MoS2催化活化单过硫酸盐降解有机污染物研究现状

随着城镇化进程加快,大量含难降解有机污染物的工业废水和生活污水因不合理处置而进入水体,对水环境质量造成严重威胁。过渡金属离子催化活化单过硫酸盐(PMS)产生活性氧去除水中难降解有机物的催化体系的研究已有大量文献报道,但存在金属离子二次污染和催化剂难以回收等问题。MoS₂作为优异的二维半导体材料,在储能和催化领域颇具优势并实现产业化生产。在水处理领域,研究发现MoS₂作为非均相金属催化剂能够有效活化PMS去除水中难降解有机物。本文主要综述了MoS₂作为催化剂、金属离子助催化剂或复合型共催化剂活化PMS体系降解水中有机污染物的研究进展,归纳并比较上述催化体系对污染物的降解效能,对催化反应机制进行探讨分析,并针对目前存在的问题提出相关研究展望。      

Nonfoaming adsorptive bubble separation processes

Two nonfoaming separations, bubble fractionation and solvent sublation, are reviewed. These unit operations are interfacial (gas bubble-liquid) separation techniques that have significant potential for the removal of several metal ions and hydrophobic organic compounds of environmental significance from aqueous solutions. Experimental and theoretical work on the two processes relating the effects of process variables are summarized. The underlying mechanisms of the two processes are identical although solvent sublation is found to have significant advantages over bubble fractionation, air stripping, and the related process of solvent extraction. Specifically, sublation can achieve a greater degree of removal than extraction, can remove both volatile and nonvolatile compounds, unlike air stripping, and has less sensitivity to axial dispersion than bubble fractionation. The potential use of these processes for large-scale separations is examined; the limitations and need for further work are clearly evident. Questions of scale-up, bubble generation, and reduction of axial dispersion all require further investigation.     

Photoelectrocatalytic decontamination of oilfield produced wastewater containing refractory organic pollutants in the presence of high concentration of chloride ions

The feasibility study of the application of the photoelectrocatalytic decontamination of high saline produced water containing refractory organic pollutants was investigated in the slurry photoelectrocatalytic reactor with nanometer TiO2 particle prepared with sol-gel method using the acetic acid as hydrolytic catalyst. The efficiency of the photoelectrocatalytic decontamination of produced water was determined with both COD removal from the tested wastewater and the decrease of mutagenic activity evaluated by Ames tests. The experimental results showed that the photoelectrocatalysis is a quite efficient process for decontaminating the produced water, although there are high concentration of salt existed in oilfield wastewater. We found that the COD removal efficiencies by photoelectrocatalytic process are much higher than that of by photocatalytic or electrochemical oxidation individually in the photoelectrocatalytic reactor. The COD removal can be substantially improved by the added H2O2 and the generation of active chlorine from high concentration chlorides in the wastewater. The effects of various operating conditions, such as initial COD concentration, applied cell voltage, catalyst amount and initial pH value of solution, on the photoelectrocatalytic efficiencies, is also investigated in detail. The results showed that when the raw produced wastewater was diluted in a 1:1 (v/v) ratio, there is a highest COD removal efficiency. And the photoelectrocatalytic degradation of organic pollutants in saline water is much favored in acidic solution than that in neutral and/or alkaline solution.     

Study on treatment of coking wastewater by biofilm reactors combined with zero-valent iron process

Experiments were conducted to investigate the behavior of the integrated system with biofilm reactors and zero-valent iron (ZVI) process for coking wastewater treatment. Particular attention was paid to the performance of the integrated system for removal of organic and inorganic nitrogen compounds. Maximal removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH(3)-N) and total inorganic nitrogen (TIN) were up to 96.1, 99.2 and 92.3%, respectively. Moreover, it was found that some phenolic compounds were effectively removed. The refractory organic compounds were primarily removed in ZVI process of the integrated system. These compounds, with molecular weights either ranged 10,000-30,000 Da or 0-2000 Da, were mainly the humic acid (HA) and hydrophilic (HyI) compounds. Oxidation-reduction and coagulation were the main removal mechanisms in ZVI process, which could enhance the biodegradability of the system effluent. Furthermore, the integrated system showed a rapid recovery performance against the sudden loading shock and remained high efficiencies for pollutants removal. Overall, the integrated system was proved feasible for coking wastewater treatment in practical applications.     

