水铁矿及其腐殖酸复合体对Sb(Ⅴ)的吸附行为研究

在实验室条件下制备了水铁矿和水铁矿与腐殖酸复合物,通过X射线衍射、傅里叶红外光谱、Zeta电位及比表面积的测定对其基本性质进行了表征,并采用静态批处理吸附试验研究了水铁矿及其腐殖酸复合物对Sb(Ⅴ)的吸附行为特征,探讨了吸附时间、初始pH值、初始浓度、不同干扰离子(PO_4~(3-)、CO_3~(2-)、NO~-_3和Cl~-)对水铁矿及其复合物吸附Sb(Ⅴ)的影响.结果表明:腐殖酸与水铁矿结合后未改变水铁矿的晶型结构,但降低了水铁矿的零电点与比表面积.水铁矿及其复合物对Sb(Ⅴ)的吸附过程符合Langmuir和伪二级动力学模型,腐殖酸的加入抑制了水铁矿对Sb(Ⅴ)的吸附.随着pH的上升,水铁矿与复合物的去质子化能力增强,对Sb(Ⅴ)的吸附量减小;溶液中共存离子PO_4~(3-)、CO_3~(2-)对水铁矿及其腐殖酸复合物吸附Sb(Ⅴ)有较强的抑制作用.     

磁性CeO2-Fe3O4复合材料光催化/吸附去除水中As(III)

原水砷污染问题严重威胁饮用水水质安全,随着生活饮用水标准的提高,致使多地饮用水中砷超标问题突显.本研究利用CeO₂半导体的光催化活性及CeO₂和Fe₃O₄对As（V）的强亲和力,合成了双组份磁性CeO₂-Fe₃O₄复合材料,并采用SEM、XRD、BET和VSM等手段进行表征,考察复合材料的光催化/吸附除砷效果;研究了初始pH值、共存离子等因素对吸附除砷效果的影响;采用等温吸附模型、吸附动力学模型等手段进行吸附特性研究.实验结果表明,在光催化过程中,·OH和·O₂^-为主要的活性氧化物种.在紫外照射下,As（Ⅲ）能完全被氧化为毒性较低的As（V）,同时将As（V）高效吸附于CeO₂-Fe₃O₄粒子表面.在中性条件下,CeO₂-Fe₃O₄粒子对砷的饱和吸附量为122.19 mg·g^-1.共存离子Cl^-和SO₄^2-对As（V）的吸附没有显著影响,而CO₃^2-、SiO₃^2-和PO₄^3-与As（V）存在明显的竞争吸附,使As（V）的吸附去除效果明显降低.吸附动力学和吸附等温线模拟分别符合准二级动力学方程和Freundlich吸附等温线,表明As（V）的吸附以化学吸附为主导.CeO₂-Fe₃O₄复合吸附剂可快速实现固液分离,容易再生且重复利用性较好,具有广泛的应用前景.     

镧铁羟基氧化物修饰还原氧化石墨烯复合电极材料电吸附除磷效能及机理研究

污水处理厂尾水中低浓度PO₄^3-的排放是水体中总磷的主要来源,是导致水体富营养化的重要原因之一,对其开展深度去除的应用基础性研究具有重要的理论意义和实践价值.复合金属氧化物材料表现出较好PO₄^3-吸附能力,但仍然存在吸附速率较慢的问题.本研究采用溶剂热、复合薄膜压片法制备了镧铁羟基氧化物（LaFeO_xH_y）修饰还原氧化石墨烯（rGO）复合电极材料（LaFe-rGO）,LaFe-rGO复合电极材料显著提高了对PO₄^3-的吸附速率,5 min可达到吸附平衡,在1.2 V电压下对PO₄^3-的最大吸附量为108.69 mg·g^-1.提出了基于晶格氧提供活性位点及LaFe-rGO双电层电容电促吸附除磷机理,LaFe-rGO复合电极材料中晶格氧La-O与Fe-O同时对PO₄^3-吸附提供吸附位点,PO₄^3-与材料中的La/Fe键合以形成内球表面复合物La/Fe-PO₄,掺杂在rGO表面上的LaFeO_xH_y增加了电极材料电容并提高了其电化学活性,促进了LaFe-rGO复合电极材料对PO₄^3-的吸附.     

不同水化学因素对砷在河砂上的吸附影响研究

河岸带作为一种常见的地下水和地表水相互作用带,砷在其主要含水层介质中的行为特征及其影响因素较少有研究报道.基于此,采集河岸带河砂开展室内实验,查明砷在河砂上的吸附动力学和等温吸附特征,重点探究不同pH、氧化还原条件和共存离子对砷与河砂相互作用的影响.结果发现：As（Ⅲ）和As（V）在河砂上的吸附过程符合准二级动力学模型,均能很好地用Langmuir和Freundlich模型拟合（R²>0.99）;随着pH值（3~11）的增大,河砂对As（Ⅲ）和As（V）的平衡吸附量（q_e）逐渐减小;相对于有氧环境,缺氧环境下q_e较低且随着初始S^2-含量的增加而逐渐减小;整体上,共存阴离子对河砂吸附砷存在抑制作用,顺序为：PO₄^3- > SiO₃^2- > S^2->HCO₃^- > SO₄^2- > NO₃^-,共存阳离子对河砂吸附砷具有促进作用,顺序为：Fe³⁺>Fe²⁺.     

