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). FTIR, SEM, and EDAX were used to characterize the chitosan derivatives before and after the removal of metals. The experiments were designed with the central composite design (CCD) of response surface methodology (RSM). The metal ion removal experiments were conducted as per the statistical design to determine the optimum process conditions; initial pH of the feed solution, polymer to metal loading ratio (P/M), and initial concentration of the feed solution. The optimization study was conducted to maximize the heavy metal rejection and binding capacity of the chitosan derivatives. The analysis of variance (ANOVA) was performed to validate the developed regression models.