Comparative energy efficiency of wastewater treatment technologies: a synthetic index approach

Improving the energy efficiency of wastewater treatment plants (WWTPs) provides notable economic and environmental benefits to society. Several studies have benchmarked the energy performance of WWTPs, but they did not take into account for differences in the wastewater treatment technologies they used, thus obscuring their relative efficiencies in removing harmful pollutants. To overcome this shortcoming, this study assessed and compared the energy efficiencies of five wastewater treatment technologies. To do so, the metafrontier approach was used in order to account for the technological differences among plants in removing pollutants. The results evidenced that energy efficiencies for WWTPs using attached-growth processes were higher than for WWTPs using suspended-growth technologies as secondary treatment. Moreover, higher pollutant removal efficiencies associated with biological removal of nutrients compensated for the higher energy requirements of this technology, making these WWTPs more energy efficient in the removal of pollutants. The results of this study provide essential information for improving the sustainability of current WWTPs and can support decision-making in the planning of new wastewater treatment facilities.     

Study of the aerobic biodegradation of coke wastewater in a two and three-step activated sludge process

A laboratory-scale biological plant composed of two aerobic reactors operating at 35 degrees C was used to study the biodegradation of coke wastewater. The main pollutants to be removed are organic matter, especially phenols, thiocyanate and ammonium nitrogen. The concentrations of the main pollutants in the wastewater during the study ranged between 922 and 1,980 mg COD/L, 133 and 293 mg phenol/L, 176 and 362 mg SCN/L and 123 and 296 mg NH(4)(+)-N/L. The biodegradation of these pollutants was studied employing different hydraulic residence times (HRT) and final effluent recycling ratios in order to minimize inhibition phenomena attributable to the high concentrations of pollutants. During the optimisation of the operating conditions, the removal of COD, phenols and thiocyanate was carried out in the first reactor and the nitrification of ammonium took place in the second. The best results were obtained when operating at an HRT of 98 h in the first reactor and 86 h in the second reactor, employing a recycling ratio of 2. The maximum removal efficiencies obtained were 90.7, 98.9, 98.6 and 99.9% for COD, phenols, thiocyanate and NH(4)(+)-N, respectively. In order to remove nitrate, an additional reactor was also implemented to carry out the denitrification process, adding methanol as an external carbon source. Very high removal efficiencies (up to 99.2%) were achieved.     

Performance evaluation of a biotrickling filter degrading mixtures of hydrophobic and hydrophilic compounds

The removal of a mixture of painting solvents from waste air using a biofiltration process was evaluated in this project. The pollutants removed included hydrophobic (aromatic hydrocarbons) and hydrophilic (water soluble ketones and esters) compounds. A trickle bed reactor with a defined immobilized mixed culture on polyethylene Pall rings was utilized in this biodegradation study. The removal efficiencies (RE) of the individual groups of pollutants during loading experiments were determined. An increase of the aromatic hydrocarbons loading resulted in a drop of their RE_AROM with no effect on the RE value of ketones. The overloading of ketones caused a rapid drop in RE_AROM and a small drop in RE_KET. To achieve a restoration of the biocatalyst degradation properties after the increase in loading, an addition of phosphate to the aqueous medium was implemented which successfully restored the removal efficiency.     

Selection of design parameters and optimization of operating parameters of soybean oil-based bulk liquid membrane for Cu(II) removal and recovery from aqueous solutions

The objectives of this work were to select suitable design parameters and optimize the operating parameters of a soybean oil-based bulk liquid membrane (BLM) for Cu(II) removal and recovery from aqueous solutions. The soybean oil-based BLM consists of an aqueous feed phase (Cu(II) source), an organic membrane phase (soybean oil (diluent), di-2-ethylhexylphosphoric acid (D2EHPA) (carrier) and tributylphosphate (phase modifier)) and an aqueous stripping phase (sulfuric acid solution (H(2)SO(4))). Effects of design parameters (stirring condition and stripping/membrane to feed/membrane interface area ratio) of soybean oil-based BLM on the Cu(II) removal and recovery from aqueous solutions were investigated and the suitable parameters were selected for further studies. Optimization of the operating parameters (D2EHPA concentration, H(2)SO(4) concentration, stirring speed, temperature and operating time) of soybean oil-based BLM for maximum percentage (%) recovery of Cu(II) was then conducted using Response Surface Methodology and the optimum parameters were determined. A regression model for % recovery was developed and its adequacy was evaluated. The experimental % recovery obtained under the optimum operating conditions was compared with the predicted one and they were found to agree satisfactorily with each other.     

