微波制备碱木质素生物炭对Zn^(2+)的吸附性能及机理

ADSORPTION PERFORMANCE AND MECHANISM OF Zn^(2+)ON MICROWAVE-PREPARED ALKALI LIGNIN BIOCHAR

碱木质素是造纸工业的主要副产品。为探索碱木质素资源化利用的可行途径,以碱木质素为原料,在微波热解条件下制备得到生物炭,并研究了生物炭对水体中Zn^(2+)的吸附性能和吸附机理。结果表明:在炭化温度为400℃,投加量为0.4 g/L,Zn^(2+)初始浓度为200 mg/L,pH为5的吸附条件下,碱木质素生物炭对Zn^(2+)的平衡吸附量达到313.7~326.7 mg/g,为最佳吸附效果;准二级动力学模型和Langmuir模型能更好地拟合碱木质素生物炭对Zn^(2+)的吸附过程,说明生物炭的吸附速率受化学吸附机制的控制,且由Langmuir模型拟合得到生物炭对Zn^(2+)的最大吸附量(qm)为371.3~412.3 mg/g;吸附机理研究表明,碱木质素生物炭对Zn^(2+)的吸附机理包括矿物共沉淀作用、DOM吸附作用、表面络合作用(含氧官能团络合和Zn^(2+)-π配位作用)和离子交换作用。此外,生物炭吸附机理量化分析结果表明,矿物共沉淀和表面络合作用对生物炭吸附量的贡献分别为81.8%~85.6%和7.6%~9.9%。

Alkali lignin is the major by-product of the paper-making industry.In order to explore a feasible way for resource utilization of alkali lignin,biochar was prepared from alkali lignin under microwave pyrolysis,and the adsorption performance and mechanism of biochar were further investigated in this paper.The results showed that the best adsorption effect of biochar was achieved under the adsorption condition of a charring temperature of 400℃,a biochar dosage of 0.4 g/L,an initial Zn^(2+)concentration of 200 mg/L,and solution pH=5;the adsorption process could be well described by the Langmuir model and the quasi-secondary kinetic model,indicating that the adsorption process was dominated by chemisorption,and the maximum adsorption capacity(qm)of biochar calculated from the Langmuir fitting reached 371.3 to 412.3 mg/g;the adsorption mechanism analysis of biochar revealed that the mechanisms mainly include mineral co-precipitation,DOM interaction,surface complexation(O-functional group complexation and Zn^(2+)-πcomplexation),and ionic exchange.In addition,the results of quantitative analysis of the adsorption mechanism showed that mineral co-precipitation and surface complexation contributed 81.8%~85.6%and 7.6%~9.9%to the adsorption capacities of biochars,respectively.