Many protein-based biomaterials, such as waste hair and feathers, can absorb heavy metal ions from wastewater. It has been observed that metal uptake by these materials increases in alkaline condition. The enhanced uptake in alkaline conditions is due to

A

generation of many ligand sites in the protein molecules due to removal of $$\text{H}^+$$

B

availability of a high concentration of $$\text{OH}^-$$ ions as ligands

C

increased cross-linkages in the protein chains by formation of amide bonds

D

increase in solubility of the proteins