Role of grinding method on granular activated carbon characteristics.

A coconut shell (AC1230CX) and a bituminous coal based (F400) granular activated carbon (GAC) were ground with mortar and pestle (MP), a blender, and a bench-scale ball milling unit (BMU). Blender was the most time-efficient for particle size reduction. Four size fractions ranging from 20 × 40 to 200 × 325 were characterized along with the bulk GACs. Compared to bulk GACs, F400 blender and BMU 20 × 40 fractions decreased in specific surface area (SSA, -23% and -31%, respectively) while smaller variations (-14% to 5%) occurred randomly for AC1230CX ground fractions. For F400, the blender and BMU size fraction dependencies were attributed to the combination of (i) radial trends in the F400 particle properties and (ii) importance of shear (outer layer removal) versus shock (particle fracturing) size reduction mechanisms. Compared to bulk GACs, surface oxygen content (At%-O1s) increased up to 34% for the F400 blender and BMU 20 × 40 fractions, whereas all AC1230CX ground fractions, except for the blender 100 × 200 and BMU 60 × 100 and 100 × 200 fractions, showed 25-29% consistent increases. The At%-O1s gain was attributed to (i) radial trends in F400 properties and (ii) oxidization during grinding, both of which supported the shear mechanism of mechanical grinding. Relatively small to insignificant changes in point of zero charge (pHPZC) and crystalline structure showed similar trends with the changes in SSA and At%-O1s. The study findings provide guidance for informed selection of grinding methods based on GAC type and target particle sizes to improve the representativeness of adsorption studies conducted with ground GAC, such as rapid small-scale column tests. When GACs have radial trends in their properties and when the target size fraction only includes larger particle sizes, manual grinding is recommended.

Anion Exchange Resin and Inorganic Anion Parameter Determination for Model Validation and Evaluation of Unintended Consequences during PFAS Treatment.

When implementing anion exchange (AEX) for per- and polyfluoroalkyl substances treatment, temporal drinking water quality changes from concurrent inorganic anion (IA) removal can create unintended consequences (e.g., corrosion control impacts). To understand potential effects, four drinking water-relevant IAs (bicarbonate, chloride, sulfate, and nitrate) and three gel-type, strong-base AEX resins were evaluated. Batch binary isotherm experiments provided estimates of IA selectivity with respect to chloride ( K x ∕ C ) for IA/resin combinations where bicarbonate < sulfate ≤ nitrate at studied conditions. A multi-IA batch experiment demonstrated that binary isotherm-determined K x ∕ C values predicted competitive behavior. Subsequent column experiments with and without natural organic matter (NOM) allowed for the validation of a new ion exchange column model (IEX-CM; https://github.com/USEPA/Water_Treatment_Models). IA breakthrough was well-simulated using binary isotherm-determined K x ∕ C values and was minimally impacted by NOM. Initial AEX effluent water quality changes with corrosion implications included increased chloride and decreased sulfate and bicarbonate concentrations, resulting in elevated chloride-to-sulfate mass ratios (CSMRs) and Larson ratios (LRs) and depressed pH until the complete breakthrough of the relevant IA(s). IEX-CM utility was further illustrated by simulating the treatment of low-IA source water and a change in the source water to understand the resulting duration of changes in IAs and water quality parameters.

Effect of rhamnolipids on the fungal elimination of toluene vapor in a biotrickling filter under stressed operational conditions.

