Metal-organic frameworks (MOFs) are currently recognized as unique platforms for environmental studies. This study evaluated the potential of nine MOFs from ZIF-8, ZIF-67, and UIO-66 families for the removal of ciprofloxacin (CIP), a toxic, bio-accumulative, and persistent fluoroquinolone antibiotic. ZIF-67-SO₄, with a rhombic crystalline morphology and 1375 m²/g BET surface area, has the highest CIP adsorption efficiency among the studied MOFs. The mathematical sorption model predicted that the highest CIP removal (99.2%) occurs when adsorbent dose, pH, and agitation time are adjusted to 6.82, 832.4 mg/L, and 39.95 min, respectively. Further studies revealed that the CIP adsorbed onto ZIF-67-SO₄ in monolayer (q_max: 2537.5 mg/g) and chemisorption controlled the rate of the process. Mass transfer kinetic coefficients improved significantly by sonication at 35 KHz in comparison with mechanical agitation. Thermodynamic parameters (minus signs of ∆G° [7.8 to 14.2], positive signs of ∆H° (58.9 KJ/mol), and ∆S° (0.23 KJ/mol·K)) demonstrated the spontaneous, endothermic, and chemical sorption of CIP. The level of cobalt leached from ZIF-67-SO₄ structure varied 1.2–4.5 mg/L, depending on pH, mixing time, and agitation type. In conclusion, the excellent adsorption properties of ZIF-67-SO₄ for CIP, made it an outstanding candidate for environmental protection purposes.

Acid red 14 (AR14) is a widely used azo dye that belongs to a major family of commercial dyes employed extensively in the textile industry. The present study aimed to investigate the photocatalytic discoloration of AR14 using a visible-light-responsive catalyst. The composite catalyst was synthesized by integrating thermally modified MIL-101 (M-MIL) integrated into bismuth oxide. Thermal modification of MIL-101 produced octahedral α-Fe₂O₃ particles with a size of 1–2 μm, which were incorporated into bismuth oxyiodide (BiOI) featuring a nanosheet structure. BiOI@M-MIL composite exhibited an enhanced photocatalytic activity. The bandgap energy, E_g, of BiOI was reduced from 1.95 eV to 1.73 eV in the composite. Photocatalytic reactions were performed under visible-light irradiation using a 5 W cold LED lamp. The AR14 discoloration tests demonstrated that BiOI@M-MIL was 1.81-fold more efficient compared to pristine BiOI. Key parameters affecting AR14 discoloration —such as catalyst dosage, pH, dye concentration, and contact time, were investigated. The composite achieved almost a complete dye removal efficiency of 94.26% under experimental conditions. Radical trapping tests highlighted the crucial role of superoxide radicals, $O_2^{.-},$ in the dye discoloration process. BiOI@M-MIL takes advantage of simultaneous adsorption and photocatalysis with the highest adsorption capacity of 45.32 mg g⁻¹ and 32.2 mg g⁻¹, based on Sips and Langmuir models, respectively. The catalyst also showed good reusability and ~14% loss in removal efficiency after five consecutive cycles. In conclusion, the BiOI@M-MIL composite demonstrates excellent photocatalytic performance, combining low energy consumption with material stability, making it a promising candidate for AR14 discoloration.

In this study, an environmentally sustainable and renewable biomass-derived from luffa agricultural waste was used as a cost-effective precursor for graphene synthesis through chemical activation and graphitization processes. Luffa-based graphene nanosheets (LGN) were synthesized and characterized using FTIR, SEM, AFM, Raman, and XRD techniques. Structural and textural analyses of the synthesized LGN confirmed the formation of a three-dimensional graphene architecture with an ultrahigh specific surface area of 2,646.3 m² g⁻¹, representing a significant increase compared to raw luffa (12.056 m² g⁻¹). Consequently, LGN achieved a high maximum adsorption capacity toward Cr(VI) of 103.73 mg g⁻¹ in water, which is approximately tenfold higher than that of the raw luffa. Optimization using Box–Behnken design predicted the optimal operating conditions at pH 2.1, adsorbent dose of 0.44 g L^-1, contact time of 44 min, and initial Cr (VI) concentration of 10 mg L^-1, with a predicted removal efficiency of 97.50%. The adsorption behavior of Cr (VI) on LGN conformed to the Freundlich isotherm and pseudo-second-order kinetics, indicating heterogeneous, multilayer adsorption dominated by strong adsorbate–adsorbent interactions. Thermodynamic analysis revealed that Cr (VI) adsorption onto LGN is spontaneous, endothermic, and diffusion-driven, with enhanced molecular mobility and reduced surface affinity at elevated temperatures. LGN maintained Cr (VI) removal efficiency over four regeneration cycles, decreasing from 94.35% to only 85.71%, confirming its structural stability and economic viability for repeated use. The findings confirm the potential of green-synthesized, biomass-derived graphene nanosheets as a sustainable and efficient adsorbent for Cr (VI) removal from aqueous environments.