Immobilization of microorganisms using carrageenan gels coated with chitosan and application to biodegradation of 4-chlorophenol

A new cell immobilization method based on the replacement of KCl by KCl+chitosan as the gelling agent was developed. The experimental results showed that through addition of chitosan into gelling agent, the mechanical strength and the thermal stability of the carrageenan gel were greatly improved. The new immobilization method was used to entrap a chlorophenol degrading microorganism. The immobilized microbial cells were applied for chlorophenol biodegradation. The experiments demonstrated that immobilized cells exhibit a higher bioactivity in the degradation of chlorophenol than free cells.

Effect of Sb dopant amount on the structure and electrocatalytic capability of Ti/Sb-SnO_2 electrodes in the oxidation of 4-chlorophenol

Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The physicochemical properties of the Sb-SnO2 coating were markedly influenced by different amounts of Sb dopant. The electrodes, which contained 5% Sb dopant in the coating, presented a much more homogenous surface and much smaller mud-cracks, compared with Ti/Sb-SnO2 electrodes containing 10% or 15% Sb dopant, which exibited larger mud cracks and pores on the surface. However, the main microstructure remained unchanged with the addition of the Sb dopant. No new crystal phase was observed by X-ray diffraction （XRD）. The electrochemical oxidation of 4-chlorophenol on the Ti/SnO2 electrode with 5% Sb dopant was inclined to electrochemical combustion; while for those containing more Sb dopant, intermediate species were accumulated. The electrodes with 5% Sb dopant showed the highest efficiency in the bulk electrolysis of 4-chlorophenol at a current density of 20 mA/cm^2 for 180 min; and the removal rates of 4-chlorophenol and COD were 51.0% and 48.9%, respectively.

Biodegradation of 4-Chlorophenol by Candida albicans PDY-07 under Anaerobic Conditions

Candida albicans PDY-07 was isolated from activated sludge under anaerobic conditions and identified as a member belonging to the genus Candida. Pure culture of C. albicans PDY-07, biodegradation of 4-chlorophenol (4-CP) was carried out under anaerobic conditions in Erlenmeyer flasks at 35°C, with an initial pH of 7.0–7.2 and a starting inoculum of 10%(by volume). The results showed that, under the above-mentioned conditions, C. albicans PDY-07 could thoroughly biodegrade 4-CP up to a concentration of 300mg·L?1 within 244h and that it had a high tolerance potential of up to 440mg·L?1 for 4-CP. With the increase in the initial concentrations of 4-CP, substrate inhibition was obviously enhanced. There was increased consumption of 4-CP, which was not assimilated by the cell for growth but was used to counteract the strong substrate inhibition. In addition, the cell growth and substrate-degradation kinetics of 4-CP as the sole source of carbon and energy for the strain in batch cultures were also investigated over a wide range of substrate concentrations (2.2–350mg·L?1), using the proposed cell growth and degradation kinetic models. The results recorded from these experiments showed that the proposed kinetic models adequately described the dynamic behavior of 4-CP biodegradation by C. albicans PDY-07.

Oxidative Degradation of 4-chlorophenol in Aqueous Induced by Plasma with Submersed Glow Discharge Electrolysis

The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined by high performance liquid chromatography （HPLC）. Various influencing factors such as the initial pH, the concentration of 4-CP and the catalytic action of Fe^2＋ were examined. The results indicate that 4-CP is eventually degraded into inorganic ion, dioxide carbon and water. The attack of hydroxyl radicals on the benzene rings of 4-CP in the initial stage of oxidative reactions is presumed to be a key step. They also suggest that the reaction is of a pseudo-first order kinetic reaction and the proposed method is an efficient way for the 4-CP degradation,

Biodegradation of 4-Chlorophenol by Candida albicans PDY-07 under Anaerobic Conditions

