Removal of Lead Ions From Aqueous Solutions Using Melamine-Modified Nano Graphene Oxide

Today, due to the industrialization of societies, the existence of heavy metals has created many problems for humans, other organisms, and the environment. Lead (Pb) is highly toxic and the second most commonly used metal. The aim of this study was to evaluate the efficiency of melamine-modified nanographene oxide in the removal of Pb from aqueous media. To increase the efficiency of graphene oxide, it was mechanically converted to nano graphene oxide and melamine (۴, ۲ and ۶-triazine, ۳, ۱ and ۵ triamine). Experiments were performed at pH value of ۳-۸, temperature of ۱۵-۵۰°C, Pb concentration of ۵-۲۰۰ mg/g, adsorbent dose of ۰.۰۱-۰.۰۶ g, and contact time of ۱۵-۱۵۰ minutes. The mechanism of the adsorption process was investigated using two Langmuir and Freundlich isotherm models, pseudo-first order and pseudo-second order kinetic equations, and thermodynamic equations. The results showed that the adsorption rate corresponds to the Freundlich isotherm model and pseudo-second order kinetic equation. Thermodynamic studies also showed that the adsorption process is associated with increasing irregularities and it is endothermic. In constant conditions (pH of ۶, contact time of ۶۰ minutes, ambient temperature of ۲۲°C, Pb concentration of ۲۰ mg/L, and adsorbent dose of ۰.۰۱ g), the adsorption capacity was ۱۹۱.۶۵ mg/g. The highest adsorption occurs at the concentration of ۵ mg/L and the highest adsorption capacity and removal percentage was observed at a concentration of ۲۰۰ mg/L, which were ۱۸۹۶.۳ mg/g and ۹۸.۸%, respectively. Due to the high adsorption capacity, the adsorbent was able to remove lead from the contaminated environment.