摘要
近年来我国城市饮用水中不断出现硝酸盐超标的问题,严重影响了饮用水水质,威胁人体健康。为了进一步提高去除水中硝酸盐的效果,我们研发了一种经济高效的水中硝酸盐吸附剂——十八烷基三甲基氯化铵改性煤基活性炭(OTAC-GAC),采用正交实验方法确定了OTAC-GAC的最优制备条件和对水中硝酸盐的最大吸附效能,并通过动力学吸附拟合和表面物化特性分析探究了OTAC-GAC对水中硝酸盐的吸附机理。研究表明,当以煤基活性炭为母体、以OTAC为改性剂时,季铵盐改性煤基活性炭的最佳制备条件为:改性剂浓度5 mmol/L,改性温度20℃,改性时间2 h;优化后的OTAC-GAC对硝酸盐的最大吸附量为22.05 mg/g,比改性前提高了15.31 mg/g,且OTAC-GAC对硝酸盐的吸附符合准二阶动力学吸附模型(R^2=0.999)、Langmuir等温吸附模型(R^2=0.913)和D-R等温吸附模型;此外,与改性前相比,OTAC-GAC的总孔容量减少了47%,N元素含量提高了44%,碱性官能基团含量增加了3.4倍,说明改性后带正电、含氮的OTAC已成功负载在煤基活性炭表面孔隙内,从而可推测出改性煤基活性炭去除硝酸盐的主要机理为离子交换和静电吸附作用,为保障饮用水安全奠定了理论基础。
In recent years,the problem of excessive nitrate in urban drinking water in China has seriously influence on the drinking water quality and threatened human health. In order to further improve efficiency of removal nitrate from water,this study herein developed an economic and efficient nitrate adsorbent-octadecyltrimethyl ammonium chloride modified coal-based granular activated carbon(OTAC-GAC). The optimal preparation conditions and the maximum nitrate adsorption capacity of OTAC-GAC were determined by orthogonal experiment method. The adsorption mechanism of nitrate on OTAC-GAC was investigated by dynamic adsorption modeling and surface characterization. The results show that the optimum condition of anchoring QA onto GAC is achieved at the OTAC concentration of 5 mmol/L,the reaction temperature of 20 ℃ and the reaction time of 2 h,the optimized OTAC-GAC exhibits higher nitrate adsorption capacity(22. 05 mg/g) than that of the pristine GAC(15. 31 mg/g).The adsorption performance fits the pseudo-second-order model( R^2= 0. 999),Langmuir adsorption model( R^2= 0. 913) and D-R adsorption model very well. Besides,compared to the pristine GAC,the pore volume of the optimized OTAC-GAC decreased by 47%,the nitrogen amounts of increased by 44%,and the basic functional group increased by 3. 4 times,indicating the OTAC that hosts positively-charged nitrogen successfully anchored into GAC pores. Therefore,it can be predicted that adsorption mechanism of nitrate on the OTAC-GAC includes ion exchange and electrostatic adsorption,which provid a theoretical support for maintaining drinking water safety.
出处
《矿业科学学报》
2017年第6期595-603,共9页
Journal of Mining Science and Technology
基金
国家自然科学基金(51508555)
北京市自然科学基金(8152025)
中央高校基本科研业务费专项资金(2014QH01)