The application of rhamnolipids in a fungal-cultured biotrickling filter (BTF) has a significant impact on toluene removal. Two BTFs were used; BTF-A, a control bed, and BTF-B fed with rhamnolipids. The effect of empty bed residence times (EBRTs) on toluene bioavailability was investigated. Removal of toluene was carried out at EBRTs of 30 and 60 s and inlet loading rates (LRs) of 23-184 g m-3 h-1. At 30 s EBRT, when inlet LR was increased from 23 to 184 g m-3 h-1, the removal efficiency (RE) decreased from 93% to 50% for the control bed, and from 94% to 87% for BTF-B. Increasing the EBRT simultaneously with inlet LRs, confirms that BTF-A was diffusion-limited by registering a RE of 62% for toluene inlet LR of 184 g m-3 h-1, whereas BTF-B, achieved RE > 96%, confirming a significant improvement in toluene biodegradability. Overall, the best performance was observed at 60 s EBRT and inlet LR of 184 g m-3 h-1, providing a maximum elimination capacity (EC) of 176.8 g m-3 h-1 under steady-state conditions. While a maximum EC of 114 g m-3 h-1 was observed under the same conditions in the absence of rhamnolipids (BTF-A). Measurements of critical micelle concentration showed that 150 mg L-1 of rhamnolipids demonstrated the lowest aqueous surface tension and maximum formation of micelles, while 175 mg L-1 was the optimum dose for fungal growth. Production rate of carbon dioxide, and dissolved oxygen contents highlighted the positive influence of rhamnolipids on adhesive forces, improved toluene mineralization, and promotion of microbial motility over mobility.

Effect of colloid-size copper-based pesticides and wood-preservatives against microbial activities of Gram-positive Bacillus species using five-day biochemical oxygen demand test.

Copper-based pesticides and wood preservatives could end up in the environment during production, use, and end-of-life via different pathways that could cause unintended ecological and adverse health effects. This paper provides the effect of colloid-size Cu-based pesticides (CuPRO and Kocide), micronized Cu azole (MCA-1 and MCA-2) and alkaline Cu quaternary (ACQ) treated woods, Cu2+, Cu2+ spiked untreated wood (UTW), and CuCO3 solutions against Gram-positive Bacillus species using five-day biochemical oxygen demand (BOD5) standard test. The total Cu leached from MCA-1, MCA-2, and ACQ in Milli-Q water after 5 days were ~0.1, ~0.11, and ~0.64 g/kg of wood, respectively. However, the form of Cu leached from MCA woods was mostly ionic (> 90%). The total organic carbon (TOC) content of any tested wood (UTW/MCA-1/MCA-2/ACQ) was ~99% of its corresponding total carbon (TC) content, whereas the TOC of any tested wood sawdust exceeded that of its corresponding piece/block by > 300%. The dissolved oxygen (DO) consumption value in the presence of Cu2+, CuCO3, CuPRO, and Kocide solutions was significantly influenced by Cu particles/ions. However, the DO consumption value in the presence of UTW/MCA-1/MCA-2/ACQ woods was significantly influenced by organics leached from woods. On the other hand, the DO consumption of MCA sawdust was greater than (300%) that of MCA pieces/block. The findings of this study provide more insight into how organics leached from woods significantly reduce the toxic effects of Cu ions against Gram-positive Bacillus species.

Trace and Major Elements Concentration in Fish and Associated Sediment-Seawater, Northern Shores of the Persian Gulf.

The concentration of 19 metal and non-metal elements in two fishes (Liza subviridis and Sphyraena jello) and associated sediment-seawater from the northern part of the Persian Gulf was measured. The samples were gathered from two industrial ports, one commercial port, and one residential port. The metal accumulation in the muscle and liver of fishes was evaluated. Nickel (mean 362.07-712.83 µg/g) and chromium (mean 470.00-691.47 µg/g) in sediment and zinc (mean 9.01-31.15 µg/L) and arsenic (mean 18.22-22.14 µg/L) in seawater had the most abundancy among studied elements. The accumulation of elements in S. jello (a pelagic species) was higher than L. subviridis (a demersal species). For both species, major elements of S and Mg and trace elements of Fe, Al, Si, Zn, and Cu showed highest accumulation. Also, fish samples from Emam Hassan Port were more contaminated than other stations. Ecological indexes values have revealed a low to moderate elemental pollution of sediment and fish samples in the north part of the Persian Gulf.

