芦苇秸秆生物炭对水中菲和1,1-二氯乙烯的吸附特性

Sorption Characteristics of Phenanthrene and 1,1-Dichloroethene onto Reed Straw Biochar in Aquatic Solutions

在500℃热解温度下自制芦苇秸秆生物炭吸附剂,研究生物炭对水中两种典型有机污染物菲(PHE)和1,1-二氯乙烯(1,1-DCE)的吸附特性,探讨其吸附机制,并考察溶液p H和生物炭投加量对吸附效果的影响.结果表明,生物炭对PHE和1,1-DCE的吸附分别在60 min和480 min时达到平衡,最大去除率分别为81.87%和90.18%,两者的吸附动力学规律均符合准二级动力学方程,其中PHE的二级动力学吸附速率大于1,1-DCE,两者的吸附过程均由膜扩散和颗粒内扩散共同控制,且后者是主要限速步骤;两种有机污染物的等温吸附曲线均可用Freundlich方程描述,且生物炭对1,1-DCE的吸附亲和力强于PHE;PHE和1,1-DCE在生物炭上的吸附机制包括表面吸附作用和分配作用,且以表面吸附作用为主,其中1,1-DCE的表面吸附作用大于PHE,而其分配作用小于PHE,说明污染物性质中分子体积和相对极性是影响总体吸附的主要因素;红外图谱显示,含氧、含氢官能团及π—π相互作用对生物炭吸附两种有机污染物有重要贡献;溶液p H对生物炭吸附PHE和1,1-DCE的影响较小,而生物炭投加量从5增至50 mg时,PHE和1,1-DCE的平衡吸附量分别减少6.78倍和2.18倍,去除率分别提高20.21%和15.78%.

The purpose of this study was to investigate the sorption characteristics of phenanthrene（ PHE） and 1,1-dichloroethene（ 1,1-DCE） onto reed straw biochar at 500℃ in aquatic solutions. The sorption mechanisms and effects of solution p H and biochar mass on sorption intensity were discussed. The results showed that the time required to reach sorption equilibrium was 60 min and 480 min for PHE and 1,1-DCE,respectively,with maximum removal rates of 81. 87% and 90. 18%. The sorption kinetics of both PHE and 1,1-DCE fitted the pseudo-second-order model well,but the pseudo-second-order reaction rate of PHE was higher than that of 1,1-DCE.Furthermore,the sorption processes were controlled by both membrane diffusion and intra-particle diffusion,and the latter was found to be the rate-controlling step. Sorption isotherms of the two organic pollutants fitted well with the Freundlich equation,and the sorption affinity of 1,1-DCE onto biochar was greater than that of PHE. The total sorption mechanism of biochar was the combination of partition and adsorption,and dominated by adsorption. The adsorption capacity of 1,1-DCE was greater than that of PHE,but its partition capacity was much smaller,indicating that pollutants＇ molecular volume and relative polarity would mainly affect the total sorption.Analysis of Fourier transform infrared spectroscopy（ FTIR） demonstrated that oxygen- and hydrogen- containing functional groups andπ—π interaction were important for PHE and 1,1-DCE sorption onto biochar. The solution p H value had no significant effect on the sorption intensity of PHE and 1,1-DCE,however,with biochar mass increasing from 5 mg to 50 mg,the equilibrium sorption amount of PHE and 1,1-DCE decreased by 6. 78 times and 2. 18 times,and the removal rate increased by 20. 21% and 15. 78%,respectively.