Polyhydroxamic acid as an efficient metal chelator and flocculant for wastewater treatment

Hydroxamic acid containing organic polymeric flocculants were synthesized from three different commercially available polymeric flocculants, such as WAS590, Zetag 4100, and Zetag 4110. These three polymers are acrylamide and acrylic acid-based copolymers with different molecular weights and anionic charge density. The conversion of the amide groups to hydroxamic acid groups in the polymers was carried out by the reaction with hydroxylamine at pH 14. The modified polymers were characterized for structure and composition by elemental analysis, FTIR, and NMR. The chelation activity of the modified polymers was determined toward iron (Fe³⁺) and copper (Cu²⁺). The flocculation activity of the non-modified and modified polymers was evaluated toward produced water and scrubber water. The results showed that all the modified flocculants exhibit better chelation with Fe³⁺ and Cu²⁺. In addition, the modified polymers display improved flocculation effect on tested wastewater.