Preparation of cationic chitosan-polyacrylamide flocculant and its properties in wastewater treatment

Abstract

Chitosan derived from crab shells, was used to prepare the graft polymer in aqueous solution with acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC) as raw materials and ceric ammonium nitrate (CAN) as initiator. The flocculation ability of the resulting polymer (PCAD) was studied in waste water treatment experiments. Its properties were determined on the basis of the transmittance of waste water after flocculation. The effects of chitosan and DMC content on PCAD's flocculation ability were studied. Flocculation experiments were also undertaken under various pH conditions. According to the experimental data, the flocculation ability could be improved when chitosan content decreased in the raw material, but the monomer conversion would decrease obviously. When the chitosan's content was more than 65%, AM and DMC groups were less on each chitosan molecule. So PCAD's flocculation ability was poor. Similarly, high content of DMC would result in low monomer conversion and high flocculation ability. PCAD molecules with more DMC group had more positive charges. It was favorable to flocculation. However, monomer conversion would decrease with the increase of DMC content. The suitable conditions were that chitosan and DMC contents were 65% and 15-20%, respectively. The experiment data showed that PCAD had good flocculation ability under weak acidic condition. Its ability would be weakened by strong acidic or alkaline condition. The flocculation efficiency was the best at pH of 5.5 when PCAD's dosage was 8mg⋅L -1 . Compared with cationic polymer (the copolymer of AM and DMC, PAD), PCAD showed better flocculation ability under acid and neutral conditions, but worse ability under alkaline condition.

Recent Achievements in Polymer Bio-Based Flocculants for Water Treatment

“…Applications of copolymers of grafted chitosan are increasingly proposed in the wastewater treatment process [ 5 , 27 , 38 ]. Based on the assumption that flocculation properties can be improved by introduction of functional groups into macromolecule structure, Wang et al [ 90 ] synthesized a series of graft chitosan flocculants. They demonstrated that high content of methacrylate ethyl trimethyl ammonium chloride (DMC) groups results in better flocculation ability than acrylamide grafted polymer.…”

The Use of Chitosan and Starch-Based Flocculants for Filter Backwash Water Treatment

“…It is a linear copolymer of D-glucosamine and N-acetyl-d-glucosamine ( Figure 2 a) [ 7 ]. Grafted chitosan copolymers are recommended as an eco-friendly flocculant for water and wastewater treatment with acrylamide [ 17 , 25 , 26 , 27 ]. Moreover, chitosan and its derivatives are known for their biocidal properties, valuable in biomedical applications.…”

Biodegradation of water‐soluble and water‐dispersible polymers for agricultural, consumer, and industrial applications—Challenges and opportunities for sustainable materials solutions

“…An increase in solution transmittance from 90% to 95% of treated and settled wastewater was demonstrated at flocculant concentrations between 5 and 20 mg per liter at a pH below 7. 81 Chitosan can also be modified to obtain an anionic biobased flocculant. As an example, Sun et al modified chitosan with xanthate and sulfonic acid groups.…”

“…This is done by adding flocculant to, for example, a wastewater sample and then comparing the clarity of the aqueous solutions after sedimentation. An increase in solution transmittance from 90% to 95% of treated and settled wastewater was demonstrated at flocculant concentrations between 5 and 20 mg per liter at a pH below 7 81 . Chitosan can also be modified to obtain an anionic bio‐based flocculant.…”