纳米镍-铁/介孔氧化铝的制备及其三氯乙烯还原脱氯活性研究

PREPARATION OF BIMETALLIC Ni-Fe NANOPARTICLES SUPPORTED ON MESOPOROUS ALUMINA FOR REDUCTIVE DECHLORINATION TOWARD TRICHLOROETHYLENE

将纳米镍-铁双金属粒子负载于介孔氧化铝,使其分散性、悬浮稳定性、脱氯能力及活性持久性均得到极大提高,可更高效地用于脱氯降解地下水中的氯代烃。首先制备介孔氧化铝载体,其最可几孔径、孔容和比表面积分别为7.65 nm、0.68 cm^(3)/g和350 m^(2)/g;然后采用水解共沉淀-氧化-晶化法制得镍-铁层状双金属氢氧化物/介孔氧化铝,将其在10%H_(2)中400℃煅烧后得到纳米镍-铁(FeNi_(3))/介孔氧化铝。因介孔氧化铝对纳米镍-铁的分散作用及介孔结构的限域效应,其上纳米镍-铁(FeNi_(3))粒子分散均匀,晶粒小至11.5 nm;而未被负载的纳米镍-铁粒子发生团聚,粒径为50~100 nm。纳米镍-铁/介孔氧化铝的水悬浮液12 h仍未沉降,而纳米镍-铁在2 min内完全沉降。采用地下水中三氯乙烯平均浓度1000倍作为初始浓度(23.7 mg/L),经48 h反应,纳米镍-铁/介孔氧化铝对三氯乙烯的转化率为12.03%,比纳米镍-铁提高了约9倍;同时三氯乙烯仅剩余0.41%,说明纳米镍-铁/介孔氧化铝也具有优异的吸附性能。纳米镍-铁/介孔氧化铝在重复使用的第4周期仍与第1周期活性相同,48 h后的二碳烃总生成量均为0.23μmol;至第8周期仍有吸附和脱氯能力,48 h后三氯乙烯去除量和二碳烃总生成量分别为1.05,0.043μmol;说明其具有优异的活性持久性。因此纳米镍-铁/介孔氧化铝是一种非常有前景的氯代烃污染地下水修复材料。

Bimetallic nickel-iron nanoparticles were supported on mesoporous alumina in order to improve their dispersion performance,suspension ability and mobility in groundwater,as well as aqueous dechlorination reactivity and reactive longevity toward chlorinated organic contaminants in groundwater.Mesoporous alumina with a pore diameter of 7.65 nm,a pore volume of 0.68 cm^(3)/g,and a specific surface area of 350 m^(2)/g was prepared.Then bimetallic Ni-Fe(FeNi_(3))nanoparticles were produced on mesoporous alumina by calcining in hydrogen gas(10%by volume)at 400℃.A nickel-iron layered double hydroxides was impregnated onto the carrier.Bare Ni-Fe nanoparticles were 50~100 nm in diameter and agglomerated together.In comparison,the crystallite size of the supported Ni-Fe nanoparticles decreased to 11.5 nm due to the interfacial interaction between the nanoparticles and the mesoporous alumina,and the confinement effect of the mesoporous structure.In addition,the dispersion performance of the supported Ni-Fe nanoparticles was dramatically enhanced.The composite of Ni-Fe nanoparticles and mesoporous alumina,i.e.,Ni-Fe-nanoparticles/mesoporous-alumina,remained suspending in water within 12 h,whereas bare Ni-Fe nanoparticles precipitated in merely 2 min.When trichloroethylene was loaded at an initial concentration of 23.7 mg/L,i.e.,1000 times the average concentration in groundwater,the overall yield of two-carbon hydrocarbons was 12.03%in 48 h by the supported Ni-Fe nanoparticles,which was approximately 9 times greater than the bare counterpart.Furthermore,Ni-Fe-nanoparticles/mesoporous-alumina showed excellent adsorption activity,and only 0.41%of trichloroethylene remained in 48 h.The composite showed a remarkable reactive longevity in multi-run use,with the yield of two-carbon hydrocarbons during the 4th run being the same as the 1st run(0.23μmol).Furthermore,it still exhibited adsorption and dechlorination activity until the 8th run,during which the degradation of trichloroethylene and yield of two-carbon hydrocarbons were 1.05μmol and 0.043μmol,respectively.The results indicate that the composite is a promising material for remediation of groundwater contaminated by chlorinated organic compounds.