Effect of surfactin on removal of semi-volatile organic compound: Emphasis on enhanced biofiltration performance.

The performance of a lab-scale biotrickling filter (BTF) inoculated with a mixed fungal consortium was investigated for the simultaneous abatement of 2-ethylhexanol; a hydrophobic semi-volatile organic compound (SVOC), and propylene glycol monomethyl ether (PGME). The BTF performance was investigated in the presence of lipopeptide-type biosurfactant, surfactin. The effect of surfactin on the removal efficiency and elimination capacity was examined at stretched inlet loading rates (LR): 1.04 to 15.7 and 3.2-48 g m-3 h-1 of PGME and 2-ethylhexanol, respectively. Seeding the BTF with 50 mg L-1 of surfactin maintained high and consistent removal efficiencies of PGME and 2-ethylhexanol up to LRs of 15.7 and 32 g m-3 h-1, with removal efficiencies of 98.5 and 99%, respectively. Once the LR of 2-ethylhexanol increased to 48 g m-3 h-1, a substrate inhibition was observed, accompanied by a sudden decrease in removal efficiency from 99.2 to 62.3%. At the same LR, the BTF performance was improved by reseeding 100 mg L-1 of surfactin, hence, reinstated the removal efficiency of 2-ethylhexanol to 92.7% and achieving a maximum elimination capacity of 44.5 g m-3 h-1. This enhanced SVOC uptake rate was further confirmed by a considerable increase in reaction rate constant from 0.005 to 0.017 s-1. A batch study was also conducted at the end of the experimental run to better understand the correlation between surfactin concentrations and the time-dependent partition coefficient of 2-ethylhexanol. Biofilm microbial community structure revealed relative abundancy of 72 and 28% of Trichoderma asperellum and Fusarium solani, respectively. The findings of this study show for the first time that the removal of a semi-VOC such as 2-ethylhexanol is feasible in the presence of surfactin and hence improving the bioavailability of hydrophobic semi-VOC.

Microplastics accumulation in sediments and Periophthalmus waltoni fish, mangrove forests in southern Iran.

This investigation was aimed to identify microplastics in the sediment and mudskipper fish (Periophthalmus waltoni) in mangrove forests in southern Iran. Sediments and mudskipper samples were collected at high, mid, and low tidal points of five stations. A total of 2657 plastic particles in different size, color, shape, and genera were identified from sediment samples and 15 microplastic were isolated from mudskippers. The highest and lowest abundance of isolated microplastics from sediments was observed in mangrove forests of Bidkhoun (urban area) and Bordkhon, respectively while no microplastics were found in the fish tissue in those stations. The black (60%) and white (7%) color microplastics in the mudskipper had the highest and the lowest frequency. The highest and lowest polymers in mangrove forest sediments were corresponded to polystyrene (26%) and polycarbonate (3%), respectively. Raman and Fourier transform infrared spectroscopy (FT-IR) techniques were used to identify the type of the polymer. Most of the microplastics found were made of polystyrene, polypropylene, and polyethylene terephthalate. The type of studied area and texture of sediment separately affected the frequency of microplastic and mesoplastic (P-value <0.05) in the sediment samples. The abundance of microplastics in the sediment samples of the Bidkhoun mangrove forest was higher than other studied stations due to proximity to urban and industrial areas. The findings of this study raised concerns about microplastic pollution in the mangrove forests of southern Iran, a threat to the ecosystem and public health, which requires careful actions to prevent and diminish its adverse effects.

Design and evaluation of degassed anaerobic membrane biofilm reactors for improved methane recovery.

