Facile synthesis of polymer-based magnesium hydroxide nanocomposites for photocatalytic degradation for methylene blue dye and antibacterial application

• Published in: Biomass conversion and biorefinery 2023-10, Vol.13 (15), p.13539-13552
• Main Authors: Dharamalingam, Karthigaimuthu, Ramasundaram, Subramaniyan, Ponnusamy, Vinoth Kumar, Bhuvaneswari, K., Ramalingam, G., Balasankar, Athinarayanan, Jeyaram, Sriram, Pazhanivel, T., Florence, S. Sasi, Thangavel, Elangovan, Oh, Tae Hwan
• Format: Article
• Language: English
• Subjects: Biotechnology; Chemical synthesis; E coli; Energy; Light irradiation; Magnesium hydroxide; Methylene blue; Microorganisms; Nanocomposites; Original Article; Photocatalysis; Photodegradation; Polymers; Polyvinyl alcohol; Polyvinylpyrrolidone; Renewable and Green Energy; Water treatment
• ISSN: 2190-6815; 2190-6823
• DOI: 10.1007/s13399-022-02770-0

Photocatalysis has been considered as a potential technology to detoxify and clean up water contaminated with toxic chemicals and harmful microorganisms. Herein, the pure magnesium hydroxide (Mg(OH) 2 ) and Mg(OH) 2 -PVP/PVA nanocomposites were synthesized by precipitating the aqueous MgNO 3 with NaOH. Poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) were used as the polymer matrix. Formation of Mg(OH) 2 , Mg(OH) 2 -PVP, and Mg(OH) 2 -PVA nanocomposites was confirmed by the presence of X-ray diffraction peaks corresponding to Mg(OH) 2 (38.02°), PVA (21.72°), and PVP (20.15°), and the infrared peaks, OH of Mg(OH) 2 (~ 3700 cm −1 ), C–N of PVP (1650 cm −1 ), and CH 3 –CO of PVA (1098 cm −1 ). The PVP altered the morphology of Mg(OH) 2 from rice-like to circular grains; PVA resulted in flake sheet structure. PVA and PVP lowered the bandgap of Mg(OH) 2 (2.4 eV) by 0.1 eV and 0.34 eV, respectively. Under UV–visible light irradiation, Mg(OH) 2 -PVA exhibited maximum photocatalytic efficiency and degraded 93% aqueous methylene blue (20 ppm, 100 mL) within 2 h, whereas Mg(OH) 2 and Mg(OH) 2 -PVP were degraded 55% and 69%, respectively. Mg(OH) 2 -PVA exhibited stable efficiency for four reuse cycles. The antibacterial activity was assessed using Escherichia coli ( E.coli ), MTCC 443 strain. Among all, Mg(OH) 2 -PVA (100 mg/mL) exhibited the highest antibacterial activity, the zone of inhibition. Collectively, Mg(OH) 2 -PVA (18 mm) was close to a positive control (20 mm), and the minimum inhibitory concentration was 4 mg/mL. Overall, Mg(OH) 2 -PVA nanoflake was found to be an efficient and reusable UV–visible light photocatalyst for water treatment in terms of removing organic pollutants and microbial disinfection of bacteria. Graphical abstract