Evaluation of a granular Cu-modified chitosan biocomposite for sustainable sulfate removal from aqueous media: A batch and fixed-bed column study

Adsorption-based treatment of sulfate contaminated water sources present challenges due to its favourable hydration characteristics. Herein, a copper-modified granular chitosan-based biocomposite (CHP-Cu) was prepared and characterized for its sulfate adsorption properties at neutral pH via batch equilibrium and fixed-bed column studies. The CHP-Cu adsorbent was characterized by complementary methods: spectroscopy (IR, Raman, X-ray photoelectron), thermal gravimetry analysis (TGA) and pH-based surface charge analysis. Sulfate adsorption at pH 7.2 with CHP-Cu follows the Sips isotherm model with a maximum adsorption capacity (407 mg/g) that exceeds most reported values of granular biosorbents at similar conditions. For the dynamic adsorption study, initial sulfate concentration, bed height, and flow rate were influential parameters governing sulfate adsorption. The Thomas and Yoon-Nelson models yield a sulfate adsorption capacity (146 mg/g) for the fixed bed system at optimized conditions. CHP-Cu was regenerated over 5 cycles (33 % to 31 %) with negligible Cu-leaching. The adsorbent also displays excellent sulfate uptake properties, regenerability, and sustainable adsorbent properties for effective point-of-use sulfate remediation in aqueous media near neutral pH (7.2). This sulfate remediation strategy is proposed for other oxyanion systems relevant to contaminated environmental surface and groundwater resources.