Candida albicans PDY-07 was isolated from activated sludge under anaerobic conditions and identified as a member belonging to the genus Candida. Pure culture of C. albicans PDY-07, biodegradation of 4-chlorophenol 4-CP was carried out under anaerobic conditions in Erlenmeyer flasks at 35℃, with an initial pH of 7.0—7.2 and a starting inoculum of 10% by volume. The results showed that, under the above-mentioned con- ditions, C. albicans PDY-07 could thoroughly biodegrade 4-CP up to a concentration of 300mg·L-1 within 244h and that it had a high tolerance potential of up to 440mg·L-1 for 4-CP. With the increase in the initial concentrations of 4-CP, substrate inhibition was obviously enhanced. There was increased consumption of 4-CP, which was not assimilated by the cell for growth but was used to counteract the strong substrate inhibition. In addition, the cell growth and substrate-degradation kinetics of 4-CP as the sole source of carbon and energy for the strain in batch cultures were also investigated over a wide range of substrate concentrations 2.2—350mg·L-1, using the proposed cell growth and degradation kinetic models. The results recorded from these experiments showed that the proposed kinetic models adequately described the dynamic behavior of 4-CP biodegradation by C. albicans PDY-07.

Laccase immobilized on magnetic nanoparticles by dopamine polymerization for 4-chlorophenol removal

In this work, a new immobilization method based on dopamine(DA) self-polymerization was developed for laccase immobilization on magnetic nanoparticles(Fe_3O_4 NPs). To optimize the immobilization condition including reaction pH, DA concentration and enzyme concentration, a central composite response surface method was applied. The optimal condition was determined as p H value of 5.92, laccase concentration of 0.25 mg mL^(-1) and DA concentration of 12.74 mg mL^(-1), under which a high enzyme activity recovery of 88.17% was obtained.By comparing with free laccase, the stabilities of immobilized laccase towards p H, thermostability, storage were enhanced significantly.Approximately 60% of relative activity for immobilized laccase was remained after being incubated for 6 h at 50℃, but the free laccase only remained 25%. After 40 days of storage at 4℃, the laccase immobilized by DA kept about 89% of its original activity, but the free laccase only retained 48%. After recycled 10 times, the relative activity of immobilized laccase still retained 70%. The immobilized laccase was then applied to catalyze the degradation of 4-chlorophenol(4-CP), 86% percentage of 4-CP was removed within 2 h. After degraded 10 times, the relative activity of immobilized laccase still remained 64% of its initial activity, which exhibits an excellent reusability and operational stability.

Synergistic photocatalytic effect of porous g-C_3N_4 in a Cr(Ⅵ)/4-chlorophenol composite pollution system

The photocatalytic reduction of aqueous Cr(VI)to Cr(III)was preliminarily studied using porousg‐C3N4as a photocatalyst under acidic conditions.The observed synergistic photocatalytic effect ofporous g‐C3N4on a Cr(VI)/4‐chlorophenol(4‐CP)composite pollution system was further studiedunder different pH conditions.Compared with single‐component photocatalytic systems for Cr(VI)reduction or4‐CP degradation,the Cr(VI)reduction efficiency and4‐CP degradation efficiency weresimultaneously improved in the Cr(VI)/4‐CP composite pollution system.The synergistic photocatalyticeffect in the Cr(VI)/4‐CP composite pollution system can be attributed to the acceleratedredox reaction between dichromate and4‐CP by electron transfer with porous g‐C3N4.

水溶液中4-氯酚的微波辅助光化学降解

研究了微波辅助无极紫外灯 (MW /UV)光化学降解 4 氯酚 (4CP)模拟废水 ;为了考察溶液中 4CP的降解效果 ,用紫外可见分光光度法 (UV VIS)和离子色谱法 (IC)测定了溶液中 4CP的降解率和Cl-浓度 .结果表明 ,MW /UV体系中 30mg/L 4CP反应 1 2 0min的降解率由紫外 (UV)光解体系的 2 1 5 6 %提高到 5 2 4 0 % .提高溶液的pH值、向体系通入氧气、增强光照度以及外加氧化剂H2 O2 均能增加水溶液中 4CP的降解率 .微波辅助光化学降解

微波辅助光催化降解4-氯酚的研究

采用了一种新的水处理技术微波辅助光催化(MW/UV/P25)降解4-氯酚(4CP)模拟废水。初始质量浓度为30mg/L的4CP在微波光催化下发生了降解,反应120min,4CP的降解率达到82.85%,Cl-质量浓度增加值为7.95mg/L。4CP的降解率与溶液的pH、通气条件、紫外灯光照度等因素有关,外加H2O2氧化剂能够加速4CP的降解。微波辅助光催化降解4CP服从一级反应动力学方程。