Optical and photocatalytic properties of arginine-stabilized cadmium sulfide quantum dots

Currently, environmental pollution caused by organic compounds leads to severe negative consequences in the human society. Therefore, the removal of these pollutants from aqueous media has become one of the most important issues in environmental science. In the present study, CdS QDs were successfully prepared under aqueous conditions using l-arginine as the stabilizing agent. Optical property determination results reveal that the CdS QDs exhibited strong absorption and photoluminescence in a visible wavelength region. Moreover, the CdS QDs could effectively degrade two organic dyes under visible light irradiation. This suggested that the CdS QDs prepared in this work might be used as the potential photocatalyst to effectively treat the organic pollutants under visible light irradiation.     

Artificial neural network modeling in competitive adsorption of phenol and resorcinol from water environment using some carbonaceous adsorbents

This paper illustrates the application of artificial neural network (ANN) for prediction of performances in competitive adsorption of phenol and resorcinol from aqueous solution by conventional and low cost carbonaceous adsorbent materials, such as activated carbon (AC), wood charcoal (WC) and rice husk ash (RHA). The three layer's feed forward neural network with back propagation algorithm in MATLAB environment was used for estimation of removal efficiencies of phenol and resorcinol in bi-solute water environment based on 29 sets of laboratory batch study results. The input parameters used for training of the neural network include amount of adsorbent (g/L), initial concentrations of phenol (mg/L) and resorcinol (mg/L), contact time (h), and pH. The removal efficiencies of phenol and resorcinol were considered as an output of the neural network. The performances of the developed ANN models were also measured using statistical parameters, such as mean error, mean square error, root mean square error, and linear regression. The comparison of the removal efficiencies of pollutants using ANN model and experimental results showed that ANN modeling in competitive adsorption of phenolic compounds reasonably corroborated with the experimental results.     

Effect of different extracting solutions on the electrodialytic remediation of CCA-treated wood waste Part I. Behaviour of Cu and Cr

Removal of Cu and Cr from chromated copper arsenate (CCA)-treated wood waste under batch electrodialytic conditions was studied. The effect of different types of extracting solutions, such as deionised water or aqueous solutions of NaCl, formic acid, oxalic acid, and EDTA, on the magnitude and direction of the fluxes of Cu- and Cr-containing species in the electrodialytic cell was investigated. Oxalic acid was found to have the best performance if simultaneous removal of the two elements is required (removal efficiencies of 80.5% for Cu and 87.4% for Cr, respectively). A mixture of oxalic acid and formic acid also led to similar removal efficiencies. In these experiments, the target elements were accumulated in both the anode and cathode compartments of the electrodialytic cell due to the formation of negatively charged complexes with the organic acids used besides the free cationic forms. The latter were not present if EDTA was the extracting solution resulting in directing the Cu and Cr fluxes to the anode compartment. Contrary, these fluxes were exclusively to the cathode compartment if deionised water or an aqueous solution of NaCl were used. These extracting solutions proved suitable for solubilising (re-mobilisation) of Cu but were less efficient for Cr removal (less than 20% removal). Overall, the results obtained show the important role of the proper selection of the type and composition of the extracting solution for the success of subsequent electrodialytic removal of Cu and Cr from CCA-treated wood waste.     

