphanes/chemistry , Charcoal/chemistry , Phenols/chemistry , Sulfoxides/chemistry , Water Pollutants, Chemical/chemistry , Adsorption , Carbon/chemistry , Coal , Cocos/chemistry , Diffusion , Fluorescent Dyes/chemistry , Hydrogen-Ion Concentration , Kinetics , Methylene Blue/chemistry , Models, Theoretical , Particle Size , Porosity , Reproducibility of Results , Time Factors , Water Purification/instrumentation , Water Purification/methods
15.
Water Res ; 56: 214-24, 2014 Jun 01.
Article in English | MEDLINE | ID: mdl-24681276

ABSTRACT

This activated carbon research appraised how pore size and empty-bed contact time influenced the removal of methyl tert-butyl ether (MTBE) at part-per-billion (ppb) concentrations when MTBE was the sole organic impurity. The study compared six granular activated carbons (GACs) from three parent sources; these GACs contained a range of pore volume distributions and had uniform slurry pHs of 9.7-10.4 (i.e. the carbons' bulk surface chemistries were basic). Several of these activated carbons had been specifically tailored for enhanced sorption of trace organic compounds. In these tests, MTBE was spiked into deionized-distilled water (∼pH 7); MTBE loading was measured by isotherms and by rapid small-scale column tests (RSSCTs) that simulated full-scale empty-bed contact times of 7, 14, and 28 min. The results showed that both ultra-fine micropores and small-diameter mesopores were important for MTBE adsorption. Specifically, full MTBE loading during RSSCTs bore a strong correlation (R(2) = 0.94) to the product (mL/g × mL/g) of pore volume ≤4.06 Å wide and pore volume between ∼22 Å and ∼59 Å wide. This correlation was greater than for the product of any other pore volume combinations. Also, this product exhibited a stronger correlation than for just one or the other of these two pore ranges. This multiplicative relationship implied that both of these pore sizes were important for the optimum GAC performance of these six carbons (i.e. favorable mass transfer coupled with favorable sorption). The authors also compared MTBE mass loading during RSSCTs (µg MTBE/g GAC) to isotherm capacity (µg MTBE/g GAC). This RSSCT loading "efficiency" ranged from 28% to 96% for the six GACs; this efficiency correlated most strongly to pores that were 14-200 Å wide (R(2) = 0.94). This correlation indicated that only those carbons with a sufficient volume of 14-200 Å pores could adsorb MTBE to the extent that would be predicted from isotherm data.


Subject(s)
Carbon/chemistry , Methyl Ethers/chemistry , Water Pollutants, Chemical/chemistry , Adsorption , Water Purification/methods
16.
J Environ Manage ; 116: 107-12, 2013 Feb 15.
Article in English | MEDLINE | ID: mdl-23295677

ABSTRACT

The mechanism for the removal of Zn(II) by using coal mine drainage sludge (CMDS) was investigated by spectroscopic analysis and observations of batch tests using model materials. Zeta potential analysis showed that CMDS(25) (dried at 25 °C) and CMDS(550) (dried at 550 °C) had a much lower isoelectric point of pH (pH(IEP)) than either goethite or calcite, which are the main constituents of CMDS. This indicates that the negatively charged anion (sulfate) was incorporated into the structural networks and adsorbed on the surface of CMDS via outer-sphere complexation. The removal of Zn(II) by CMDS was thought to be primarily caused by sulfate-complexed iron (oxy)hydroxide and calcite. In particular, the electrostatic attraction of the negatively charged functional group, FeOH-SO(4)(2-), to the dissolved Zn(II) could provide high removal efficiencies over a wide pH range. Thermodynamic modeling and Fourier transform infrared spectroscopy (FT-IR) demonstrated that ZnSO(4) is the dominant species in the pH range 3-7 as the sulfate complexes with the hydroxyl groups, whereas the precipitation of Zn(II) as ZnCO(3) or Zn(5)(CO(3))(2) (OH)(6) through the dissolution of calcite is the dominant mechanism in the pH range 7-9.6.


Subject(s)
Coal Mining , Water Pollutants, Chemical/metabolism , Ferric Compounds/chemistry , Hydrogen-Ion Concentration , Iron Compounds/chemistry , Minerals/chemistry , Sewage , Spectroscopy, Fourier Transform Infrared , Water Pollutants, Chemical/chemistry , Zinc/chemistry , Zinc/metabolism
17.
J Hazard Mater ; 215-216: 122-8, 2012 May 15.
Article in English | MEDLINE | ID: mdl-22421342

ABSTRACT

A series of pilot-scale tests were conducted with a continuous system composed of a stirring tank reactor, settling tank, and sand filter. In order to treat acidic drainage from a Pb-Zn mine containing high levels of heavy metals, the potential use of coal-mine drainage sludge (CMDS) was examined. The pilot-scale tests showed that CMDS could effectively neutralize the acidic drainage due to its high alkalinity production. A previous study revealed that calcite and goethite contained in CMDS contributed to dissolutive coprecipitation and complexation with heavy metals. The continuous system not only has high removal efficiencies (97.2-99.8%), but also large total rate constants (K(total), 0.21-10.18h(-1)) for all heavy metals. More specifically, the pilot system has a much higher Zn(II) loading rate (45.3gm(-3)day(-1)) than other reference systems, such as aerobic wetland coupled with algal mats and anoxic limestone drains. The optimum conditions were found to be a CMDS loading of 280gL(-1) and a flow rate of 8Lday(-1), and the necessary quantity of CMDS was 91.3gL(-1)day(-1), as the replacement cycle of CMDS was determined to be 70 days.