Fe^(2+)和Fe^(3+)在4-氯酚光化学反应中性质的相似性

研究在光照条件下，２０ｍｇ／Ｌ４－氯酚＋１ｍｇ／ＬＦｅ２＋（体系Ａ）和２０ｍｇ／Ｌ４－氯酚＋１ｍｇ／ＬＦｅ３＋（体系Ｂ）中Ｆｅ２＋和Ｆｅ３＋的浓度变化．通过离子色谱手段，在体系Ａ中能够同时检测出Ｆｅ２＋和Ｆｅ３＋，在体系Ｂ中亦能够同时检测到Ｆｅ２＋和Ｆｅ３＋．故Ｆｅ２＋和Ｆｅ３＋在４－氯酚光化学反应中的性质。

气液滑动弧放电降解4-氯酚溶液的研究

用10kV高压产生直接与废水接触的气液滑动弧放电非平衡等离子体降解水中4-氯酚。实验研究表明:由于液滴的存在改变了电极间的介电常数和局部电场,气液滑动弧放电的电压波形比纯气流滑动弧放电更加不规则,起弧电压更低:从溶液COD降解效果来看,当不锈钢作为电极材料时, 4-氯酚降解效果比铝和铜电极材料好;当空气作为载气时,经过76min的等离子体处理,溶液的COD值由1679.2mg／L降到190mg／L,相当于COD降解率为88．68％;增大气液混合比能够提高4-氯酚的降解效果;同时检测了H2O2和O3的生成量和溶液pH、电导率的变化。

钯/泡沫镍对水体中4-氯酚的氢解脱氯研究

采用置换沉积法制备泡沫镍负载钯（Pd/Ni）催化剂,研究了其在H2作为供氢体时对水相中4-氯酚（4-CP）的催化氢解脱氯作用.考察了Pd负载量、H2流量和反应液pH值对4-CP转化率的影响.结果表明,在相对较低的Pd负载量和H2流量下即可实现4-CP的快速高效去除,且反应液pH值在3.04-10.97的范围对反应影响不显著.当Pd负载量为0.1%、H2流量为10mL/min、pH值为6.80时,反应1h,4-CP转化率达92.6%.Pd/Ni具有较高的稳定性,重复实验表明,该催化剂使用3次后,催化活性仅下降了2.0%.

4-氯酚存在对生物强化系统降解2,4-二氯酚的影响研究

采用生物强化技术降解废水中的难降解有机物 2 ,4 二氯酚 (简称 2 ,4 DCP) ,研究了不同浓度的 4 氯酚 (简称 4 MCP)存在对 2 ,4 DCP降解的影响 ,并通过半连续流实验研究了 4 MCP长期存在下 ,强化系统中 2 ,4 DCP和 4 MCP降解速率的变化趋势 .结果表明 ,第 1次半连续流实验中 ,4 MCP浓度为 5、10、2 0及 30mg L时 ,都会对强化系统中 2 ,4 DCP的降解速率产生一定的抑制作用 ,而且抑制作用随着 4 MCP浓度的增加而增强 .随着半连续流实验次数的增加 ,4 MCP对 2 ,4 DCP降解的抑制作用减弱甚至消失 ,共基质时 2 ,4 DCP的降解速率反而比其单基质半连续流运行时快 .4 MCP与 2 ,4 DCP共基质存在时 ,2 ,4 DCP优先被微生物利用 ,此后 4 MCP才被降解 ,表现出两阶段降解的现象 .

4-氯酚光化学反应过程中C-Cl键的断裂

反应体系２０ｍｇ／Ｌ４－氯酚在光照条件下，Ｃ—Ｃｌ键断裂，用离子色谱检测了Ｃｌ－浓度．在模拟太阳光照射下，Ａｌ３＋加速Ｃ—Ｃｌ键断裂的作用较明显；在紫外光照射下，氯原子迅速从４－氯酚分子中苯环上断裂，Ａｌ３＋、Ｆｅ２＋、Ｆｅ３＋对该过程的影响很小．最后用Ｃｌ－浓度变化研究了反应体系的动力学性质．

