Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd/Fe

Nanoscale Pd/Fe bimetallic particles were synthesized with an efficient method to dechlorinate o-chlorophenol. The nanoscale Pd/Fe particles were determined by transmission electron microscopy and BET specific surface area analysis. Most of the particles are in the size range of 20—100 nm. The BET specific surface area of synthesized nanoscale Pd/Fe particles is 12.4 m 2/g. In contrast, a commercially available fine iron powder(<100 mesh) has a specific surface area of 0.49 m 2/g. Batch studies demonstrated that the nanoscale particles can effectively dechlorinate o-chlorophenol. The dechlorination reaction takes place on the surface of synthesized nanoscale Pd/Fe bimetallic particles in a pseudo-first order reaction. The surface-area-normalized rate coefficients(k_ SA) are comparable to those reported in the literature for chlorinated ethenes. The observed reaction rate constants(k_ obs) are dominated by the mass fraction of Pd and the mass concentration of the nanoscale Pd/Fe particles.

Catalytic dechlorination of o-chlorophenol by nanoscale Pd/Fe

Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20—100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder(<100 mesh) has a specific surface area of just 0\^49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

纳米Pd/Fe双金属对2,4-二氯酚的脱氯机理及动力学

采用纳米Pd Fe双金属对2,4 二氯酚(2,4 DCP)进行了催化还原脱氯处理.结果表明,纳米Pd Fe双金属具有较高的比表面积和反应活性,对2,4 DCP具有较好的脱氯效率.当纳米Pd Fe用量在6g·L-1时,2,4 DCP脱氯率达到90%以上;脱氯效率与pH值、温度、钯化率、Pd Fe投加量等因素有关.2,4 DCP在脱氯过程中先生成邻氯酚和对氯酚,而后继续脱氯生成苯酚,或由2,4 DCP直接降解成苯酚.2,4 DCP降解符合拟一级反应动力学.2,4 DCP催化还原脱氯反应的活化能为139 7kJ·mol-1.

负载型纳米Pd/Fe对挥发性氯代烃的去除

氯代烃的污染治理已成为当今世界最热门的研究领域之一。以水体中最常见的氯代烃污染物1,1-二氯乙烯(1,1-DCE)、林丹(γ-HCH)为主要目标污染物,探讨了不同条件下负载型纳米Pd/Fe对氯代烃的去除效果。负载型纳米Pd/Fe采用浸渍→液相还原→还原沉淀的方法制备,透射电镜显示采用该方法制备的负载型金属钯和铁的平均粒径均在纳米级范围内。负载型纳米Pd/Fe具有较高的表面反应活性,当负载型纳米Pd/Fe用量为40 g/L、反应时间达2 h时,1,1-二氯乙烯和林丹的去除率分别达到85%和100%。脱氯率与Pd/Fe投加量、钯含量、初始pH值、反应温度等因素有关,与溶液的初始浓度关系不大。负载型纳米Pd/Fe对1,1-DCE和γ-HCH去除均符合一级反应动力学方程,速率常数分别为0.528 3 h-1及2.012 9 h-1,反应的半衰期t1/2分别为1.31 h和0.34 h。推断在反应过程中,Fe腐蚀产生的H2为主要还原剂,Pd是良好的加氢催化剂,在金属颗粒表面形成高浓度反应相,使反应短时间内完成。