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. [Display omitted] •The ratio of adsorption sites to Cr (Ⅵ) is crucial for ensuring the removal rate.•Increasing the adsorbent dosage can effectively counteract environmental factors.•The maximum adsorption capacity of Cr(Ⅵ) by Poly (AM-co-DMC) is 135.32 mg/g.•The Poly(AM-co-DMC) discoloration indicates the need to replace the adsorbent.