Removal of pollutants from aquaculture wastewater using chitosan/bentonite composite beads

Abstract

Aquaculture systems produce ammonia nitrogen as a by-product of aquatic animal protein metabolism. The dropwise method was used in this study to prepare composite beads based on the chitosan (CS) biopolymer and bentonite (Bt) clay to remove ammonia nitrogen from aquaculture wastewater. The composite beads were characterised using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis and environmental scanning electron microscopy. According to the FTIR analysis, CS was successfully immobilised on the surface of Bt. Furthermore, the XPS analysis revealed that the chemical surface of the chitosan/bentonite (CSBt) composite was rich in CS elements. To remove ammonia nitrogen, three samples of aquaculture effluents were collected and characterised in terms of physico-chemical and chemical aspects. The ammonia nitrogen removal from aquaculture effluents was 100, 91.8 and 87.7% for initial concentrations of 0.56, 1.72 and 2.13 mg/l, respectively. Ammonia nitrogen sorption tends to reach equilibrium in approximately 120 min. The findings also show that the kinetic data correlated well with the pseudo-second-order equation. pH values increased slightly after adsorption, and the same trend was observed for total hardness and alkalinity. As a result, the CSBt composite is a promising adsorbent for ammonia nitrogen removal from aquaculture effluents.