硫脲改性活性炭及吸附金性能研究

Study on properties of activated carbon modified by thiourea and adsorption of gold

为了改善活性炭吸附性能,利用硫脲溶液在超声波辅助条件下对活性炭进行改性,探究了不同改性及吸附条件下的吸附金的效果,利用场发射扫描电镜(SEM)及傅里叶红外光谱仪(FT-IR)对改性前后的活性炭孔结构和表面特性进行表征。结果表明,最佳改性条件为3 mol/L的硫脲溶液,温度为95～100℃,时间为3 h;吸附环境适宜pH值为2～2.5,投入0.5 g改性炭,吸附时间为1.5 h,吸附率达到97%。表征发现,改性后活性炭孔结构明显,比表面积增大。硫脲的加入改变了原有基团的波谱峰,同时产生了新基团,如—NH_2、■、C—H、■等,增强炭的吸附。改性炭的吸附等温线符合Langmuir与Freundlich等温线模型,表明改性炭的吸附模式是以单分子层吸附为主与多层吸附共同作用的吸附模式,拟合后得到的饱和吸附容量为0.208 mmol/g,实际得到的饱和吸附容量为(0.194 mmol/g),吸附效果较好。

In order to improve the adsorption performance of activated carbon,the activated carbon was modified by thiourea solution under ultrasonic assisted conditions.The effect of gold adsorption under different modification and adsorption conditions was investigated.Field emission scanning electron microscopy(SEM)and Fourier infrared spectrometer(FTIR)were used to characterize pore structure and surface properties of activated carbon before and after modification.The results shows that the optimal modification condition was thiourea solution of 3 mol/L,temperature of 95-100℃,time of 3 h,suitable pH value of the adsorption environment of 2-2.5,modified carbon added of 0.5 g,and adsorption time of1.5 h.Under the toptimal modification condition,the adsorption rate reached 97%.According to the characterization,the activated pore structure of activated carbon was obvious,and the specific surface area increased.The addition of thiourea changed the spectral peaks of the original group,and new groups such as-NH 2,C═O,C-H,and C═S were formed to enhance the adsorption of carbon.The adsorption isotherm of the modified charcoal accorded with the Langmuir and Freundlich isotherm model,showing that the adsorption mode of the modified charcoal was the adsorption mode in which monolayer adsorption dominated with multilayer adsorption.The saturated adsorption capacity after fitting was 0.208 mmol/g and the actual saturated adsorption capacity was(0.194 mmol/g),showing the better adsorption effect。