Anaerobic treatment of domestic wastewater (DWW) produces dissolved methane that needs to be recovered for use as an energy product. Membrane-based recovery systems have been reported in the literature but are often limited by fouling. The objective of this study was to develop a methane producing biofilm on the shell side surface a membrane to allow for immediate recovery of methane as it was produced, negating mass transfer resistance caused by fouling. Between 89 and 96% of total methane produced was recovered via in-situ degassing without the need for fouling control or cleaning throughout 72 weeks of operation. High methane recovery efficiencies led to predictions of net positive energy yield in one reactor and a 32-61% reduction in energy demand in the others compared to the control. This research demonstrates the feasibility and usefulness of combining attached growth anaerobic wastewater treatment processes with hollow fiber membrane methane recovery systems for improved operation.

Role of water chemistry on stability, aggregation, and dissolution of uncoated and carbon-coated copper nanoparticles.

Intentional or accidental release of copper nanoparticles (Cu-NPs) from consumer products during manufacturing, use, and end-of-life management could pose health and ecological risks. This paper presents a detailed study on the role of water chemistry on the fate of uncoated and carbon-coated Cu-NPs dispersed in aqueous cetyltrimethylammonium bromide (CTAB) surfactant in the presence and absence of humic acids (HAs). A range of water chemistry and HAs had minimum impact on hydrodynamic diameter and zeta-potential values of uncoated and carbon-coated Cu-NPs. The water pH significantly (p < 0.001) affected the aggregation of uncoated Cu-NPs unlike that of carbon-coated Cu-NPs; however, the presence of HAs increased the stability of uncoated Cu-NPs. Although CTAB is considered as an efficient dispersant to stabilize Cu-NPs, the effect descended with time for uncoated Cu-NPs. The dissolution of Cu over time decreased with increasing pH for both uncoated (0.5-50% weight) and carbon-coated (0.5-40% weight) Cu-NPs. However, carbon-coated Cu-NPs exhibited significant dissolution (p < 0.001) at neutral pH than uncoated Cu-NPs may be due to the additional carbon it acquired during coating. Increasing HAs concentration from 0 to 15 mg L-1 at pH 5.5 inhibited aggregations but enhanced dissolution of the uncoated and carbon-coated Cu-NPs. These findings inform risk analysis of Cu-NPs including how Cu-NPs fate, mobility and bioavailability are modulated by particles coating and dispersant, HAs presence, water chemistry and exposure time in dispersion media.

Influence of chitosan and magnetic iron nanoparticles on chromium adsorption behavior of natural clay: Adaptive neuro-fuzzy inference modeling.

In the current study, the influence of iron oxide nanoparticles and chitosan (CS) on the adsorption capacity of natural clay for chromium removal from aqueous media was explored. Clay-based adsorbents (clay, CS/Clay, Clay/Fe3O4, and CS/Clay/Fe3O4) were manufactured and their physicochemical properties were identified. The effects of operating factors on the adsorption efficiency were optimized. The results showed that the adsorption equilibrium data for the clay, CS/Clay, and Clay/Fe3O4 corresponds to the Langmuir model, while for the CS/Clay/Fe3O4 is consistent with the Freundlich model. The maximum adsorption capacity (qmax) of Cr(VI) using clay, CS/Clay, Clay/Fe3O4 and CS/Clay/Fe3O4 were 63.69 mg/g, 80.30 mg/g, 97.08 mg/g, and 117.64 mg/g, respectively. It was showed that the addition of chitosan and Fe3O4 magnetic nanoparticles to the clay increases its adsorption capacity. The values of ΔG° and ΔH° parameter for Cr adsorption using adsorbents were negative, indicating that the removal process is spontaneous and exothermic. The kinetic behavior obeyed the pseudo-second-order model. The chromium removal process using all the adsorbents had a two-step mechanism. The wastewater of a leather factory was effectively treated using clay based-adsorbents. Based on R2, MSE, SSE, and ARE values, good agreement was observed between the ANFIS model and experimental outcomes.

Influence of water chemistry on colloid-size Cu-based pesticides particles: A case of Cu(OH)2 commercial fungicide/bactericide.

