Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode

Electrochemical oxidation of polyethylene glycol (PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified(PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.     

Demulsification performance and mechanism of oil droplets by electrocoagulation: Role of surfactant

Surfactants are widely used to improve the solubility of oil in water in petrochemical, making it more difficult to remove oil–water emulsions during the water treatment process. Electrocoagulation (EC) is an appropriate method for treating oily wastewater and destabilizing emulsions. However, the demulsification mechanism of oil–water droplets emulsified by surfactants with different charges have not been investigated systematically. The demulsification performance of electrocoagulation on emulsions wastewater containing cationic, non-ionic, and anionic surfactants was studied. The results showed that the removal rate of total organic carbon (TOC) in oily wastewater with anionic surfactant by EC reached 92.98% ± 0.40% at a current density of 1 mA/cm², while that of the non-ionic surfactant was 84.88% ± 0.63%. The characterization of flocs showed that EC has the highest coagulation and demulsification of oil droplets with a negative charge on the surface (−70.50 ± 10.25 mV), which indicated that the charge neutralization of oil droplets was beneficial for the destabilization of the formed oily flocs. However, when the zeta potential of the oil droplets reached 75.50 ± 1.25 mV, the TOC removal efficiency was only 11.80% ± 1.43%. The TOC removal could achieve 33.23% ± 3.21% when the current density improved from 1 mA/cm² to 10 mA/cm². The enhanced removal was due to the sweep coagulation rather than charge neutralization. This study provides a fundamental basis for the electrochemical treatment of oily wastewater.     

Advanced treatment of dyeing wastewater towards reuse by the combined Fenton oxidation and membrane bioreactor process

The performance of combined Fenton oxidation and membrane bioreactor (MBR) process for the advanced treatment of an effluent from an integrated dyeing wastewater treatment plant was evaluated. The experimental results revealed that under the optimum Fenton oxidation conditions (initial pH 5, H 2 O 2 dosage 17 mmol/L, and Fe 2+ 1.7 mmol/L) the average total organic carbon (TOC) and color removal ratios were 39.3% and 69.5% after 35 min of reaction, respectively. Results from Zahn-Wallens Test also represented that Fenton process was effective to enhance the biodegradability of the test wastewater. As for the further purification of MBR process, TOC removal capacity was examined at different hydraulic retention times (HRT) of 10, 18 and 25 hr. Under the optimum HRT of 18 hr, the average TOC concentration and color of the final MBR effluent were 16.8 mg/L and 2 dilution time, respectively. The sludge yield coefficient was 0.13 g MLSS/g TOC and TOC degradation rate was 0.078 kg TOC/(m 3 ·day). The final effluent of MBR can meet the reuse criteria of urban recycling water-water quality standard for miscellaneous water consumption GBT18920-2002.     

Influence of moderate pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing activated carbon

A novel adsorbent based on iron oxide dispersed over activated carbon(AC) were prepared, and used for phosphate removal from aqueous solutions. The influence of pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing AC were determined. Two series of ACs, non-oxidized and oxidized carbon modified by iron(denoted as AC-Fe and AC/OFe), resulted in a maximum impregnated iron of 4.03% and 7.56%, respectively. AC/O-Fe showed 34.0%–46.6% higher phosphate removal efficiency than the AC-Fe did. This was first attributed to the moderate pre-oxidation of raw AC by nitric acid, achieved by dosing Fe(II) after a pre-oxidation, to obtain higher iron loading, which is favorable for phosphate adsorption. Additionally, the in-situ formed active site on the surface of carbon, which was derived from the oxidation of Fe(II) by nitric acid dominated the remarkably high efficiency with respect to the removal of phosphate. The activation energy for adsorption was calculated to be 10.53 and 18.88 kJ/mol for AC-Fe and AC/OFe, respectively. The results showed that the surface mass transfer and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.     

