摘要
ZnO,NiO and ZnO@NiO nanocrystals were successfully synthesized and characterized by FTIR,XRD and SEM methods.The average particles sizes of ZnO,NiO and ZnO@NiO were32,50and48nm,respectively.The nanocrystals were examined assensors for cyanide removal.The cyanide sensing test revealed that,compared with the pure ZnO,NiO,the ZnO@NiO nanocrystalsexhibited highly improved sensing performances.The ZnO@NiO nano crystals were found to have better capacity for iron cyanidethan sodium cyanide.The effects of significant parameters such as contact time,pH(2-12),nanocrystal dose(0.02-0.4g)andcyanide concentration(5-50mg/L)on the removal of cyanide by nanocrystals were explored.At an optimum pH<5,over90%removal of20mg/L cyanide was obtained for nanocrystal dose of0.2g after30min contact time for iron cyanide by ZnO@NiOnano crystals.Cyanide removal was followed by pseudo second order kinetic model for ZnO@NiO nano crystals(k2=4.66×10-2andR2=0.999).The values of standard entralpy change of7.87kJ/mol and standard free energy change of-18.62kJ/mol at298K suggestthe adsorption of cyanide on nanocrystals is an endothermic and spontaneous process.ZnO@NiO nanocrystal is an efficient sensorfor removal of cyanide from water and wastewater.
合成了ZnO、NiO和ZnO@NiO纳米晶粒,采用红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)技术对其进行表征。ZnO、NiO和ZnO@NiO的平均颗粒尺寸为32、50和48 nm。对这些纳米晶粒去除氰化物的能力进行了测定。实验结果表明,与ZnO和NiO相比较,ZnO@NiO纳米晶粒去除氰化物的能力更强。ZnO@NiO纳米晶粒对氰化铁的去除能力比对氰化钠的更高。研究了反应时间、溶液pH值(2~12)、纳米晶粒用量(0.02~0.4 g)和氰化物浓度(5~50 mg/L)等参数对氰化物去除效果的影响。在最优条件下:pH<5,纳米晶粒用量0.2 g,反应时间30 min,ZnO@NiO纳米晶粒对20 mg/L氰化物的去除率可达到90%以上。ZnO@NiO纳米晶粒对氰化物的吸附去除动力学影响规律符合Langmuir准二级吸附动力学模型(k2=4.66×10-2,R=0.999)。热力学研究表明,25°C下,反应的标准焓变化为7.87 kJ/mol,自由能变化为-18.62 kJ/mol。纳米晶粒对氰化物的吸附是一个吸热的自发过程。ZnO@NiO纳米晶粒是一种能有效的去除水或废水中氰化物的吸附剂。
基金
financial support from the Research Council of Islamic Azad University of Yazd
