以天然磁铁矿作为吸附材料,通过静态批式实验考查了pH 值对磁铁矿吸附 Pb2＋的影响,并研究了该吸附剂对Pb2＋的等温吸附动力学特性,同时利用XRF和 SEM对吸附前后的磁铁矿进行表征,探讨该吸附剂去除水中Pb2＋的作用机制.研究结果表明,随着反应初始pH 值的增加,磁铁矿对 Pb2＋的吸附作用不断增加,当pH 值＝6时,其最大吸附率为97．80％.磁铁矿对水中 Pb2＋的吸附热力学等温线符合 Lang-muir方程.当吸附剂粒径为120~150μm、用量20 g/L时,在温度30℃,pH 值＝5,160 r/min 振荡30 min时其饱和吸附量达16．98 mg/g.磁铁矿对 Pb2＋的吸附作用可以用准二级动力学模型Y＝0．0986X＋0．5435描述,其相关系数R2为0．992,吸附速率常数K2为0．018(g·mg-1)/min.研究结果还表明,磁铁矿所吸附的 Pb 以氧化态形式(PbO 和 Pb2 O3)存在,磁铁矿对 Pb2＋的去除机制包括表面沉积、离子交换、物理吸附和化学吸附等综合作用的结果.
In the present investigation,the natural magnetite was employed in studies on the adsorption effects of pH during the removal of Pb(Ⅱ)ions from aqueous solutions by static batch experiments,and the adsorp-tion kinetics and isotherms were also studied.The magnetite was characterized by SEM and XRF before and af-ter sorption in order to analyze the mechanism on Pb2+ adsorption.The results demonstrated that it had a better efficiency on Pb2+ adsorption as the initial pH value increased and the adsorption rate was 97.8% while pH value was 6.When the conditions were magnetite particle size 120-150μm (100-120 mesh),magnetite initial concen-trations 20 g/L,pH value 5,temperature 30 ℃ and shaker rotational for 30 min at speed of 160 r/min,respec-tively,the saturated adsorption capacity was 16.98 mg/g.It was concluded that the Langmuir isotherm was more suitable to fit equilibrium adsorption data,and the adsorption kinetic data for Pb2+ onto magnetite parti-cles fitted by pseudo-second-order equations withY=0.0986X+0.5435 model,R2=0.9923 and K2=0.0179 (g ·mg-1 )/min.Furthermore,Pb2+ adsorbed onto the magnetite existed in PbO or Pb2 O3 .The removal mecha-nism of Pb2+by natural magnetite contains the coordinated actions of superficial deposit,ion exchange,physical adsorption and chemical adsorption.
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