Catalytic dechlorination of o-cllorophenol 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.     

Pd/Fe及纳米Pd/Fe对氯酚的脱氯研究

采用化学沉淀法制备得到了纳米Fe和纳米Pd/Fe(20～100nm),利用制备的纳米催化剂对氯酚进行了催化脱氯研究,并与常规的零价铁和Pd/Fe进行了对比分析.结果表明,纳米颗粒具有较高的比表面积和表面反应活性,所制备的纳米Pd/Fe双金属BET比表面积达到12.4m²/g,而商用铁颗粒(<10m)的比表面积只有0.49m²/g;当钯化率为0.0666%,纳米Pd/Fe用量在6g/L时,氯酚脱氯率达到90%以上,在相同的处理效果下,常规Pd/Fe的使用量为纳米Pd/Fe的20倍左右,纳米Pd/Fe催化氯酚的脱氯降解遵循一级反应动力学.     

Dechlorination of disinfection by-product monochloroacetic acid in drinking water by nanoscale palladized iron bimetallic particle

Nanoscale palladized iron(Pd/Fe)bimetallic particles were prepared by reductive deposition method.The particles were characterized by X-ray diffraction(XRD),X-ray fluorescence(XRF),scanning electron microscope(SEM),transmission electron microscope(TEM),and Brunauer-Emmett-Teller-nitrogen(BET-N_2)method.Data obtained from those methods indicated that nanoscale Pd/Fe bimetallic particles containedα-Fe~0.Detected Pd to Fe ratio by weight(Pd/Fe ratio)was close to theoretical value. Spherical granules with di...     

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.     

纳米镍/铁和铜/铁双金属对四氯乙烯脱氯研究

以实验室合成的纳米双金属颗粒(Ni/Fe和Cu/Fe)为反应材料,对四氯乙烯(PCE)进行脱氯试验研究.纳米金属颗粒(直径范围在1～100nm)比表面积比微米级铁颗粒高数十倍.结果表明,纳米Ni/Fe和Cu/Fe对四氯乙烯有明显的脱氯作用,且脱氯反应符合准一级反应动力学方程;在作为还原剂的铁表面镀上一薄层起催化作用的金属Ni或Cu,催化剂的存在大大降低脱氯反应活化能,提高了脱氯速率,并减少氯代副产物的产量.与零价铁及微米级双金属系统(Ni/Fe,Cu/Fe)相比,纳米颗粒对PCE的脱氯速率有明显提高,尤其是纳米Ni/Fe,标准化反应速率常数KSA为4.283 mL·m-2·h-1,分别比零价铁和微米级Ni/Fe系统快33.23倍和11.59倍.纳米Cu/Fe标准化反应速率常数KSA为1.194 mL·m-2·h-1,分别比零价铁和微米级Cu/Fe双金属系统快9.26倍和5.24倍.在相同条件下,纳米Ni/Fe脱氯速率常数KSA是纳米Cu/Fe的3.59倍.     

金属催化还原技术对p-二氯苯的脱氯

研究了Pd/Fe双金属体系对p-二氯苯(p-DCB)的快速催化还原脱氯处理. 结果表明, 在Pd的催化作用下,零价Fe对p-DCB具有较好的还原脱氯效率. 当Pd/Fe双金属的钯化率为0.02%,催化还原剂的用量为4g/75mL,反应90min p-DCB脱氯率达到90%以上;p-DCB的脱氯效率与溶液初始pH值、反应温度、钯化率、Pd/Fe投加量等因素有关;p-DCB在催化还原脱氯过程中先生成氯苯,而后继续脱氯生成苯.     

Ni/Fe二元金属脱氯降解对氯苯酚的研究

研究了Ni/Fe二元金属脱氯降解对氯苯酚的催化性能.结果表明,吸附氢原子是对氯苯酚脱氯降解的主要还原剂,发生在催化剂表面的化学反应为整个过程的速率控制步骤.质量分数为2.96%Ni的催化剂具有最大的比表面积,在相同条件下也具有最好的脱氯性能,90min时的脱氯效率达64%.对不同Ni含量催化剂脱氯的动力学研究表明,对氯苯酚脱氯的表观动力学方程为一级反应,而且反应速率常数正比于催化剂的比表面积.通过计算表明,Ni/Fe单位比表面的表观速率常数为(κ′)为7.61×10^-4min^-1·m^-2.当体系温度小于43℃时,脱氯效率随着温度的上升而加快,超过这一温度后,升高温度反而会使体系的脱氯效率下降.     

Catalytic reductive dechlorination of p–chlorophenol in water using Ni/Fe nanoscale particles

Nanoscale bimetallic Ni/Fe particles were synthesized from the reaction of sodium borohydride （NaBH4） with reduction of Ni^2＋ and Fe^2＋ in aqueous solution. The obtained Ni/Fe particles were characterized by TEM （transmission electron microscope）, XRD （X-ray diffractometer）, and N2-BET. The dechlorination activity of the Ni/Fe was investigated using p-chlorophenol （p-CP） as a probe agent. Results demonstrated that the nanoscale Ni/Fe could effectively dechlorinate p-CP at relatively low metal to solution ratio of 0.4 g/L （Ni 5 wt%）. The target with initial concentration ofp-CP 0.625 mmol/L was dechlorinted completely in 60 rain under ambient temperature and pressure. Factors affecting dechlorination efficiency, including reaction temperature, pH, Ni loading percentage over Fe, and metal to solution ratio, were investigated. The possible mechanism of dechlorination ofp-CP was proposed and discussed. The pseudo-first- order reaction took place on the surface of the Ni/Fe bimetallic particles, and the activation energy of the dechlorination reaction was determined to be 21.2 kJ/mol at the temperature rang of 287-313 K.     

Enhanced catalytic degradation process of o-nitrochlorobenzene by palladium-catalyzed Fe0 particles

Over Pd/Fe bimetallic catalyst, o-nitrochlorobenzene（o-NCB）, at a concentration of 20 mg/L in aqueous solutions, is rapidly converted to o-chloroaniline（o-CAN） first, and then quickly dechlorinated to aniline（AN） and Cl^- , without other intermediate reaction products. The aminated and dechlorinated reactions are believed to take place on the surface site of the Pd/Fe. The o-NCB removal efficiency and the next dechlorination rate increase with an increase of bulk loading of palladium and catalysts addition due to the increase of both the surface loading of palladium and the total surface area. These results indicate that reduction, amination and dechlorination of o- NCB by palladium-catalyzed Fe^0 particles, can be designed for remediation of contaminated groundwater.     

凹凸棒土--粉煤灰颗粒吸附剂的制备及改性

研究了凹凸棒土—粉煤灰颗粒吸附剂的制备方法并对其进行再生和改性，利用比表面积测定、X射线能谱等手段对所制吸附剂进行了表征。结果表明：制备颗粒吸附剂的优化条件为凹凸棒土：粉煤灰=100：40(质量比)，比表面积的值为80．06m^2／g。该吸附剂可采用1mol/L磷酸进行改性，改性后的比表面积为155．6m^2／g。