PAD resin: An intelligent adsorbent for solving Cr(VI) pollution with real-time feedback and high efficiency

To address the urgent issue of Cr(VI) pollution and protect aquatic ecosystems, we conducted an exhaustive investigation into a Poly(acrylamide-co-methacryloyloxyethyl trimethylammonium chloride) (PAD) resin synthesized through an environmentally friendly aqueous polymerization process. This resin not only boasts a high capacity for Cr(VI) removal but also incorporates a colorimetric sensing mechanism that visually transitions from transparent to yellow upon Cr(VI) adsorption, offering real-time, non-invasive monitoring and optimization of the remediation process. According to the Langmuir model, at a pH of 4.78 and a temperature of 15 ℃, the maximum adsorption capacity of PAD for Cr (VI) is 135.32 mg/g. Its adsorption kinetics conform to a pseudo-first-order model and Langmuir isotherm, indicating uniform adsorption sites and favorable interactions. Thermodynamic analysis further reveals the spontaneous and exothermic nature of the adsorption process, making it suitable for large-scale applications at ambient temperatures.In natural lake water-based Cr(VI) simulated wastewater, PAD resin achieved a remarkable removal efficiency of 99.54 % for 4.82 mg/L Cr(VI) （The filling column had a diameter of 3 cm and a height of 30 cm; The PAD dosage was 1.6 g, with a flow rate of 5 mL/min and an adsorption time of 60 min, at a neutral pH）, effectively reducing residual Cr(VI) concentrations to 0.022 mg/L, well under WHO limits (0.05 mg/L). Additionally, its 93.68 % capacity retention after four HCl regeneration cycles underscores economic feasibility & sustainability.In summary, PAD resin stands out as an innovative, high-performance, and intelligent Cr(VI) adsorbent that transcends the limitations of traditional adsorbents.