Upcycling of Agro-Industrial Waste into Functional Biochars for Methylene Blue Removal

Lim, Ivan Zhe Lam (2025) Upcycling of Agro-Industrial Waste into Functional Biochars for Methylene Blue Removal. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

MB, a cationic synthetic dye, is commonly found in the paper, cotton, textile, and pharmaceutical industries. MB is toxic and carcinogenic and its release into surface water could cause serious environmental pollution. In this study, MB removal was achieved by upcycling DSMW and corresponding composites through co-pyrolysis with (1) SA and (2) ESEMW. DSMW infused with 1% SA produce a biochar with high porosity which adsorbed 99.7% of 5 mg/L MB in 60 minutes. The removal of MB via mere adsorption in biochars, ensued by direct disposal, however may lead to secondary pollution. Thus, the DSMW was further co-pyrolysed with a second agro-waste comprising ESEMW. This unique combination allowed upcycling of two agro-waste simultaneously, producing a new biochar composed of Ca(OH)2 distributed across a carbon network made of pyrolysed EM and DSMW. This allowed the adsorbed MB to be photocatalytically degraded under UVC light due to the matching of Ca(OH)2’s band gap (4.2 eV) and UVC’s photon energy (4.8 eV). The composite could be further functionalised via the incorporation of Fe3O4 to produce a new Ca(OH)2/C/Fe3O4 composite biochar. The Fe3O4 imparted superparamagnetic property to the biochar and enhanced the rate of photocatalytic degradation of MB by trapping and preventing recombination of electron-hole pairs generated in Ca(OH)2. Biochars fabricated were characterised using FESEM, EDX, TOC, FTIR, zeta potential and VSM. The Ca(OH)2/C/Fe3O4 composite biochar performed best with 99.9% of 5 mg/L MB being degraded under just 120 minutes of UVC light radiation. The upcycling work here has the potential to be offered as an effective route for dye remediation while supporting the SDGs (6, 12, 13, 14) and ESG by transforming agro-waste into high-value and eco-friendly materials.