Preparation of Fe–Co based MOF-74 and its effective adsorption of arsenic from aqueous solution

To obtain a cost-effective adsorbent for the removal of arsenic in water,a novel nanostructured Fe–Co based metal organic framework(MOF-74)adsorbent was successfully prepared via a simple solvothermal method.The adsorption experiments showed that the optimal molar ratio of Fe/Co in the adsorbent was 2:1.The Fe_2Co_1MOF-74 was characterized by various techniques and the results showed that the nanoparticle diameter ranged from60 to 80 nm and the specific surface area was 147.82 m~2/g.The isotherm and kinetic parameters of arsenic removal on Fe_2Co_1MOF-74 were well-fitted by the Langmuir and pseudo-second-order models.The maximum adsorption capacities toward As(III)and As(V)were 266.52 and 292.29 mg/g,respectively.The presence of sulfate,carbonate and humic acid had no obvious effect on arsenic adsorption.However,coexisting phosphate significantly hindered the removal of arsenic,especially at high concentrations(10 mmol/L).Electrostatic interaction and hydroxyl and metal–oxygen groups played important roles in the adsorption of arsenic.Furthermore,the prepared adsorbent had stable adsorption ability after regeneration and when used in a real-water matrix.The excellent adsorption performance of Fe_2Co_1MOF-74 material makes it a potentially promising adsorbent for the removal of arsenic.     

Advanced treatment of wet-spun acrylic fiber manufacturing wastewater using three-dimensional electrochemical oxidation

A three-dimensional electrochemical oxidation(3D-EC) reactor with introduction of activated carbon(AC) as particle micro-electrodes was applied for the advanced treatment of secondary wastewater effluent of a wet-spun acrylic fiber manufacturing plant. Under the optimized conditions(current density of 500 A/m~2, circulation rate of 5 mL/min, AC dosage of 50 g, and chloride concentration of 1.0 g/L), the average removal efficiencies of chemical oxygen demand(COD_(cr)), NH3–N, total organic carbon(TOC), and ultraviolet absorption at 254 nm(UV_(254)) of the 3D-EC reactor were 64.5%, 60.8%, 46.4%, and 64.8%, respectively; while the corresponding effluent concentrations of COD_(cr), NH_3–N, TOC, and UV_(254) were 76.6, 20.1, and42.5 mg/L, and 0.08 Abs/cm, respectively. The effluent concentration of COD_(cr) was less than 100 mg/L, which showed that the treated wastewater satisfied the demand of the integrated wastewater discharge standard(GB 8978-1996). The 3D-EC process remarkably improved the treatment efficiencies with synergistic effects for COD_(cr), NH_3–N, TOC, and UV_(254) during the stable stage of 44.5%, 38.8%, 27.2%, and 10.9%, respectively, as compared with the sum of the efficiencies of a two-dimensional electrochemical oxidation(2D-EC) reactor and an AC adsorption process, which was ascribed to the numerous micro-electrodes of AC in the 3D-EC reactor. Gas chromatography mass spectrometry(GC–MS) analysis revealed that electrochemical treatment did not generate more toxic organics, and it was proved that the increase in acute biotoxicity was caused primarily by the production of free chlorine.     

Spectroscopic study on transformations of dissolved organic matter in coal-to-liquids wastewater under integrated chemical oxidation and biological treatment process