Control of acid gases using a fluidized bed adsorber

During incineration, secondary pollutants such as acid gases, organic compounds, heavy metals and particulates are generated. Among these pollutants, the acid gases, including sulfur oxides (SO(x)) and hydrogen chloride (HCl), can cause corrosion of the incinerator piping and can generate acid rain after being emitted to the atmosphere. To address this problem, the present study used a novel combination of air pollution control devices (APCDs), composed of a fluidized bed adsorber integrated with a fabric filter. The major objective of the work is to demonstrate the performance of a fluidized bed adsorber for removal of acid gases from flue gas of an incinerator. The adsorbents added in the fluidized bed adsorber were mainly granular activated carbon (AC; with or without chemical treatment) and with calcium oxide used as an additive. The advantages of a fluidized bed reactor for high mass transfer and high gas-solid contact can enhance the removal of acid gases when using a dry method.On the other hand, because the fluidized bed can filter particles, fine particles prior to and after passing through the fluidized bed adsorber were investigated. The competing adsorption on activated carbon between different characteristics of pollutants was also given preliminary discussion. The results indicate that the removal efficiencies of the investigated acid gases, SO(2) and HCl, are higher than 94 and 87%, respectively. Thus, a fluidized bed adsorber integrated with a fabric filter has the potential to replace conventional APCDs, even when there are other pollutants at the same time.     

Adsorption of organic pollutants from coking and papermaking wastewaters by bottom ash

Bottom ash, a power plant waste, was used to remove the organic pollutants in coking wastewater and papermaking wastewater. Particular attention was paid on the effect of bottom ash particle size and dosage on the removal of chemical oxygen demand (COD). UV-vis spectra, fluorescence excitation-emission matrix (FEEM) spectra, Fourier transform infrared (FTIR) spectra, and scanning electron microscopic (SEM) photographs were investigated to characterize the wastewaters and bottom ash. The results show that the COD removal efficiencies increase with decreasing particle sizes of bottom ash, and the COD removal efficiency for coking wastewater is much higher than that for papermaking wastewater due to its high percentage of particle organic carbon (POC). Different trends of COD removal efficiency with bottom ash dosage are also observed for coking and papermaking wastewaters because of their various POC concentrations. Significant variations are observed in the FEEM spectra of wastewaters after treatment by bottom ash. New excitation-emission peaks are found in FEEM spectra, and the fluorescence intensities of the peaks decrease. A new transmittance band in the region of 1400-1420 cm(-1) is observed in FTIR spectra of bottom ash after adsorption. The SEM photographs reveal that the surface of bottom ash particles varies evidently after adsorption.     

Removal of 2,4-dichlorophenol and pentachlorophenol from waters by sorption using coal fly ash from a Portuguese thermal power plant

Chlorophenols are one of the most important groups of priority pollutants, due to their high toxicity, mutagenicity and carcinogenicity. Although activated carbon has been the preferred choice for the removal of such pollutants from wastewaters, the search for cheaper alternative sorbents became common in the last years. Fly ash, a by-product from coal burning power plants, has a surface composition that may enable the sorption of specific organic compounds. Therefore, this feasibility study presents the optimization of the operating parameters of a fixed-bed column containing fly ash particles, percolated by aqueous solutions of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) with concentrations of 1 and 100 microg/ml. Both chlorophenols were analysed by gas chromatography with electron capture detection (GC-ECD), after solid-phase microextraction (SPME), with limits of detection (LODs) of 7.28 microg/l for 2,4-DCP and 1.76 microg/l for PCP. Removal efficiencies above 99% were obtained for an initial concentration of 10 microg/ml of chlorophenols. Column saturation was achieved after 7h of continuous operation for 2,4-DCP and 10h for the PCP for feed levels of 10 microg/ml. Fly ash exhibited more affinity towards the sorption of PCP, in comparison to 2,4-DCP.     

Titania/carbon nanotube composite (TiO2/CNT) and its application for removal of organic pollutants

This review aimed to highlight recent development in the preparation of titania/carbon nanotube composite (TiO₂/CNT) and its application for the removal of organic pollutants in aqueous solution. Current studies indicate that the composite can enhance the absorption of visible light compared with pure TiO₂. Generally, synergistic effects were observed for the degradation of some dyes, phenols, and benzene derivatives. The role of CNTs in the composite was explained to function as a support material, concentrate organic pollutants on the composite surface and more importantly, to extend electron–hole (e–h) recombination time as electron scavenger. However, opposite effects were observed for the degradation of some pharmaceuticals (e.g., carbamazepine and diclofenac). Despite different mechanisms involved, most organic pollutants can be photocatalytically degraded within a few minutes or hours. The summarized results and raised issues in this review will attract more future research for this new photocatalyst, particularly in areas such as synthesis methods, degradation mechanisms, and performance for more diversified structures of organic compounds.     