The intensive, widespread, and ever-increasing applications of Cu-based pesticides in agriculture could potentially increase environmental exposures via different routes. Unlike ionic/bulk forms, the fate, transport, and toxicity of colloid-size Cu-based pesticides are not well studied. This paper provides evaluation outcomes of granule and dispersion characterizations, stability, and dissolution of colloid-size particles of Cu(OH)2 commercial pesticide product at a range of water chemistry. The evaluated product contained about 35% weight of metallic Cu equivalent and Cu(OH)2 particles with sizes < 1 µm of which a fraction of nanoscale particles exist. The presence of Ca2+ at ionic strengths of >0.01 M and 0.001-0.2 M significantly influenced (p < 0.001) particle size (PS) and ζ-potential values, respectively at all investigated pH values. Cu dissolution at pH 5.5 was significant (p < 0.001) and exceeded Cu dissolutions at pH 7.0 by 87-90% and at pH 8.5 by 87-95% in all dispersions. The order of Cu dissolution was pH 5.5 > pH 7.0 > pH 8.5 in all dispersions. Cu dissolution was relatively reduced by 53% by increasing HA from 0 to 5 mg L-1 and enhanced by 55% by increasing HA from 5 to 15 mg L-1, however, the overall Cu dissolution was decreased by 27% by increasing HA from 0 to 15 mg L-1. Thus, HAs reduced the dissolution of Cu at pH < 7. The findings provide an insight into how water chemistry influences the fate and transport of colloid-size Cu-based pesticides particles.

Potential of green/brown algae for monitoring of metal(loid)s pollution in the coastal seawater and sediments of the Persian Gulf: ecological and health risk assessment.

The current investigation evaluates metal (loid)s biomonitoring using algae as well as the metal(loid) pollution of seawaters and sediments in the northern part along the Persian Gulf. Algae, seawater, and sediment samples were collected from four coastal areas with different land applications. The concentration of Ni, V, As, and Cd in abiotic samples (seawater and sediment) and four species of algae (Enteromorpha intestinalis, Rhizoclonium riparium, Cystoseira myrica, and Sargassum boveanum) was measured using an ICP-AES device. Concentrations of potentially toxic elements in seawater, sediments, and algae species followed the trend of "Ni˃V˃As˃Cd." The area of Asaloyeh (with the highest industrial activity) and the Dayyer area (with the lowest industrial activity) provided the highest and lowest amounts of metal(loid)s pollution, respectively. The average concentrations of V and As in four algae species significantly differed for all sampled areas. Obtaining the bio-concentration factor (BCF) > 1 for seawater and < 1 for sediment indicated that the studied algae have the ability to efficiently concentrate metal(loid)s from seawater and the limited accumulation of metals in sediments. According to the Nemerow pollution index, the order of metal(loid)s pollution for the studied areas estimated as Asaloyeh>Ganaveh>Bushehr>Dayyer. Algae species of C. myrica and E. intestinalis can often serve as suitable biological tools for monitoring seawater and sediment quality.

Organochlorine pesticides contamination in agricultural soils of southern Iran.

There is limited information about pesticide contamination in Iran's agricultural land, particularly in plains producing exportable fruits. The aim of this investigation was to evaluate the concentration of organochlorine pesticides (OCPs) including hexachlorocyclohexane (HCH), heptachlor, dichloro-diphenyl-trichloroethane (DDT), chlordane (CHL), and their isomers compounds in agricultural soils of southern Iran. A total of 28 topsoil samples were collected from agricultural lands of Dalaki and Shabankare areas, Bushehr, Iran. In Dalaki area, the mean value of ΣHCH (α, ß, γ, δ), ΣDDT (o,p-DDE, o,p-DDD, o,p-DDT, p,p-DDE, p,p-DDD, p,p-DDT, and DDT), and ΣCHL (Trans-chlordane, Cis-chlordane, Heptachlor-exo-epoxide, and Heptachlor) was found to be 0.411 ng/g (dry weight, dw), 4.37 ng/g dw, and 2.04 ng/g dw, respectively. In Shabankare area the mean value of ΣHCH, ΣDDT, and ΣCHL was measured to be 1.38 ng/g dw, 11.99 ng/g dw, and 1.62 ng/g dw, respectively. The concentration trend of pesticides in both areas was as follows: DDT > CHL > HCH. Source identification indicated recent usage of HCH and DDT in the studied areas. Obtaining a cis-chlordane/trans-chlordane ratio greater than one in Shabankare farmlands showed that chlordane was not used recently. The health risk assessment showed that children and adults groups in both areas are exposed to negligible cancer risk. More serious attempts are necessary to reduce usage of OCPs during the agricultural process and the protection of soil and human health in the studied areas.

