Removal of heavy metals from wastewaters using an effective and natural bionanopolymer based on Schiff base chitosan/graphene oxide

Abstract

The nanochitosan was extracted from shrimp wastes and modified by Schiff base ligand and graphene oxide. Nanochitosan characterization was carried out by Fourier-transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and elemental analysis. This study was done to apply nanopolymer based on shrimp wastes as a biodegradable and recoverable biosorbent for removal of heavy of metals including copper and lead from contaminated water. The effects of initial solution pH, biosorbent dose, initial concentrations of lead(II) and copper(II) and contact time on the uptake capacity of the related metals were investigated using batch experiments. This nanopolymer biomass exhibited the highest uptake capacity for the metal ions (466 and 698.8 mg/g for lead and copper ions, respectively) at the pH value of 6.0, the biomass dose of 0.01 g/L, the metal concentration of 200 mg/L and the contact time of 420 min. These remarkable uptake capacity values indicate the high efficiency of the absorbent in wastewater treatment for heavy metals. Its structural stability and efficient absorbent ability were proved after four times absorption–desorption cycles. After these times, the uptake capacity decreased from 698.8 to 343.8 for copper and from 466 to 226.9 for lead, which are still high values for uptake capacity, and therefore this nanopolymer can be used in repeated absorption–desorption cycles. This nanochitosan is able to treat and absorb lead and copper from dense aqueous solutions with low amount of biosorbent.