Development and evaluation of amine-functionalized β-cyclodextrin grafted starch as a natural flocculant for turbidity removal in water treatment

• Published in: International journal of biological macromolecules 2024-11, Vol.280 (Pt 4), p.136118, Article 136118
• Main Authors: Salehin, Moghadaseh, Khoshbouy, Reza, Fatehifar, Esmaeil
• Format: Article
• Language: English
• Subjects: Amines - chemistry; beta-Cyclodextrins - chemistry; Bio-flocculation; Flocculation; Hydrogen-Ion Concentration; Kaolin - chemistry; Kaolin suspension; Starch - chemistry; Starch-based flocculant; Turbidity removal; Wastewater - chemistry; Water Purification - methods; β-Cyclodextrin modified starch
• ISSN: 0141-8130; 1879-0003; 1879-0003
• DOI: 10.1016/j.ijbiomac.2024.136118

Recently, biopolymers have been used as coagulants/flocculants due to their biodegradability, low cost, and renewability. In this study, an environmentally friendly amine-functionalized starch-based flocculant was successfully prepared. Initially, β-cyclodextrin was grafted onto the starch backbone to increase the number of hydroxyl groups, and this composite was named CD-starch. Subsequently, in order to introduce cationic properties and enhance effective flocculation, CD-starch was modified using amine functional groups. The surface functional groups were engineered by introducing different amine to CD-starch ratios (0.5:1, 1:1, 2:1 w/w), named A-CD-starch 0.5, 1 and 2, respectively. Following the characterization of the synthesized substrate, its performance in the flocculation process of a kaolin suspension was investigated. The effects of different parameters, including pH, flocculant dosage, and initial turbidity on wastewater turbidity removal, was investigated. The results showed that a higher ratio of amine to CD-starch leads to a better amination reaction due to the greater availability of nitrogen for alkylation. Jar experiments showed that for initial turbidities of 50, 150 and 300 NTU, the appropriate doses of flocculant were 0.070, 0.085 and 0.130 mg/mL, respectively. For these initial turbidities, the maximum turbidity removal was achieved 80.1 %, 92 %, and 97.8 %, respectively. This work provides an innovative natural flocculant based on starch which can effectively treat turbid wastewaters. [Display omitted] •β-Cyclodextrin was covalently attached to starch by esterification.•An enhanced flocculation was achieved by cationic functionalization of CD-starch.•This flocculant effectively removed turbidity from water in a broad range of pH values.•The efficiency of this flocculant in flocculation of kaolin suspension is near 100 %.•The effectiveness of this enhanced flocculation process was validated through the treatment of a real wastewater.