New method for hydrogel synthesis from diphenylcarbazide chitosan for selective copper removal

In this work, a simple method was developed for hydrogel preparation from 1,5-Diphenylcarbazide (DPC) and chitosan (CS) through Diazotization reaction of CS as a selective adsorbent (DPCCS) for Cu(II) ions. CS was treated with sodium nitrate and subsequent crosslinking reaction with DPC for the preparation of DPCCS. Different techniques were used for characterization of DPCCS. Various parameters such as, temperature, pH, and concentration of Cu(II) were used for adsorption studies. Kinetics of Cu(II) ion on DPCCS follows the Pseudo second order and equilibrium of adsorption occurs in short time. The equilibrium data was best fitted with the Langmuir isotherm and the maximum adsorption capacity of DPCCS was 185.505 mg g⁻¹. Thermodynamic parameters ΔG°, ΔH° and ΔS° suggested that the adsorption of Cu(II) ion on the surfaces of DPCCS was spontaneous, endothermic and randomness of Cu(II) ion in the solution was enhanced respectively. Regeneration of DPCCS and Cu(II) ion recovery were studied up to five cycles without the lost of the adsorption capacity.