Subject(s)
Coal Mining , Industrial Waste , Metals, Heavy/chemistry , Refuse Disposal/methods , Water Pollutants, Chemical/chemistry , Calcium Carbonate/chemistry , Ferric Compounds/chemistry , Iron Compounds/chemistry , Minerals/chemistry
18.
Environ Sci Technol ; 45(19): 8529-35, 2011 Oct 01.
Article in English | MEDLINE | ID: mdl-21866938

ABSTRACT

Demonstration-scale metal pouring emission tests and bench-scale Curie-point pyrolysis emission tests were conducted to identify and quantify the hazardous air pollutant (HAP) emissions of five kinds of casting materials, namely, bituminous coal, cellulose, conventional phenolic urethane binder (PUB), naphthalene-depleted PUB, and a collagen-based binder. For a given casting material, the major HAP species generated in Curie-point pyrolysis were essentially the same as those generated in demonstration-scale metal pouring. The 8-10 HAP species identified in the Curie-point pyrolysis tests comprised 65-98% (by weight) of the total HAP emissions quantified in the demonstration-scale pouring emission tests. Furthermore, with these two protocols, we appraised the relative emission changes that would be associated with (a) replacing conventional PUB with collagen-based binder, (b) replacing conventional PUB with naphthalene-depleted PUB, and (c) replacing bituminous coal with cellulose for making sand molds or cores in the casting process. The relative emission changes associated with the use of alternative casting materials exhibited similar trends for most of the major HAP species in the demonstration-scale pouring and Curie-point pyrolysis emission tests. The results indicated that Curie-point pyrolysis emission test could be employed as a convenient and cost-effective screening tool to identify the major HAP species and to compare the relative HAP emission levels for various casting materials.


Subject(s)
Air Pollutants/analysis , Environmental Monitoring/methods , Hazardous Waste/analysis , Metallurgy/methods , Metals/chemistry , Temperature , Benzene/analysis , Urethane/chemistry
19.
Environ Sci Technol ; 45(7): 3062-8, 2011 Apr 01.
Article in English | MEDLINE | ID: mdl-21366305

ABSTRACT

An alternative fuel to replace foundry coke in cupolas was developed from waste anthracite fines. Waste anthracite fines were briquetted with Si-containing materials and treated in carbothermal (combination of heat and carbon) conditions that simulated the cupola preheat zone to form silicon carbide nanowires (SCNWs). SCNWs can provide hot crushing strengths, which are important in cupola operations. Lab-scale experiments confirmed that the redox level of the Si-source significantly affected the formation of SiC. With zerovalent silicon, SCNWs were formed within the anthracite pellets. Although amorphous Si (+4) plus anthracite formed SiC, these conditions did not transform the SiC into nanowires. Moreover, under the test conditions, SiC was not formed between crystallized Si (+4) and anthracite. In a full-scale demonstration, bricks made from anthracite fines and zerovalent silicon successfully replaced a part of the foundry coke in a full-scale cupola. In addition to saving in fuel cost, replacing coke by waste anthracite fines can reduce energy consumption and CO2 and other pollution associated with conventional coking.


Subject(s)
Energy-Generating Resources , Industrial Waste/analysis , Metallurgy/instrumentation , Silicon Compounds/chemistry , Waste Management/methods , Carbon Compounds, Inorganic/chemistry , Coke/analysis , Incineration , Metallurgy/methods
20.
Water Res ; 43(15): 3849-61, 2009 Aug.
Article in English | MEDLINE | ID: mdl-19592065

ABSTRACT

Rapid small-scale column tests (RSSCTs) examined the removal of 29 endocrine disrupting compounds (EDCs) and pharmaceutical/personal care products (PPCPs). The RSSCTs employed three lignite variants: HYDRODARCO 4000 (HD4000), steam-modified HD4000, and methane/steam-modified HD4000. RSSCTs used native Lake Mead, NV water spiked with 100-200 ppt each of 29 EDCs/PPCPs. For the steam and methane/steam variants, breakthrough occurred at 14,000-92,000 bed volumes (BV); and this was 3-4 times more bed volumes than for HD4000. Most EDC/PPCP bed life data were describable by a normalized quantitative structure-activity relationship (i.e. QSAR-like model) of the form: where TPV is the pore volume, rho(mc) is the apparent density, CV is the molecular volume, C(o) is the concentration, (8)chi(p) depicts the molecule's compactness, and FOSA is the molecule's hydrophobic surface area.


Subject(s)
Endocrine Disruptors/analysis , Household Products/analysis , Pharmaceutical Preparations/analysis , Quantitative Structure-Activity Relationship , Water Pollutants, Chemical/analysis , Adsorption/drug effects , Charcoal/chemistry , Endocrine Disruptors/chemistry , Models, Chemical , Pharmaceutical Preparations/chemistry , Water Pollutants, Chemical/chemistry , Water Purification/methods
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