Synergistic Removal of Copper(II) and Tetracycline from Water Using an Environmentally Friendly Chitosan-Based Flocculant

Abstract

In the current work, an environmentally friendly chitosan-based flocculant (carboxyethyl chitosan, denoted as CEC) was prepared to flocculate copper(II) and tetracycline (TC) simultaneously for the first time. The effects of flocculant dosage, pH, and initial contaminant concentration were systematically studied. For a single contaminant system, CEC demonstrates the desired flocculation performance for copper(II) removal, whereas its TC removal efficiency is poor. However, it is notable to find that the removal of TC can be significantly enhanced when copper(II) coexists in the binary contaminant system. Compared to the commercial flocculants polyaluminum chloride and polyacrylamide, CEC enjoys the advantages of lower dosage requirement, higher removal efficiency, and better floc properties. The flocculation mechanism was investigated via pH monitoring, zeta potential, and floc property measurements. The results indicate that charge neutralization predominates for single contaminant copper(II) removal, while for binary contaminant removal, TC can be embedded in copper(II) hydroxides through coordination with the metal, and finally synergistically eliminated with copper(II). This work gives a new approach to treating livestock wastewater and extends the application fields of flocculation.