Selective adsorption of Pb(II) from aqueous solution using nanosilica functionalized with diethanolamine: Equilibrium, kinetic and thermodynamic

Lead-containing wastewater comes mainly from batteries, petroleum refining, dyes, lead mine drainage and so on. Here, the nanosilica functionalized with diethanolamine (DPM-SNPs) was utilized as an adsorbent to remove lead ions from aqueous solution. TEM, SEM, XPS, FT-IR, Zeta potential and BET analyzer have been employed to characterize DPM-SNPs. The adsorption property of DPM-SNPs was studied by varying pH, reaction time, Pb(II) concentration and temperature. The selectivity, reusability and adsorption mechanism have been systematically studied. DPM-SNPs has a shorter adsorption equilibrium time (60 min) as well as a high efficiency for lead ions removal (154.38 mg/g) at 298 K. The optimized pH was 5.8, mainly due to electrostatic and chelation interactions between hydroxyl/amino groups and metal ions. DPM-SNPs showed better selectivity for Pb(II) again various interfering ions and the removal efficiency just decreased about 4% after five repeated circles. Besides, the adsorption behavior fit well to Pseudo-second-order kinetic, Langmuir and Dubinin-Radushkevich models, indicating that the chemical reaction is the rate-limiting step and the adsorption process belongs to monolayer adsorption. Thermodynamic studies revealed that the adsorption process was spontaneous, feasible and endothermic. Thus, the nanosilica functionalized with diethanolamine is a potentially effective and sustainable adsorbent for application in lead removal from wastewater.