Determination of Cations and Anions in Desulfurization Waste Water of Coal-Fired Power Plant by Ion Chromatography.

The reliable and accurate determination of corrosive anions at sub- to low-µg/L levels is a challenging analytical problem. In this manuscript, a simultaneous determination method of cations and anions in power plant water samples was established by large volume injection ion chromatography. The analytical parameters including separation column, the suppressor current and the elute concentration were optimized. Results showed good separation under the optimum conditions, and the calibration curves of all analytes were linear with good coefficient of determination (r2) >0.997, and the mean recoveries for all analytes ranged from 75.62 to 118.58% with RSD of 0.07-4.83%. The established method was successfully applied to determine the cations and anions in realwaste water samples from coal-fired power, and was verified by inductively coupled plasma optical emission spectrometry and electrometric titration. The relative deviation between methods was all below 6.72%, which indicated good accuracy of the established ion chromatography method. The results could also provide reference for the precise and rapid detection of cations and anions in environmental water samples.

Study on the role of AlOOH in fluorescence correction and depth purification of Cyclops water.

Protein-like substances produced by biochemical reactions after disinfection of Zooplankton like Cyclops and humic substances in natural water are the main components of NOM (Natural organic matter). To eliminate early warning interference in the fluorescence detection of organic matter in natural water, a clustered flower-like AlOOH (aluminum oxide hydroxide) sorbent was prepared. HA (humic acid) and amino acids were selected as mimics of humic substances and protein-like substances in natural water. The results demonstrate that the adsorbent can selectively adsorb HA from the simulated mixed solution and restore the fluorescence properties of tryptophan and tyrosine. Based on these results, a stepwise fluorescence detection strategy was developed and used in natural water rich in zooplanktonic Cyclops. The results show that the established stepwise fluorescence strategy can well overcome the interference caused by fluorescence quenching. The sorbent was also used for water quality control to enhance coagulation treatment. Finally, trial runs of the water plant demonstrated its effectiveness and suggested a potential control method for early warning and monitoring of water quality.

Pilot-scale study on seeded precipitation assisted nanofiltration for flue-gas desulfurization wastewater softening.

In order to reduce the cost of chemical softening, the seeded precipitation assisted nanofiltration (NF) process was introduced into zero liquid discharge (ZLD) of flue-gas desulfurization (FGD) wastewater treatment. A pilot-scale system was developed and run for 168 h in a coal-fired power plant. The system mainly consists of lime softening, ambient temperature crystallizer (ATC) and NF, in which the raw water treatment capacity was 1 m3/h. The results indicated that the system operated stably, the softening cost was 13.30 RMB/m3, and the electricity cost was 3.39 RMB/m3 for the FGD wastewater in this pilot system. High quality gypsum was got from the ATC unit, of which the purity was 95.8%. Through this system, the hardness removal rate was higher than 98.9% and the water recovery rate reached 96%. In addition, the pressure and permeate flux kept stable in the ultrafiltration (UF) unit and NF unit, indicating no scaling occurred in the two units during 168 h test. Thus, a feasible and cost-effective process was provided by using the seeded precipitation assisted NF to deal with the FGD wastewater.

Parallel-slipped π-π electron-donor-acceptor in adsorption process: Molecular dynamics simulation.

Molecular dynamics simulation was used to study the adsorption of single wall carbon nanotubes (SCNT) in levofloxacin (LEV) solutions of different concentrations by Radial distribution function, mean square displacement and interaction energy. The results showed that levofloxacin molecules were adsorbed around the carbon nanotubes. The adsorption effect of large concentration solution was not as good as that of low concentration solution because of agglomeration. LEV molecules with different concentration were free diffusion within 15ns, and gradually agglomerated under the influence of adsorption. The energy change is proportional to the concentration of the molecule. The distance between benzene rings corresponding to the agglomeration effect of levofloxacin molecules was 0.4 nm, which should be the effect of parallel-slipped π-π electron-donor-acceptor (EDA) interactions. The simulation results are valuable to study the adsorption and removal of benzenes by adsorbent.

Insights on the mechanism of Fe doped ZnO for tightly-bound extracellular polymeric substances tribo-catalytic degradation: The role of hydration layers at the interface.

The control of interfacial microbial pollution is of great significance for water safety. Herein, the tribo-catalysis ability of zinc oxide (ZnO) has been investigated, which can realize the control of tightly-bound extracellular polymeric substances (T-EPS) in water under dark environment. The DFT calculation proves the Fe doping introduces the impurity level and decreases the work function from 5.071 eV to 5.045 eV, improves the charge separation of ZnO, and eventually enhances the catalytic reaction efficiency. Characterizing the catalytic reaction process by three-dimensional fluorescence (3D EEM) and fluorescence regional integration (FRI) method, it is found that the T-EPS solution can be degraded 75.8% by Fe-ZnO in 12 min, while ZnO can only degrade 32.2%. Combining with high-resolution scanning probe microscope (HR-SPM) and attenuated total reflection method (ATR-FTIR), hydration layers consist with hydroxyl layer (∼0.23 nm) and water molecular layer (∼0.27 nm) are observed at the interface between Fe-ZnO and T-EPS solution, and terminal hydroxyl group (OHt) is considered to be the active site for the generation of radicals. This study provides an idea for exploring the mechanism of tribo-catalytic reaction and shows its application prospect in the field of microbial inhibition in water.

Synthesis of macroporous silica biomass nanocomposite based on XG/MgSiO3 for the removal of toxic ions.