Study of the degradation behaviour of dimethoate under microwave irradiation

In this work, the degradation of dimethoate under microwave irradiation assisted advanced oxidation processes (MW/oxidants) were studied. The efficiencies of the degradation of dimethoate in dilute aqueous solutions for a variety of oxidants with or without MW irradiation were compared. The results showed that the synergistic effects between MW and K(2)S(2)O(8) had high degradation efficiency for dimethoate. Simultaneously, UV/TiO(2)/K(2)S(2)O(8) photocatalytic oxidation degradation of dimethoate was investigated. The experimental results indicated that the method of microwave degradation of organic pollutants in the presence of oxidant could reduce reaction time and improve product yield. Microwave irradiation was an advisable choice for treating organic wastewaters and has a widely application perspective for non- or low-transparent and fuscous dye wastewaters.     

One-step processing of low-cost and superb natural magnetic adsorbent: kinetics and thermodynamics investigation for dye removal from textile wastewater

A simple, one-step and dry hybridization technique was successfully implemented to fabricate superb and low-cost magnetic adsorbent for removal of organic dyes. The structural and textural properties of the prepared banded iron formation @bentonite (BIF@BEN) composite were clearly investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS), Brunauer–Emmett–Teller surface area (BET) and porosity analysis (BJH) techniques. The dye removal efficiency was optimized by studying several parameters, namely, pH, temperature, contact time and initial dye concentration. The maximum adsorption capacity achieved for crystal violet (CV) and acid red (AR) dyes were about 117 and 91 mg/g, respectively at pH 7, 60 °C in 60 min. The equilibrium data of both dyes’ adsorption on the BIF@BEN composite showed better fitting to Langmuir isotherm. The thermodynamic studies revealed that the adsorption process is spontaneous, endothermic and favorable at high temperatures. The prepared magnetic adsorbent showed higher adsorption performance than activated bentonite for removal of anionic dye (AR) and the same performance for removal of cationic dye (CV). The magnetic adsorbent is actually reused and easily separated from textile wastewater with total removal efficiencies 81% and 74.5% for all inorganic and organic pollutants, respectively after two adsorption cycles.     

Amyloid Fibrils Aerogel for Sustainable Removal of Organic Contaminants from Water

Water contamination by organic pollutants is ubiquitous and hence a global concern due to detrimental effects on the environment and human health. Here, it is demonstrated that amyloid fibrils aerogels are ideal adsorbers for removing organic pollutants from water. To this end, amyloid fibrils prepared from β‑lactoglobulin, the major constituent of milk whey protein, are used as building blocks for the fabrication of the aerogels. The adsorption of Bentazone, Bisphenol A, and Ibuprofen, as model pollutants, is evaluated under quasi-static conditions, without use of energy or pressure. Through adsorption by amyloid fibrils aerogel, excellent removal efficiencies of 92%, 78%, and 98% are demonstrated for Bentazone, Bisphenol A, and Ibuprofen, respectively. Furthermore, the maximum adsorption capacity of amyloid fibrils aerogel for Bentazone, Bisphenol A, and Ibuprofen is 54.2, 50.6, and 69.6 mg g⁻¹, respectively. To shed light on the adsorption equilibrium process, adsorption isotherms, binding constants, saturation limits, and the effect of pH are evaluated. Finally, the regeneration of the aerogel over three consecutive cycles is studied, exhibiting high reusability with no significant changes in its removal performance. These results point at amyloid fibrils aerogels as a sustainable, efficient, and inexpensive technology for alleviating the ubiquitous water contamination by organic pollutants.     

A combined electrocoagulation-sorption process applied to mixed industrial wastewater

The removal of organic pollutants from a highly complex industrial wastewater by a aluminium electrocoagulation process coupled with biosorption was evaluated. Under optimal conditions of pH 8 and 45.45 Am(-2) current density, the electrochemical method yields a very effective reduction of all organic pollutants, this reduction was enhanced when the biosorption treatment was applied as a polishing step. Treatment reduced chemical oxygen demand (COD) by 84%, biochemical oxygen demand (BOD(5)) by 78%, color by 97%, turbidity by 98% and fecal coliforms by 99%. The chemical species formed in aqueous solution were determined. The initial and final pollutant levels in the wastewater were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the biosorbent was characterized with scanning electron microscopy (SEM) and energy dispersion spectra (EDS).