Facile fabrication of high capacity citric acid cross-linked chitosan and carboxymethyl cellulose-based hydrogel for fast kinetics removal of Cu(II)

Adsorption is the most efficient technique for the removal of toxic organic dyes and metal ions from wastewater and it demands efficient, low-cost, environment friendly and collectable adsorbents. In this study, a one-pot strategy has been developed for the crosslinking of chitosan and carboxymethyl cellulose with citric acid to form the cross-linked hydrogel. The synthesized biosorbent hydrogel was characterized by FTIR, XRD and SEM that have confirmed the successful crosslinking. The batch adsorption experiments were performed to examine the capacity of hydrogel for the adsorption of Cu(II). The optimization of the adsorption process was carried out on the basis of various factors including; metal ion concentration, time, temperature, pH, agitation speed and adsorbent dose. Different isothermal and kinetic models were applied to interpret the data. The thermodynamic studies revealed that Langmuir model was the best fit with > 90% Cu(II) removal at pH 6. The kinetic studies confirmed the suitability of pseudo-second-order kinetics with correlation coefficient (R²) value 1. Several adsorption–desorption cycles were performed to check the recovery and reusability of hydrogel without the loss of maximum adsorption capacity.