锑/磷在膨润土和高岭土的竞争吸附

采用批处理法研究了锑/磷(Sb/P)在膨润土和高岭土上的竞争吸附等温线和动力学,并考察了pH的影响。结果表明:Sb和P吸附符合Langmuir或Freundlich方程(R~2=0.945 0~0.998 3,P0.000 1),存在极强的竞争吸附:P共存时Sb吸附容量(Q_(max))显著降低,分别从0.86和10.21 mmol/kg(先Sb后P)降低到0.64和2.61 mmol/kg(先P后Sb);Sb共存时P吸附亲合性(K)明显降低,分别从1.47和7.47 L/mmol(先P后Sb)降低到0.68和2.34 L/mmol(先Sb后P)。Sb和P的吸附总体随pH升高而降低,但相比高岭土,膨润土上的吸附受pH影响更大,意味着高岭土有更多配位吸附、膨润土有更多电性吸附。准二级动力学方程很好地拟合它们的竞争吸附(R~20.994,P0.000 1),并且在Sb/P共存下,膨润土对P吸附弱而慢(q_e=0.36 mmol/kg,,k_2=0.064 6 kg/(mmol·min))、对Sb吸附虽弱但快(q_e=0.19 mmol/kg,k_2=0.076 9 kg/(mmol·min));高岭土对P吸附强更快(q_e=0.66 mmol/kg,k_2=0.591 kg/(mmol·min))、对Sb吸附虽强但慢q_e=0.39 mmol/kg,k_2=0.052 4 kg/(mmol·min)]。因此,Sb对P吸附的抑制在膨润土上更明显(主要是静电吸附竞争),P对Sb吸附的抑制则在高岭土上更突出(主要是配位吸附竞争)。

Competition Adsorption of Antimony (Sb) and Phosphorus (P) on Bentonite and Kaolinite

The competition adsorption isotherms and kinetics of antimony (Sb) and phosphorus (P) on bentonite and kaolinite were investigated by bath methods; the effects of pH on their competition adsorption were also studied. The results showed that the adsorption of Sb and P was fitted to Langmuir or Freundlich equation (R2=0.9450 – 0.9983, P<0.0001), and strong competition adsorption occurred between them, where P decreased greatly Sb maximum adsorption capacity (Qmax) from 0.86 and 10.21 mmol/kg (first Sb after P addition) to 0.64 and 2.61 mmol/kg (first P after Sb addition), respectively; while Sb markedly reduced P affinity constant (K) from 1.47 and 7.47 L/mmol (first P after Sb addition) to 0.68 and 2.34 L/mmol (first Sb after P addition), respectively. The competition adsorption of Sb and P depended strongly on solution pH where the adsorption generally decreased significantly with the increase of pH. The adsorption by bentonite was more dependent on pH than one by kaolinite, resulted in more electrostatic adsorption on the former and more specific adsorption on the latter, respectively. The competition adsorption of Sb and P could fit well pseudo second-order kinetic equation (R2>0.994, P<0.0001), where P adsorption on kaolinite was stronger and rapider (qe=0.66 mmol/kg,k2=0.591 kg/(mmol·min)) than that on bentonite (qe=0.36 mmol/kg,k2=0.0646 kg/(mmol·min)); Sb adsorption on the former was stronger and slower (qe=0.39 mmol/kg,k2=0.0524 kg/(mmol·min)) than that on the latter (qe=0.19 mmol/kg,k2=0.0769 kg/(mmol·min)). So, there was more Sb inhibition for P adsorption on bentonite (mainly a competition between electrostatic adsorption), and more P inhibition for Sb adsorption on kaolinite (mainly a competition between ligand adsorption).