Efficient arsenic(V) removal from contaminated water using natural clay and clay composite adsorbents.

The natural clay is an abundant, accessible, and low-cost material that has the potential for use in the water and wastewater industry. In this paper, Iranian natural clay and clay/Fe-Mn composite were used to remove toxic arsenic from the liquid environment. The natural clay and clay/Fe-Mn composite were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX), X-ray diffractometry (XRD), thermo-gravimetric analysis (TGA), and atomic force microscopy (AFM) techniques. The effects of parameters (initial pH, temperature, sorption dose, and contact time) on the efficiency and behavior of the arsenic(V) adsorption process were studied. Freundlich (R2 = 0.945 and 0.989), Langmuir (R2 = 0.922 and 0.931), modified Langmuir (R2 = 0.921 and 0.929), and Dubinin-Radushkevich (R2 = 0.706 and 0.723) models were fitted to evaluate the equilibrium data of arsenic(V) adsorption process by natural clay and clay/Fe-Mn composite, respectively. The Langmuir adsorption capacity of arsenic(V) by the natural clay and clay/Fe-Mn composite was determined to be 86.86 mg/g and 120.70 mg/g, respectively. The arsenic(V) adsorption process followed the pseudo-second-order model. Negative values of ΔG° and ΔH° showed that the arsenic(V) sorption by the studied materials is thermodynamically spontaneous and exothermic. According to the findings, the natural clay and clay/Fe-Mn are suitable and recyclable sorbents for arsenic(V) adsorption from aqueous solutions. Also, the composite of clay with iron and manganese can improve the efficiency of clay in the removal of arsenic.

Characterization of colloid-size copper-based pesticide and its potential ecological implications.

The intensive use of Cu-based pesticides in agriculture could have an unintended impact on the ecosystems and human health via different exposure pathways. This paper presents the results of experiments involving colloidal stability, aggregation, and dissolution of Cu2O commercial pesticide under various environmental conditions in view of ecological implications. The investigated pesticide contains ∼750 g kg-1 Cu (75% weight of product), Cu2O particles with sizes < 1 µm, and nominal size fraction of Cu2O nanoparticles. The co-presence of Ca2+ (20 mM) and humic acid (HA, 15 mg L-1) significantly modulates (p < 0.001) the colloidal stability and mobility of particles. The dissolution of Cu at pH 5.5 was about 85%, 90%, and 75% weight more than the dissolution of Cu at pH 7.0, pH 8.5, and pH 7.0 and pH 8.5 combined, respectively in all dispersions. However, increasing HA content from 0 to 15 mg L-1 reduced the dissolution of Cu by 56%, 50%, and 40% weight at pH 5.5, 7.0, and 8.5, respectively. Thus, pH below 7.0 is a critical factor to control the dissolution and bioavailability of Cu that may pose ecotoxicity and environmental pollution, whereas pH above 7.0 and the presence of HA attenuate the pH effect. These findings provide insight into how the potential mobility and bioavailability of Cu is modulated by the water chemistry under various environmental scenarios and media.

Effectiveness of biosurfactant for the removal of trihalomethanes by biotrickling filter.

