Metal sericin complexation and ultrafiltration of heavy metals from aqueous solution

• Metal-sericin complexation in ultrafiltration study was discussed.
• Effect of metal concentration and sericin dose on R% and J was evaluated.
• Role of anions in ultrafiltration study of metal ions of salt pairs was elaborated.
• Kinetic and pH study of metal removal from aqueous solution was made.

This work exclusively confers theoretical insight into ultrafiltration of heavy metal ions (Pb2+, Co2+, Ni2+, Cu2+, Zn2+) from aqueous solution using sericin biopolymer. Sericin is a water soluble bio-macromolecule and has potential to show chemical interaction with metal ions due to protein units containing several amino acids. The functional groups of sericin such as amine (NH2), disulfide linkage (SS) and carboxylic acid (COOH) assign it role of poly dentate ligand (PDL). Provision of negatively charged surface with lone pair of electrons facilitates metal-sericin complexation owing to d-electron deficient metal ions. Sericin-chelated metal ions are retained by pores of membrane when the aqueous solution is subjected to pass through membrane on account of their enhanced size. Metal trapping efficiency of sericin was measured by determining rejection percentage (R%) and permeate flux (J) at three different trans-membrane pressures (TMP) during ultrafiltration study. More importantly, effect of anions was evaluated by comparing two different salts of same metal ion. High formula weight and greater solubility of salts leave significant impact on R% and J. Greater contact time between metals and sericin enhanced R% followed by reciprocal trend of J in batch experiment. In addition, basic pH helps to increase R% values of metal ions in sericin supported ultrafiltration study.

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