PO43-协同钴介体电催化体系用于亚甲基蓝(MB)的降解性能研究

以阳离子型染料亚甲基蓝（MB）废水为研究对象,采用钴介体电催化（MEO/Co（Ⅱ））与PO₄^3-协同作用体系（简称PO₄^3--MEO/Co（Ⅱ）体系）,进行MB电催化降解实验,研究Co²⁺浓度、电流密度、pH值、电解质浓度等因素对PO₄^3--MEO/Co（Ⅱ）体系电催化降解MB的效果,并对其分解产物及机理进行了分析与探讨.结果表明：①PO₄^3--MEO/Co（Ⅱ）体系主要的氧化性中间产物为Co³⁺,同时存在少量羟基自由基及过磷酸盐.②PO₄^3-与MEO/Co（Ⅱ）体系之间具有明显的协同催化作用.PO₄^3--MEO/Co（Ⅱ）体系在40 min内对MB的降解率高达100%,是钴介电体系降解率的1.2倍,直接电化学氧化体系降解率的5倍.③Co²⁺浓度、电流密度及pH值对PO₄^3--MEO/Co（Ⅱ）体系氧化性能影响较大,而PO₄^3-浓度、电解质浓度对PO₄^3--MEO/Co（Ⅱ）体系的氧化性能影响较小.④PO₄^3--MEO/Co（Ⅱ）体系对MB的降解过程为：先从MB分子的N—C连接处断键,形成吩噻嗪、2-氨基-5-（N-甲基甲酰胺）苯磺酸及N¹,N¹-二甲基-1,4二氨苯等物质;然后将其降解为苯胺、苯酚、苯磺酸等;最终分解成CO₂和水等无机物.⑤PO₄^3--MEO/Co（Ⅱ）体系对MB的降解机理为：通过铂钛电极直接电催化,以及Co³⁺、过磷酸根、羟基自由基的间接氧化,其中,起主导作用的是Co³⁺的电催化氧化.     

纳米CuO在水体环境中的转化行为及其对大型溞的毒性效应

为探究纳米CuO颗粒（CuO NP）在水体中的环境暴露风险,考察了腐殖酸（SRHA）和酸根离子对CuO NP转化行为的影响,探讨了CuO NP在不同条件下转化对大型溞的毒性效应差异.结果表明,与单独水体中CuO NP的转化行为相比,H₂PO₄^-显著促进了CuO NP释放Cu²⁺,Cl^-、NO₃^-、SO₄^2-对CuO NP的转化行为没有显著影响,而CO₃^2-、HCO₃^-、PO₄^3-、HPO₄^2-抑制了CuO NP中Cu²⁺的释放;SRHA显著促进了CuO NP释放Cu²⁺,但HCO₃^-、PO₄^3-的存在可以明显抑制SRHA促进CuO NP中Cu²⁺释放的进程.CuO NP在单独水体中,以及在Cl^-、PO₄^3-和SRHA+PO₄^3-存在的水体中转化后对大型溞的致死中浓度为16~32 mg·L^-1,而在SRHA与SRHA+Cl^-存在的水体中转化后对大型溞的致死中浓度分别降到0.8和2.5 mg·L^-1,说明SRHA促进了CuO NP释放Cu²⁺,提高了CuO NP颗粒分散性,使其易于被大型溞体内细胞组织摄取,增加了CuO NP对大型溞的毒性效应,因此,环境转化对CuO NP的环境暴露风险有重要影响.     

改性活性炭除亚砷酸盐的性能研究

制备了2种负载铁锰氧化物的改性活性炭（FM-GAC-1、FM-GAC-2）并研究其对水中的亚砷酸盐的去除性能.考察了2种改性活性炭除三价砷的吸附等温线、反应动力学及pH、温度、水中共存离子对其去除三价砷的影响,发现FM-GAC-1和FM-GAC-2对三价砷均有较好的去除效果,吸附容量分别为32.37、 26.67 mg·g^-1.吸附速率符合拟二级反应动力学,化学反应控制过程是改性活性炭除砷的限速步骤.pH值偏酸性有利于吸附的进行,温度升高,吸附容量有所下降,该吸附过程是自发的放热过程.同时,水体中的共存阴离子在其浓度值为三价砷的200倍时,SiO^2-₃、 PO^2-₃、NO^-₃对FM-GAC-1吸附三价砷有明显影响; SiO^2-₃、CO^2-₃对FM-GAC-2吸附三价砷有显著影响.总体上讲,FM-GAC-1较FM-GAC-2有更为优异的去除三价砷性能.     