In this study, the biodegradation of a mixture of two trihalomethane (THM) compounds, chloroform (CF) and dichlorobromomethane (DCBM), was evaluated using two laboratory-scale biotrickling filters (BTFs). The two BTFs, hereby designated as "BTF-A" and "BTF-B," were run parallel and used ethanol as co-metabolite at different loading rates (LRs), and a lipopeptide-type biosurfactant that was generated by the gram-positive bacteria, Surfactin, respectively. The results using BTF-A showed that adding ethanol at a higher rate of 4.59 g/(m3 h) resulted in removal efficiencies of 85% and 87% for CF and DCBM, respectively. Conversely, for the same LR, the use of Surfactin without ethanol (BTF-B) showed comparable removal efficiencies of 85% and 80% for CF and DCBM, respectively. The maximum rate constant for CF and DCBM for the BTF-A was 0.00203 s-1 and 0.0022 s-1, respectively. For the same THMs LR, similar reaction rate constants resulted for the BTF-B. Further studies were conducted to investigate and understand the microbial diversity within both BTFs. The result indicated that for BTF with co-metabolite, Fusarium sp. was the most dominant fungi over 98% followed by F. Solani with less than 2%. F. oxysporum and Fusarium sp. were instead the dominant fungi for the BTF with Surfactin. Before introducing the Surfactin into the BTF, the batch experiment was conducted to evaluate the effectiveness of synthetic surfactant as compared to a biosurfactant (Surfactin). In this regard, vials with Surfactin showed better performance than vials with Tomadol 25-7 (synthetic surfactant).

Amendment of Caulerpa sertularioides marine alga with sulfur-containing materials to accelerate Cu removal from aqueous media.

This study reports a new approach of alga amendment in a live mode. The Caulerpa sertularioides alga was modified with sulfur-containing materials of methionine (C5H11NO2S) and sodium sulfate (Na2SO4) to more concentrate the sulfur content of the yielded biomass (adsorbent). The simple and amended C. sertularioides alga was fully characterized with FTIR, SEM, EDX, BET, BJH, and pHzpc techniques. The copper adsorption from aqueous media was done by three adsorbents of C. sertularioides-simple (CSS), C. sertularioides-Na2SO4 (CSN), and C. sertularioides-C5H11NO2S (CSC). The parameters of pH (2-6), adsorbent dosage (2-10 g/L), and contact time (3-80 min) were optimized at 5, 5 g/L, and 60 min, respectively. According to Langmuir isotherm (the best-fitted model), the maximum adsorption capacity of CSN (98.04 mg/g) was obtained 2.4 times higher than CSC (40.73 mg/g) and 9.5 times higher than CSS (10.29 mg/g). The Cu adsorption process by the adsorbents was best-fitted pseudo-second-order kinetic model. The CSN, CSC, and CSS biomasses were successfully reused 5, 4, and 4 times, respectively. The thermodynamic study revealed that the copper adsorption process by CSN is exothermic and non-spontaneous. Finally, the suitability of adsorbents prepared from algae was tested by cleaning a simulated wastewater.

Treatment technologies for PAH-contaminated sites: a critical review.

To reduce environmental and human health risks of contaminated sites, having a comprehensive knowledge about the polycyclic aromatic hydrocarbon (PAH) removal processes is crucial. PAHs are contaminants which are highly recognized to pose threats to humans, animals, and plants. PAHs are hydrophobic and own two or more benzene rings, and hence are resistant to structural degradation. There are various techniques which have been developed to treat PAH-contaminated soil. Four distinct processes to remove PAHs in the contaminated soil, thought to be more effective techniques, are presented in this review: soil washing, chemical oxidation, electrokinetic, phytoremediation. In a surfactant-aided washing process, a removal rate of 90% was reported. Compost-amended phytoremediation treatment presented 58-99% removal of pyrene from the soil in 90 days. Chemical oxidation method was able to reach complete conversion for some PAHs. In electrokinetic treatment, researchers have achieved reliable results in removal of some specific PAHs. Researchers' innovations in novel studies and advantages/disadvantages of the techniques are also investigated throughout the paper. Finally, it should be noted that an exclusive method or a combination of methods by themselves are not the key to be employed for remediation of every contaminated site but the field characteristics are also essential in selection of the most appropriate decontamination technique(s). The remedy for selection criteria is based on PAH concentrations, site characteristics, costs, shortcomings, and advantages.

