Valorisation of waste rice husk into mesoporous silica for cost-effective, sustainable and efficient removal of cefuroxime from wastewater

Abstract

Pharmaceutical contaminants, such as Cefuroxime sodium, pose a significant threat to aquatic ecosystems due to their persistence and bioactivity. This study reports the synthesis of sustainable mesoporous silica adsorbents, RH-MCM-41 and RH-SBA-15, from rice husk, an abundant agricultural waste, for efficient removal of cefuroxime from water. The adsorbents exhibited points of zero charge (pH PZC ) values of 5.2 and 4.5, respectively, which influenced surface interactions with anionic cefuroxime. Batch adsorption experiments revealed high removal efficiencies, while desorption studies demonstrated that acidic eluents, particularly nitric and phosphoric acids, regenerated over 90% of the adsorbed antibiotic. In the present study, under optimum conditions (pH 6.0, adsorbent dosage 0.05 g, contact time 120 min, and initial concentration 200 mg·L⁻¹), RH-SBA-15 exhibited a maximum Langmuir adsorption capacity of 105.4 mg·g⁻¹. At the same time, RH-MCM-41 showed 98.7 mg·g⁻¹, with high cefuroxime removal efficiencies under controlled batch conditions. Reusability tests confirmed structural stability and sustained adsorption over multiple cycles. Compared with conventional adsorbents, rice husk-derived mesoporous silica combines high adsorption performance, low-cost synthesis, and environmental sustainability. These findings highlight that the synthesised mesoporous silica materials demonstrated promising adsorption performance toward cefuroxime sodium in controlled single-component model solutions, indicating their potential applicability for future pharmaceutical wastewater remediation studies.