荞麦皮生物炭对奥硝唑的吸附研究

以农林废弃物荞麦皮为原料制备生物炭（BBC）,采用XRD、Raman、N₂吸附/脱附、FTIR和XPS方法对BBC进行表征,研究其对奥硝唑（Ornidazole,ONZ）的吸附性能及机理.结果表明,热解温度在400~800 ℃, BBC的得炭率为24.5%~34%;温度升高,BBC的芳香性和稳定性增加（H/C由0.047降低至0.013）,比表面积和孔容升高,对ONZ的吸附率增加.采用不同动力学和吸附等温线模型对不同热解温度BBC吸附ONZ的过程进行模拟,吸附过程符合准二级动力学模型和Langmuir吸附等温线模型,表明BBC对ONZ的吸附为单层吸附.其中热解温度为800 ℃时的BBC（BBC-800）对ONZ的吸附效果最好,最大吸附量达到27.12 mg?g^-1.初始pH为3.02~11.03,对BBC-800吸附ONZ的影响不大;共存离子（Na⁺、NH₄⁺、CO₃^2-、HCO₃^-和SO₄^2-）对吸附过程有一定促进作用; 腐殖酸（HA）抑制吸附效果, 5.0 g?L^-1时ONZ的吸附率由97.15%下降至56.86%. FTIR、N₂吸附/脱附和XPS分析结果表明, BBC-800对ONZ的吸附机制主要包括孔隙扩散,生物炭表面与ONZ分子间的氢键、π-π和p-π共轭作用. BBC-800能够有效去除实际水体（污水厂二沉池出水、湖水）中ONZ的残留. 吸附-解吸3次循环实验表明,BBC-800仍具有较好的吸附性能, 对ONZ的吸附容量为14.10 mg?g^-1. 研究结果对荞麦皮的资源化及奥硝唑类药物的有效去除具有重要参考价值.     

Antimony(V) removal from water by iron-zirconium bimetal oxide: Performance and mechanism

A Fe-Zr binary oxide adsorbent has been successfully synthesized using a co-precipitation method. It showed a better performance for antimonate (Sb(V)) removal than zirconium oxide or amorphous ferric oxide. The experimental results showed that the Fe-Zr adsorbent has a capacity of 51 mg/g at an initial Sb(V) concentration of 10 mg/L at pH 7.0. Sb(V) adsorption on the Fe-Zr bimetal oxide is normally an endothermic reaction. Most of the Sb(V) adsorption took place within 3 hr and followed a pseudo second-order rate law. Co-existing anions such as SO₄^2-, NO₃^- and Cl^- had no considerable effects on the Sb(V) removal; PO₃^4- had an inhibitory effect to some extent at high concentration; while CO_₃^2- and SiO₄^4- showed significant inhibitory effects when they existed in high concentrations. The mechanism of Sb(V) adsorption on the adsorbent was investigated using a combination of zeta potential measurements, XPS, Raman, FT-IR observations and SO₄^2- release determination. The ionic strength dependence and zeta potential measurements indicated that inner-sphere surface complexes were formed after Sb(V) adsorption. Raman and XPS observations demonstrated that both Fe-OH and Zr-OH sites at the surface of the Fe-Zr adsorbent play important roles in the Sb(V) adsorption. FT-IR characterization and SO₄^2- release determination further demonstrated that the exchange of SO₄^2- with Sb(V) also could promote the adsorption process. In conclusion, this adsorbent showed high potential for future application in Sb(V) removal from contaminated water.     

低磷污水的HAP诱导结晶磷回收

为考察羟基磷酸钙（HAP）诱导结晶对低磷污水中PO₄^3--P的回收效果,以污水厂尾水为研究对象,采用方解石为晶种,首先全面对比了HAP诱导结晶与均相结晶的PO₄^3--P去除效果,然后通过改变晶种粒径和投加量,研究了晶种对PO₄^3--P回收的影响,并探讨了结晶反应条件对PO₄^3--P回收和产物晶型的影响.结果表明：HAP诱导结晶除磷效果要优于均相结晶,当结晶体系pH不超过9.0且残余Ca²⁺为100 mg·L^-1时,前者可将PO₄^3--P浓度降至0.5 mg·L^-1左右,后者则为5.0 mg·L^-1左右.构晶离子的扩散过程是HAP诱导结晶的控速步骤,减小晶种粒径和增加晶种投加量有利于构晶离子的扩散,可提高结晶反应速率,进而提高HAP诱导结晶对低磷污水的适应性,使PO₄^3--P回收率得到提高.对PO₄^3--P浓度为1.0 mg·L^-1的模拟废水,晶种投加量为10 g·L^-1、粒径为45 μm、Ca²⁺投加量为50 mg·L^-1和pH=9时,在10 min的反应时间内HAP诱导结晶可获得80%以上的PO₄^3--P回收率,出水PO₄^3--P和pH满足GB 3838—2002的Ⅱ类标准（0.1 mg·L^-1）.实验条件下,HAP诱导结晶产物晶型主要为HAP及其前驱物无定形态羟基磷酸钙（ACP）,产物结晶度随着pH的提高和晶种粒径的减小而提高.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.