A large amount of wastewater containing various toxic organic contaminants is produced during coal-to-liquids process. In this study, several spectroscopic methods were used to monitor the transformation of organic pollutants during an integrated chemical oxidation and biological process. The results showed that the hydrophobic acid fraction increased after Fenton oxidation, which was likely due to the production of small-molecule organic acids. Soluble microbial products were generated during biological treatment processes,which were degraded after ozonation; meanwhile, the hydrophilic base and acid components increased. Ultraviolet-visible spectroscopic analysis indicated that peaks at the absorption wavelengths of 280 and 254 nm, which are associated with aromatic substances, were detected in the raw water. The aromatic substances were gradually removed, becoming undetectable after biological aeration filter(BAF) treatment. Fourier transform infrared spectroscopy analysis revealed that the functional groups of phenols;benzene, toluene, ethylbenzene, and xylene(BTEX); aromatic hydrocarbons; aliphatic acids;aldehydes; and esters were present in raw wastewater. The organic substances were oxidized into small molecules after Fenton treatment. Aromatic hydrocarbons were effectively removed through bioadsorption and biodegradation after BAF process.Biodegradable organic matter was reduced and finally became undetectable after anoxic–oxic treatment in combination with a membrane bioreactor. Four fluorescent components were fractionated and obtained via excitation–emission matrix parallel factor analysis(EEM-PARAFAC). Dissolved organic matter fractionation in conjunction with EEM-PARAFAC was able to monitor more precisely the evolution of characteristic organic contaminants.     

Efficient treatment of azo dye containing wastewater in a hybrid acidogenic bioreactor stimulated by biocatalyzed electrolysis

In this study, a novel scaled-up hybrid acidogenic bioreactor(HAB) was designed and adopted to evaluate the performance of azo dye(acid red G, ARG) containing wastewater treatment. Principally, HAB is an acidogenic bioreactor coupled with a biocatalyzed electrolysis module. The effects of hydraulic retention time(HRT) and ARG loading rate on the performance of HAB were investigated. In addition, the influent was switched from synthetic wastewater to domestic wastewater to examine the key parameters for the application of HAB. The results showed that the introduction of the biocatalyzed electrolysis module could enhance anoxic decolorization and COD(chemical oxygen demand) removal. The combined process of HAB-CASS presented superior performance compared to a control system without biocatalyzed electrolysis(AB-CASS). When the influent was switched to domestic wastewater, with an environment having more balanced nutrients and diverse organic matters, the ARG, COD and nitrogen removal efficiencies of HAB-CASS were further improved, reaching 73.3% ± 2.5%, 86.2% ± 3.8% and 93.5% ± 1.6% at HRT of 6 hr, respectively, which were much higher than those of AB-CASS(61.1% ± 4.7%,75.4% ± 5.0% and 82.1% ± 2.1%, respectively). Moreover, larger TCV/TV(total cathode volume/total volume) for HAB led to higher current and ARG removal. The ARG removal efficiency and current at TCV/TV of 0.15 were 39.2% ± 3.7% and 28.30 ± 1.48 m A,respectively. They were significantly increased to 62.1% ± 2.0% and 34.55 ± 0.83 m A at TCV/TV of 0.25. These results show that HAB system could be used to effectively treat real wastewater.     

Nitrification characteristics of nitrobacteria immobilized in waterborne polyurethane in wastewater of corn-based ethanol fuel production

A technology to achieve stable and high ammonia nitrogen removal rates for corn distillery wastewater (ethanol fuel production) treatment has been designed. The characteristics of nitrifying bacteria entrapped in a waterborne polyurethane (WPU) gel carrier were evaluated after acclimation. In the acclimation period, nitrification rates of WPU-immobilized nitrobacteria were monitored and polymerase chain reaction (PCR) was also carried out to investigate the change in ammonium-oxidizing bacteria. The results showed that the pellet nitrification rates increased from 21 to 228 mg-N/(L-pellet. hr) and the quantity of the ammonia oxidation bacteria increased substantially during the acclimation. A continuous ammonia removal experiment with the anaerobic pond effluent of a distillery wastewater system was conducted with immobilized nitrifying bacteria for 30 days using an 80 L airlift reactor with pellets at a fill ratio of 15% (V/V). Under the conditions of 75 mg/L influent ammonia, hydraulic retention time (HRT) of 3.7--5.6 hr, and dissolved oxygen (DO) of 4 mg/L, the effluent ammonia concentration was lower than 10 mg/L and the ammonia removal efficiency was 90%. While the highest ammonia removal rate, 162 mg-N/(L-pellet.hr), was observed when the HRT was 1.3 hr.     