Biomass is known as a low-cost adsorbents and there is a need for the development of synthesis method further increase its efficient applications. In this work, a macroporous nanocomposite biomass was synthesized by natural polymer (Xanthan gum) and silicate. The resulting nanocomposite was characterized with XRD, SEM, TEM, BET and FTIR. The analysis confirmed that the functions silicate groups were successfully introduced and the nanocomposite not only showed a special macroporous structure but also showed a better cation exchange capacity which helps to retain cation ions. What's more, in order to investigate the adsorption capacity of the biomass, adsorption experiments were considered. The experiment results revealed that nanocomposite showed a high-efficiency adsorption capacity to remove toxic ions such as arsenic, chromium, mercury and cadmium.

Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: kinetics and equilibrium isotherms study.

In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir-Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration.

Adsorption and bio-sorption of nickel ions and reuse for 2-chlorophenol catalytic ozonation oxidation degradation from water.

This work explored the preparation of an effective and low-cost catalyst and investigated its catalytic capacity for 2-chlorophenol ozonation oxidation degradation in wastewater by using an ozone oxidation batch reactor. The catalyst was directly prepared by the reuse of fly ash and sawdust after saturated adsorption of nickel ions from wastewater, which was proposed as an efficient and economic approach. The obtained catalyst was characterized by TGA, BET, FTIR, XRD, and SEM, the results showed that fly ash as the basic framework has high specific surface area and the addition of sawdust as the porogen agent could improve the pore structure of the catalyst. The adsorption of nickel ions by fly ash and sawdust from aqueous solution was also investigated in this study. The results obtained from the experiments indicated that adsorption of nickel ions by fly ash and biomass sawdust could be well described by Langmuir isotherm model and pseudo second order kinetic model. The catalytic performance of catalyst was studied in terms of the effect of time, liquid-solid ratio and pH on 2-chlorophenol ozonation degradation. It was found that the catalyst could effectively improve the ozonation reaction rate at pH=7 with a 2:1 liquid-solid ratio. The kinetic study demonstrated that the reaction followed the first order model, and the rate constant increased 267% (0.03-0.1 min(-1)) of 2-chlorophenol ozonation degradation with 5 mmol/L concentration at pH=7.0 compared with ozonation alone.

Adsorption of Pb(II) from glucose solution on thiol-functionalized cellulosic biomass.

Absorbent cotton, wood sawdust, buckwheat hull were thiol-functionalized to facilitate selective adsorption of Pb(II) from glucose solution. Fourier transform infrared (FTIR) spectroscopic analysis confirmed the formation of S-H modifications. While unmodified absorbent cotton had a Pb(II) adsorption capacity of 10.78 mg/g, thiol-modified absorbent cotton was able to adsorb 28.67 mg/g at optimum pH 6.0. The Pb(II) adsorption capacity increased as the concentration of Pb(II) or glucose increased without loss of glucose during the adsorption process. Wood sawdust and buckwheat hull exhibited greater Pb(II) uptake both before and after modification (wood sawdust: 17.03 mg/g and 43.14 mg/g, buckwheat hull: 34.06 mg/g and 44.84 mg/g), because these cellulosic biomass contained more helpful functional groups for metal binding. The results suggested that modified cellulosic biomass might be a promising adsorbent for heavy metal ion uptake in beverage industry.

The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on adsorption of Cr (VI) from aqueous solution.

The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on removal of Cr (VI) from aqueous solution was studied from aspects of structure characteristics, adsorption properties and mechanism discussions. The calcined hydrotalcites (CH-Mg/Al and CH-Mg/Al/Fe) were obtained by thermal decomposition of their corresponding precursors and characterized by XRD, TEM, pH(PZC) and FTIR. The adsorption properties were studied as a function of pH, initial Cr (VI) concentration and contact time. The results showed that the nature of adsorption is endothermic and spontaneous for both CH-Mg/Al and CH-Mg/Al/Fe, but the thermodynamic parameter value changes revealed the addition of Fe(3+) is disadvantage to adsorption process and the theoretical saturated adsorption capacity decreased by approximately 10.2mg/g at tested temperatures. The removal mechanism involved not only intercalation but adsorption on external surface of the layers and interlayer anion exchange for both CH-Mg/Al and CH-Mg/Al/Fe. Furthermore, the results also indicated that intercalation accounts for a large proportion during removal process whatever for CH-Mg/Al, or for CH-Mg/Al/Fe. Additionally, the replacement of Al(3+) by Fe(3+) in CH-Mg/Al led to the interlayer anion exchange more difficult. On the basis of the results, it is concluded that the existence of ferric iron in calcined Mg/Al hydrotalcite is unfavorable to removal of Cr (VI) from aqueous solution.

Adsorption kinetic character of copper ions onto a modified chitosan transparent thin membrane from aqueous solution.

A modified chitosan transparent thin membrane (MCTTM) was prepared and used as the adsorbent to investigate the adsorption kinetics due to excellent capacity of removing copper ions in water solution. The structure and morphology of MCTTM were characterized by SEM analysis and FTIR analysis. External mass transfer, intra particle diffusion, and pseudo-first and pseudo-second order models were used to describe the adsorption process. The results obtained from the study illustrated that the adsorption process could be described by the pseudo-second order model, which indicated adsorption process was a chemical adsorption behavior of chelation ion exchange proved by the FTIR and adsorption free energy analysis. External mass transfer and intra particle diffusion processes were the rate-controlling steps.