Chitosan biopolymer membranes produced from fishery waste for the adsorption-based removal of lead ions from aqueous systems

Abstract

Using a phase inversion technique, chitosan was recovered from the exoskeleton of Cape Rock Lobsters, which are common in the area around Cape Town, South Africa. These flakes were then used to create dense polymer chitosan membranes. Chitosan membrane (CSM) and cross-linked chitosan membrane (XCSM) were characterized by FTIR, XRD, SEM-EDX, and TGA after the chitosan membrane was cross-linked with 2.0% glutaraldehyde. The maximum binding capacity for the developed adsorbent (XCSM) was found to be 2.98 mmol.g-1 at temperature of 313 K. Equilibrium tests showed that the Langmuir equilibrium model could be utilized to successfully characterize lead binding onto XCSM. The adsorption process was discovered to be endothermic, with an adsorption enthalpy of 52 kJ/mol. As the flux through XCSM increases, the degree of adsorption decreases (1.96-1.36 mmol/g) due to a kinetic process. Co-ions were also found to have an impact on the adsorption of metal ions by XCSM, with the presence of nitrates being found to limit the adsorption and sulphates being found to enhance the adsorption. Using sulphuric acid and hydrochloric acid solutions as eluants, the adsorbed lead ions were recovered. It was discovered that the first was a more efficient eluent. Consequently, a sulphuric acid solution with a pH of 3 might be used to recover up to 95% of the adsorbed lead. But after regeneration, it was discovered that the adsorption capacity had been diminished. This decrease in adsorption capability may be attributed to the membrane losing up to 26% of its bulk during regeneration. After two regeneration cycles, the membrane's structural integrity had been compromised, rendering it useless.

Keywords

• cross-linked chitosan membrane
• lead binding
• breakthrough curves
• binding capacity
• metal desorption