Water contamination by arsenic(V) [As(V)] and Congo red (CR) dye poses concurrent threats to public health and aquatic ecosystems, particularly in regions where metallurgical and textile industries coexist. Developing a single adsorbent capable of simultaneously addressing these chemically distinct pollutants, while recovering value from the spent material remains an open challenge in sustainable water treatment. This study reports the synthesis and evaluation of a novel ternary MgZnFe-LDH/1,2,4-triazole composite (TM-LDH/TZ), engineered for the concurrent adsorptive removal of As(V) and CR, and the subsequent repurposing of the pollutant-loaded material as an electrocatalyst for the urea oxidation reaction (UOR). The composite was prepared via co-precipitation and triazole surface grafting, then characterized by FTIR, XRD, BET, TGA, FESEM, and HRTEM. Batch adsorption experiments examined the influence of pH, adsorbent dose, initial concentration, and temperature, with equilibrium data modeled through Langmuir, Freundlich, Temkin, and the statistically grounded Advanced Monolayer Model (AMM); kinetics were assessed using pseudo-first/second-order and Elovich models. Maximum Langmuir adsorption capacities reached 204.75 mg g⁻¹ for As(V) and 499.72 mg g⁻¹ for CR simultaneously at pH 5 and 25 °C, surpassing the majority of previously reported single-pollutant adsorbents. Elovich and pseudo-second-order kinetics confirmed chemisorption as the governing pathway for As(V) and CR, respectively, while AMM thermodynamic analysis verified spontaneous adsorption across all experimental conditions. The spent composite delivered a UOR peak current density of 184.67 mA cm⁻² that is nearly twice that of the fresh material, with a reduced charge-transfer resistance of 1.19 Ω, and removal efficiency remained above 85% through three successive regeneration cycles. The bifunctional design, coupling high-capacity dual-pollutant removal with catalytic valorization of waste, positions TM-LDH/TZ as a circular-economy-aligned platform for advanced water remediation.

Colorectal cancer (CRC) presents a significant global health challenge, where the efficacy of conventional treatments is often hampered by systemic toxicity, poor bioavailability, and drug resistance. Drug repurposing and nanotechnology offer promising avenues to overcome these limitations. While pH-responsive Eudragit S100–chitosan hybrid systems are established as robust pH-responsive oral delivery carriers, the present study introduces a novel therapeutic strategy by combining these platforms with the co-delivery of the repurposed drugs pentoxifylline (PTX) and simvastatin (SIM) for synergistic CRC therapy. A hybrid nanoparticle system was synthesized using ionic gelation, combining the mucoadhesive properties of chitosan with the pH-dependent release of Eudragit S100. The formulation was optimized using a Quality by Design (QbD) Box–Behnken design to yield nanoparticles with a particle size of 152 ± 5 nm, a zeta potential of +31.2 ± 1.5 mV, and high entrapment efficiency for both drugs (PTX: 85.4 ± 3.1%; SIM: 78.9 ± 2.8%). In vitro release studies in simulated gastrointestinal media demonstrated minimal drug release in acidic conditions (PTX <8.3%; SIM <5.7%) and sustained release at colonic pH (cumulative release: PTX 82.3 ± 3.7%, SIM 78.6 ± 3.2% at 24 h; plateau levels of 89.7% and 85.4% by 48 h), confirming the pH-responsive release behavior of the formulation, with preferential drug liberation at neutral-to-alkaline pH conditions mimicking the colonic environment. These in vitro findings demonstrate pH-triggered release characteristics consistent with a mechanistic rationale for preferential colonic drug exposure; however, in vivo validation is required to confirm whether site-specific delivery to the colon is achieved under physiological conditions. Molecular docking simulations revealed strong binding affinities of simvastatin against key cancer targets EGFR, CA9, and GSK3β (ΔG: −7.5 to −8.7 kcal mol⁻¹), providing a mechanistic rationale for its repurposing. The optimized nanoformulation (NP-PTX/SIM) exhibited significant synergistic anti-proliferative cytotoxic effects against HCT-116 cells (IC₅₀ = 10.21 µg mL⁻¹) compared to free drugs through caspase-3 activation and suppression of proliferative (Ki-67) and angiogenic vascular endothelial growth factor (VEGF) markers confirming its apoptotic effects. By integrating the established Eudragit S100–chitosan carrier with the novel co-delivery of pentoxifylline and simvastatin, coupled with QbD optimization and comprehensive therapeutic evaluation, this work presents a distinct and innovative multi-targeted therapeutic strategy for CRC with improved efficacy and reduced off-target effects.