Potential of trees leaf/ bark to control atmospheric metals in a gas and petrochemical zone.

Leaf and bark of trees are tools for assessing the effects of the heavy metals pollution and monitoring the environmental air quality. The aim of this study was to evaluate the presence of Ni, Pb, V, and Co metals in four tree/shrub species (Conocarpus erectus, Nerium oleander, Bougainvillea spectabilis willd, and Hibiscus rosa-sinensis) in the heavily industrial zone of Asaloyeh, Iran. Two industrial zones (sites 1 and 2), two urban areas (sites 3 and 4), and two rural areas (sites 5 and 6) in the Asaloyeh industrial zone and an uncontaminated area as a control were selected. Sampling from leaf and bark of trees was carried out in spring 2016. The metals content in the washed and unwashed leaf and bark was investigated. The results showed that four studied metals in N. oleander, C. erectus, and B. spectabilis willd in all case sites were significantly higher than that of in the control site (p < 0.05). The highest concentration of metals was found in sites 3, 4, and 6; this was due to dispersion of the pollutants from industrial environments by dominant winds. The highest comprehensive bio-concentration index (CBCI) was found in leaf (0.37) and bark (0.12) of N. oleander. The maximum metal accumulation index (MAI) in the samples was found in leaf of N. oleander (1.58) and in bark of H. rosa-sinensis (1.95). The maximum bio-concentration factor (BCF) was seen for cobalt metal in the N. oleander leaf (0.89). The nickel concentration in washed-leaf samples of C. erectus was measured to be 49.64% of unwashed one. In general, the N. oleander and C. erectus species were found to have the highest absorption rate from the atmosphere and soil than other studied species, and are very suitable tools for managing air pollution in highly industrialized areas.

Inhibition of biofilm growth on polymer-MWCNTs composites and metal surfaces.

There is an increased interest in incorporating multi-wall carbon nanotubes (MWCNTs) into polymer matrices to control the adhesion of bacteria to surfaces and the subsequent formation of biofilm growth on the surface of water pipes, food packages, and medical devices. Microbial interactions with carbon nanotube-polymer composites in the environment are not well understood. The growth of Pseudomonas fluorescens (gram-negative) and Mycobacterium smegmatis (gram-positive) biofilms on copper, polyethylene (PE), polyvinyl chloride, and stainless steel was compared with growth on MWCNT-PE composites in order to gain insight into the effect of the surface properties of nanomaterials on the attachment and proliferation of microorganism which could result in the engineering of better, non-fouling materials. A statistical analysis of the biofilm growth showed a significant impact of materials for both P. fluorescens (p < 0.0001) and M. smegmatis (p = 0.00426). Biofilm growth after 56 days on PE compared to biofilm growth on copper surfaces decreased by 46.4% and 34.9% for P. fluorescens and M. smegmatis, respectively. Biofilm growth on PE-multiwall-carbon-nanotubes (MWCNTs)-composites surface compared to PE decreased by 89.3% and 29% for P. fluorescens and M. smegmatis, respectively. Bacterial species (p < 0.0006) and surface roughness (p < 0.0001) were important factors in determining the attachment and initial biofilm growth rate. The interactions between cells and material surface could be attributed to the complicated and collective effect of electrostatic forces, hydrophobic interactions, and hydrogen/covalent bonding. Further study is needed to determine whether or not there is a difference between the cell attachment in the exponential growth phase and the stationary, or decay, phase cells.