Industrial effluents and wastewater treatment have been a mainstay of environmental preservation and remediation for the last decade. Silica nanoparticles (SiO₂) obtained from rice husk (RH) are an alternative to producing low-cost adsorbent and agriculture waste recovery. One adsorption challenge is facilitating the adsorbate separation and reuse cycle from aqueous medium. Thus, the present work employs SiO₂ supported on polylactic acid (PLA) nanofibers obtained by the electrospinning method for Rhodamine B (RhB) dye adsorption. The silica surface was modified with trimethylsilyl chloride (TMCS) to increase affinity towards organic compounds. As a result, the silanized surface of the silica from rice husk (RHSil) promoted an increase in dye adsorption attributed to the hydrophobic properties. The PLA fibers containing 40% SiO₂ (w w⁻¹) showed about 85–95% capacity adsorption. The pseudo-first-order kinetic model was demonstrated to be the best model for PLA:SiO₂ RHSil nanocomposites, exhibiting a 1.2956 mg g⁻¹ adsorption capacity and 0.01404 min⁻¹ kinetic constant (k₁) value. In the reuse assay, PLA:SiO₂ membranes preserved their adsorption activity after three consecutive adsorption cycles, with a value superior to 60%. Therefore, PLA:SiO₂ nanocomposites from agricultural waste are an alternative to “low-cost/low-end” treatments and can be used in traditional treatment systems to improve dye removal from contaminated waters.

Adsorption has emerged as a promising method for removing polyphenols in water remediation. This work explores chlorogenic acid (CGA) adsorption on zeolite-based magnetic nanocomposites synthesized from rice husk waste. In particular, enhanced adsorbing materials were attained using a hydrothermal zeolite precursor (Z18) synthesized from rice husk and possessing a remarkable specific surface area (217.69 m² g⁻¹). A composite material was prepared by immobilizing magnetic copper ferrite on Z18 (Z18:CuFe₂O₄) to recover the zeolite adsorbent. In addition, Z18 was modified (Z18 M) with a mixture of 3-aminopropyltriethoxysilane (APTES) and trimethylchlorosilane (TMCS) to improve the affinity towards organic compounds in the final nanocomposite system (Z18 M:CuFe₂O₄). While the unmodified composite demonstrated inconsequential CGA removal rates, Z18 M:CuFe₂O₄ could adsorb 89.35% of CGA within the first hour of operation. Z18 M:CuFe₂O₄ showed no toxicity for seed germination and achieved a mass recovery of 85% (due to a saturation magnetization of 4.1 emu g⁻¹) when an external magnetic field was applied. These results suggest that adsorbing magnetic nanocomposites are amenable to CGA polyphenol removal from wastewater. Furthermore, the reuse, revalorization, and conversion into value-added materials of agro-industrial waste may allow the opportunity to implement sustainability and work towards a circular economy.

Disposing of industrial and electronic waste poses a significant environmental challenge. A sustainable solution involves converting waste into raw materials for new components. This study synthesized the mixed oxide CoFe2O4/γ-Fe2O3@SiO2/NaAlSi3O8 using abrasive sludge from the marble and granite industry and spent lithium-ion battery cathode material. X-ray diffraction (XRD) identified LiCoO2 and graphite C in the battery cathode, while abrasive sludge contained iron (α-Fe), magnetite (Fe3O4), albite (NaAlSi3O8), mica (KAl2(AlSi3O10)(OH)2), calcite (CaCO3), and dolomite (CaMg(CO3)2). The structure and morphology of the mixed oxide revealed clusters of nanometric particles. The mixed oxide had a band gap of 3.1 eV. It was applied as a catalyst for dye degradation via the photo-Fenton process and as an electrochemical pseudocapacitor. Methylene blue (MB) decolorization reached 100% after 50 min, with pseudo-first-order kinetics (coefficient of determination (R2 ) = 0.98). This efficiency remained even after six successive decolorization cycles. Electrochemical analysis revealed a maximum capacitance of 45.50 F g–1, specific capacity of 87.26 mAh g–1, energy density of 36.41 Wh kg–1, and coulombic efficiency of 88.81%. These findings highlight its reversible pseudocapacitive profile and efficiency, underscoring its importance for sustainable development and circular economy.