Removal and recovery of heavy metals through size enhanced ultrafiltration using chitosan derivatives and optimization with response surface modeling.

N‑N‑N‑triethylammonium chitosan (TEAC) and carboxymethyl chitosan (CMCh), the two water-soluble chitosan derivatives were utilized for the removal and recovery of heavy metals by size enhanced ultrafiltration (SEUF). The strong positive quaternary ammonium [-N(CH)] cation in TEAC interacts with Cr(VI), which exists as a strong chromate anion thereby enabling the efficient removal of chromate through ultrafiltration. CMCh consists of COOH and NH moieties, which facilitate interactions with heavy metals such as Cu(II) and Ni(II).