零价铁对土壤中4-氯苯酚还原脱氯研究

氯苯酚是常见的环境污染物,它们在土壤中的加速分解可以减少对人类健康的危害。以恒温培养为方法,GC-MS为检测手段,研究了在常温常压下土壤中4-氯苯酚(4-CP)在零价铁作用下的还原脱氯反应。结果表明:4-CP可以被来自零价铁的电子还原,零价铁能够有效促进土壤中的4-CP脱除苯环上的氯原子,从而达到降低毒性、增加可生化性目的。反应条件如初始pH、时间、零价铁用量等均对4-CP还原脱氯效率有重要影响,特别是当初始pH值控制在偏酸时更有利于反应的进行。在零价铁加入量500mg、初始pH=4、反应时间7d的条件下,零价铁对土壤中4-CP还原脱氯效率最高可以达到65%。利用实验数据,对零价铁作用下4-CP还原脱氯的反应机理也进行了初步探讨。

4-氯酚在TiO_2纳米膜上光催化降解及反应动力学特征

TiO2/glass film was prepared by a solgel method with titanium tetrabutoxide as precursor,and used in photocatalytic degradation of 4Chlorophenol(4CP)in aqueous solution.The crystal type and size of TiO2 in film prepared in different experimental conditions were characterized by using XRD.The experiments indicated that the TiO2 particles in different film appear regular anatase structure with size about 833nm after heating treatment at 500℃ temperature,and the film coated 5 layers of TiO2 sol in the case of higher(pH≥10)and lower pH value(pH≤2) showed a higher catalytic activity.The relationship between initial 4CP concentration(C0) and reaction rate(r0) follow LangmuirHinshelwood equation,and the photocatalytic degradation of 4CP(C0≤07mmol·L-1)can be expressed by first order kinetics.

高压脉冲放电低温等离子体法降解废水中4-氯酚

考察了多种因素对高压脉冲放电低温等离子体法降解废水中 4-氯酚的影响。对降解过程所得的中间产物和终产物进行了分析。结果表明 ,提高脉冲电压峰值、延长放电时间、无机盐Fe SO4的存在均可提高降解效果 ,自由基清除剂及缓冲剂的存在会显著降低降解效果。对 1 0 0 mg/ L4-氯酚废水放电处理 2 4 0 min,最高降解率可达 90 %以上 ,降解产物主要有苯酚、对苯二酚、邻苯二酚、对氯邻苯二酚和对苯醌等。当放电时间足够长时 ,4-氯酚可完全降解为 CO2 和 H2

Pd-Ni双金属复合物修饰泡沫镍电极对水中4-氯酚的电化学脱氯

The electrocatalytic dechlorination of 4-chlorophenol(4-CP) in aqueous solution was studied by using a palladium-nickel bimetallic composite catalyst deposited on nickel foam(Pd-Ni/Ni foam) as the cathode.The Pd-Ni composite particles with a diameter of less than 50 nm were finely dispersed on the Ni foam surface.The Pd-Ni/Ni foam electrode exhibited higher dechlorination efficiency than single Pd or Ni supported on Ni foam electrodes.High-performance liquid chromatography analysis verified that phenol was the main dechlorination product.For an applied current of 20 mA,a bulk solution temperature of 15℃,and an initial 4-CP concentration of 1 mmol·L-1,dechlorination efficiency of 82% was observed.Based on electrochemical impedance spectroscopic results and the current efficiency of 4-CP dechlorination at different applied currents on various electrodes,the authors determined the rate-limiting step under various polarization conditions in the experiments.

高分散型纳米级Pd/Fe对4-氯苯酚的还原脱氯

氯酚类化合物在医药、农药、塑料、抗氧剂、涂料、制革和造纸等生产过程中有着广泛的应用，是首批列入斯德哥尔摩国际公约的12类持久性有机污染物（POPs）之一，属于典型的环境雌激素[1]。因此，如何修复氯酚类化合物对环境的污染已成为当今环境科学界迫切需要解决的问题。

N掺杂纳米TiO_2在4-氯苯酚中的可见光催化活性及动力学研究

以NH4Cl为氮源,采用溶胶-凝胶法制备N掺杂纳米TiO2,以4-氯苯酚和TOC降解率为指标,考察灼烧温度、搅拌速度、溶液pH值等因素对N掺杂TiO2可见光活性及动力学方程的影响。结果表明,N掺杂TiO2对4-氯苯酚具有良好的降解作用,在灼烧温度400℃、快速搅拌、pH值为4.6下,4-氯苯酚降解率最大,在可见光辐射6h时达到87%。降解反应符合Langmuir-Hinshelwood动力学方程。