Treatment of desizing wastewater from the textile industry by wet air oxidation

This paper describes the application of wet air oxidation to the treatment of desizing wastewater from two textile companies. A two-liter high temperature, high pressure autoclave reactor was used in the study. The range of operating temperatures examined was between 150 and 290℃, and the partial pressure of oxygen ranged from 0. 375 to 2.25 MPa. Variations in pH,CODCr and TOD content were monitored during each experiment and used to assess the extent of conversion of the process. The effects of temperature, pressure and reaction time were explored extensively. More than 90 ％ CODCr reduction and 80 ％ TOC removal have been obtained. The results have also been demonstrated that WAO is a suitable pre-treatment methods due to improvement of the BOD5/CODCr ratio of desizing wastewater. The reaction kinetics of wet air oxidation of desizing wastewater has been proved to be two steps, a fast reaction followed by a slow reaction stage.     

Formic acid as an alternative reducing agent for the catalytic nitrate reduction in aqueous media

Formic acid was used for the nitrate reduction as a reductant in the presence of Pd:Cu/γ-alumina catalysts. The surface characteristics of the bimetallic catalyst synthesized by wet impregnation were investigated by SEM, TEM-EDS. The metals were not distributed homogeneously on the surface of catalyst, although the total contents of both metals in particles agreed well with the theoretical values. Formic acid decomposition on the catalyst surface, its influence on solution pH and nitrate removal efficacy was investigated. The best removal of nitrate (50 ppm) was obtained under the condition of 0.75 g/L catalyst with Pd:Cu ratio (4:1) and two fold excess of formic acid. Formic acid decay patterns resembled those of nitrate removal, showing a linear relationship between kf (formic acid decay) and k (nitrate removal). Negligible amount of ammonia was detected, and no nitrite was detected, possibly due to buffering effect of bicarbonate that is in situ produced by the decomposition of formic acid, and due to the sustained release of H2 gas.     

Bioaugmentation with a pyridine-degrading bacterium in a membrane bioreactor treating pharmaceutical wastewater

The bacterial strain Paracoccus denitrificans W12, which could utilize pyridine as its sole source of carbon and nitrogen, was added into a membrane bioreactor （MBR） to enhance the treatment of a pharmaceutical wastewater. The treatment efliciencies investigated showed that the removal of chemical oxygen demand, total nitrogen, and total phosphorus were similar between bioaugmented and non-bioaugmented MBRs, however, significant removal of pyridine was obtained in the bioaugmented reactor. When the hydraulic retention time was 60 hr and the influent concentration of pyridine was 250-500 mg/L, the mean effluent concentration of pyridine without adding W12 was 57.2 mg/L, while the pyridine was degraded to an average of 10.2 mg/L with addition of W12. The bacterial community structure of activated sludge during the bioaugmented treatment was analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE）. The results showed that the W12 inoculum reversed the decline of microbial community diversity, however, the similarity between bacterial community structure of the original sludge and that of the sludge after bioaugmentation decreased steadily during the wastewater treatment. Sequencing of the DNA recovered from DGGE gel indicated that sp., Sphingobium sp., Comamonas sp., and Hyphomicrobium sp. were the dominant organisms in time sequence in the bacterial community in the bioaugmented MBR. This implied that the bioaugmentation was affected by the adjustment of whole bacterial community structure in the inhospitable environment, rather than being due solely to the degradation performance of the bacterium added.     

