Impact of contact time, pH, ionic strength, soil humic substances, and temperature on the uptake of Pb(II) onto graphene oxide

The uptake of Pb(II) from wastewaters onto graphene oxide was studied as a function of various water quality parameters. The results indicated that uptake was fast and kinetic uptake could be well fitted by a pseudo-second-order model. The uptake was strongly dependent on pH and independent of ionic strength. Namely, inner-sphere surface complexation was the main uptake mechanism. The presence of humic acid or fulvic acid enhanced the uptake at low pH values, while reduced at high pH. The Langmuir, Freundlich, and Dubinin-Redushkevich (D-R) isotherm models were used to simulate the uptake. Thermodynamics indicated that the uptake was endothermic and spontaneous.