改性梨树枝吸附废水中Pb2+和Cd2+研究

Adsorption of Pb and Cd from Wastewater by Modified Pear Branches

为减少水体重金属污染并实现林业废弃物资源化利用,文章研究了NaOH改性前后梨树枝对废水中Pb2+和Cd2+的吸附特性和动力学、吸附等温模型与热力学过程。结果表明,改性增加梨树枝表面孔隙、交换性离子和表面C-H、C=C、-OH等官能团数量。随投加量增加,梨树枝对Pb2+和Cd2+吸附量呈乘幂函数下降(P<0.05),而改性梨树枝对Pb2+和Cd2+吸附量呈对数下降(P<0.05);随pH升高,2种材料对Pb2+和Cd2+吸附量先增大后减小。吸附符合准二级动力学模型且Langmuir模型和Freundlich模型均可模拟它们对Pb2+和Cd2+的等温吸附过程。改性梨树枝对Pb2+和Cd2+最大吸附量分别为238.59和80.34 mg/g,是梨树枝的4.74倍和1.92倍。Pb2+和Cd2+吸附是放热反应,温度升高不利于反应进行。改性梨树枝对实际废水中Pb2+和Cd2+的去除率分别为84.39%和81.61%,均高于梨树枝,在去除废水中重金属有良好的应用前景。

In order to reduce the pollution of heavy metals from water and realize the resource utilization of forestry wastes,the pear branch(PEBR)and the NaOH-modified pear branch(M-PEBR)were prepared and their adsorption characteristics for Pb2+and Cd2+in wastewater were performed.The Pb2+and Cd2+adsorption mechanisms by these two materials were also conducted by adsorption kinetics,adsorption isothermal models,and thermodynamics process.The porosity,exchangeable ions,and active functional group of PEBR increased obviously after modification.The adsorption capacities of Pb2+and Cd2+by PEBR decreased as power functions(P<0.05)while those by M-PEBR decreased logarithmically(P<0.05)with the increase of dosage in simulated water.With the increase of initial pH,the adsorption capacities of Pb2+and Cd2+by these two materials increased first and then decreased.The quasi-second-order kinetic model could be used to effectively describe the adsorption process.Both of Langmuir model and Freundlich model could simulate isothermal adsorption effectively.The maximum adsorption capacities of Pb2+and Cd2+by M-PEBR were 238.59 and 80.34 mg/g,respectively,which was 4.74 and 1.92 times higher than that of PEBR.The adsorption reactions were exothermic and the increase of temperature was disadvantageous to the reactions.The removal rates of Pb2+and Cd2+in practical wastewater by M-PEBR were 84.39%and 81.61%,both of which were higher than PEBR.Therefore,the modified pear branch can be feasible adsorbent of heavy metal removal from wastewater.