Dyes wastewater treatment by reduction-oxidation process in an electrochemical reactor packed with natural manganese mineral

A novel technology which combined electrochemical process catalyzed by manganese mineral with electro-assisted coagulation process was proposed in this study. The mineralization of organic pollutant from simulated dye wastewater containing an azo dye Acid Red B（ARB） was experimentally investigated using this method. It was found that the manganese mineral could catalyze the electrochemical process dramatically. The TOC removal percentage of electrochemical treatment catalyzed by manganese mineral was 43.6% while the TOC removal percentage of the process using the manganese mineral alone and using the electrolysis alone were 9.3% and 20.8%, respectively. Moreover, it was found that combined electroxidation with electro-assisted coagulation process could more effectively eliminate ARB. After a period of 180 min electrooxidation and 300 min electroreduction, almost 66.9% of TOC was removed, and the dissolved Mn^2＋. could be effectivly removed. The effects of the order of oxidation and reduction, the proper ratio electrooxidation/reduction time, and current density on the removal efficiency were investigated in detail. In addition, a proposed mechanism of manganese-mineral-catalyzed electrooxidation-reduction process was discussed in this paper.     

Hg0 removal from flue gas over different zeolites modified by FeCl3

The elemental mercury removal abilities of three different zeolites(Na A, Na X, HZSM-5)impregnated with iron(Ⅲ) chloride were studied on a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy, and temperature programmed desorption(TPD) analyses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg0, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury(Hg0)into oxidized mercury(Hg2+). The crystallization of Na Cl due to the ion exchange effect during the impregnation of Na A and Na X reduced the number of active Cl species on the surface, and restricted the physisorption of Hg0. Therefore, the Hg0 removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of Fe Cl3–HZSM-5 was mainly in the form of mercuric chloride(Hg Cl2), while on Fe Cl3–Na X and Fe Cl3–Na A it was mainly mercuric oxide(Hg O).     

Phosphate removal from domestic wastewater using thermally modified steel slag

This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed(35.5 kg) removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca–P forms accounted for 81.4%–91.1%, i.e., Ca10–P 50.6%–65.1%, Ca8–P 17.8%–25.0%,and Ca2–P 4.66%–9.20%. The forms of Al–P, Fe–P, and O–P accounted for only 8.9%–18.6%. The formation of Ca10–P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.     

Revealing the effect of preparation parameters on zeolite adsorption performance for low and medium concentrations of ammonium

The effect of preparation parameters on the performance of zeolite for ammonium(20–300 mg N/L) adsorption from simulated wastewater is reported. It was found that the ratios of Na_2O/SiO_2 and Si/Al had a more important influence than crystallization time on zeolite adsorption properties. Relatively low Na_2O/SiO_2 ratios were beneficial for fabrication of zeolites with high proportions of micropore area and volume, which led to the surface adsorption mechanism being dominated by surface free energy and pore effects. However,with decreasing Si/Al ratios, the effect of ion-exchange was more prominent due to the high negative surface potential of zeolite. In addition, the concentration of weak acid sites on the zeolites was increased with lower ratios of Na_2O/SiO_2 and Si/Al, which may promote ammonium removal. Therefore, the most effective zeolite for ammonium removal, which was fabricated at Na_2O/SiO_2= 1.375, Si/Al = 4 and crystallization time of 48 hr, exhibited the cooperative effects of adsorption, ion-exchange and a large amount of weak acid sites. The maximum ammonium adsorption capacity(35.06 ± 0.98 mg/g) and the removal efficiency(94.44% ± 4.00%) were obtained at the dosage of 4.0 g/L zeolite NaX at ammonium concentrations of 300 mg N/L and 20 mg N/L, respectively. The Freundlich isotherm and pseudo-first-order kinetics models provided excellent fitting for the ammonium adsorption process. In addition, zeolite NaX showed about 1.23–3.2 times the ammonium adsorption capacity of clinoptilolite. The stable and efficient reusability of zeolite NaX after five regeneration cycles demonstrated that this adsorbent has considerable potential for practical industrial applications.     

