Removal of Pb(II) from aqueous solution by cross-linked starch phosphate carbamate

The adsorption process of Pb(II) ions from aqueous solution by water-insoluble starch phosphate carbarnates was investigated. The influences of adsorption conditions, such as adsorption time, adsorbent dose, pH, content of the substituent groups, initial Pb(II) concentration, and temperature, were thoroughly studied. It was shown that an adsorption time of 20 min is sufficient to reach the adsorption equilibrium, the adsorption equilibrium data follow well the Langmuir isotherm model, and the adsorption of Pb(II) ions on cross-linked starch phosphate carbamate is endothermic in nature. For the cross-linked starch phosphate carbamate (CSPC3) with a phosphate group content of 3.10 mmol/g and a carbamate group content of 1.40 mmol/g, the maximum adsorption capacity evaluated from the Langmuir isotherm towards Pb(II) is 2.01 mmol/g. In addition, repeated adsorption/desorption cycles were performed to examine the reusability of adsorbents and the recovery efficiency of Pb(II) ions. The adsorption capacity of Pb(II) ions by CSPC3 decreased from 1.85 to 1.47 mmol/g for three cycles.