Influence of initial copper concentration, pH, and cross-linked alginate-chitosan and alginate-chitosan-Aspergillus australensis composite beads on the adsorption capacity and removal efficiency of copper ions

Copper (Cu) is a toxic heavy metal whose concentration must be reduced to values under the environmental standard before discharges can be released into the environment. Due to its characteristics, using different adsorbents for biosorption is a convenient method for removing heavy metals. Alginate and chitosan are biopolymers that have shown high potential as adsorbents. This investigation discusses the influence of pH, initial concentration of copper (Co), and the type of immobilized bead in the adsorption capacity and removal efficiency of copper from synthetic solutions. FT-IR analysis showed cross-linked composite beads of alginate-chitosan (ICB) and alginate-chitosan-Aspergillus australensis (IBB) possess different functional groups. The analysis made with the kinetic models showed that the adsorption mechanism was governed by diffusion through interface and chemical adsorption. Adsorption capacity depends on pH and Co. Maximum average adsorption capacity was 4.46 mg/g at 600 mg/L and pH 4.5 for ICB. Statistical analysis demonstrated that Co, pH, and their interactions significantly affect removal efficiency. Besides, the highest removal efficiency was 36.18\% $\pm$ 1.87 at pH 4.5, 150 mg/L for IBB. These biomaterials could be a potential adsorbent for removing copper from wastewater.

Keywords: copper, chitosan, alginate, cross-linked composite beads, adsorption.