Drinking water treatment using a submerged internal-circulation membrane coagulation reactor coupled with permanganate oxidation

A submerged internal circulating membrane coagulation reactor(MCR) was used to treat surface water to produce drinking water. Polyaluminum chloride(PACl) was used as coagulant,and a hydrophilic polyvinylidene fluoride(PVDF) submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure(TMP), zeta potential(ZP) of the suspended particles in raw water, and KMnO_4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China(GB 5749-2006), as evaluated by turbidity(1 NTU) and total organic carbon(TOC)(5 mg/L)measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon(DOC) in the raw water also increased with increasing TMP in the range of 0.01–0.05 MPa. High ZP induced by PACl, such as 5–9 mV, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity.However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1–2 mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO_4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes.     

Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar

Shortage in phosphorus(P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar(Ca–Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca–Mg/biochar was rich in organic functional groups and in Ca O and Mg O nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca–Mg/biochar could be accelerated by nano-Ca O and nano-Mg O particles and reached equilibrium after 360 min.The process was endothermic, spontaneous, and showed an increase in the disorder of the solid–liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63 mg/g. The P adsorption selectivity of Ca–Mg/biochar could not be significantly influenced by the typical p H level of biogas fermentation liquid. The nano-Ca O and nano-Mg O particles of Ca–Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca–Mg/biochar were in the order of Ca–Mg/B600 Ca–Mg/B450 Ca–Mg/B300. Results revealed that postsorption Ca–Mg/biochar can continually release P and is more suitable for an acid environment.     

Synthesis of zinc-carboxylate metal-organic frameworks for the removal of emerging drug contaminant (amodiaquine) from aqueous solution

We herein report the removal of amodiaquine, an emerging drug contaminant from aqueous solution using [Zn2(fum)2(bpy)] and [Zn4 O(bdc)3](fum = fumaric acid; bpy =4,4-bipyridine; bdc = benzene-1,4-dicarboxylate) metal–organic frameworks(MOFs) as adsorbents. The adsorbents were characterized by elemental analysis, Fourier transform infrared(FT-IR) spectroscopy, and powder X-ray diffraction(PXRD). Adsorption process for both adsorbents were found to follow the pseudo-first-order kinetics, and the adsorption equilibrium data fitted best into the Freundlich isotherm with the R~2 values of 0.973 and0.993 obtained for [Zn_2(fum)_2(bpy)] and [Zn_4 O(bdc)_3] respectively. The maximum adsorption capacities foramodiaquine in this study were found to be 0.478 and 47.62 mg/g on the[Zn_2(fum)_2(bpy)] and [Zn_4 O(bdc)_3] MOFs respectively, and were obtained at p H of 4.3 for both adsorbents. FT-IR spectroscopy analysis of the MOFs after the adsorption process showed the presence of the drug. The results of the study showed that the prepared MOFs could be used for the removal of amodiaquine from wastewater.     

Treatment of 2-phenylamino-3-methyl-6-di-n-butylaminofluoran production effluent by combination of biological treatments and Fenton’s oxidation

High strength refractory organic stream is produced during the production of 2-phenylamino-3-methyl-6-di-n-butylaminofluoran (One Dye Black 2,abbr.ODB 2),a novel heat-sensitive material with a promising market.In this study,a combination of acidification- precipitation,primary biological treatment,Fenton's oxidation and another biological treatment was successfully used for the removal of COD from 18000-25000 mg/L to below 200 mg/L from the ODB 2 production wastewater in a pilot experiment.A COD removal of 70%-80% was achieved by acidification-precipitation under a pH of 2.5-3.0.The first step biodegradation permitted an average COD removal of 70% under an hydraulic residence time (HRT) of 30 h.By batch tests,the optimum conditions of Fenton's oxidation were acquired as:Fe~(2 ) dose 6.0 mmol/L;H_2O_2 dose 3000 mg/L;and reaction time 6 h.The second step biological treatment could ensure an effluent COD below 200 mg/L under an HRT of 10 h following the Fenton's treatment.