Preparation of MXene and functionalization with nickel single and dual-atom with sodium alginate framework for advanced photocatalytic eradication of pollutants in wastewater

Nickel single/dual atoms anchored on MXene boost photocatalytic efficiency. • SA hydrogel framework enhances charge transfer and structural stability. • 97.8% RhB and 88% TCH degradation achieved under visible light. • Strong pH tolerance and adaptability across diverse wastewater conditions. • Excellent recyclability with ∼78% RhB efficiency retained after 10 cycles. The development of efficient, stable, and recyclable photocatalysts is essential for the remediation of complex wastewater pollutants. Herein, an advanced MXene@Ni₁/Ni₂-SA hydrogel was constructed by anchoring atomically dispersed nickel single-atom (Ni₁) and dual-atom (Ni₂) active sites onto conductive MXene nanosheets and immobilizing them within a sodium alginate (SA) three-dimensional framework. This rational design integrates high electrical conductivity, abundant active sites, and structural durability, enabling superior visible-light-driven photocatalytic performance. The MXene@Ni₁/Ni₂-SA hydrogel exhibits excellent activity toward rhodamine B (RhB) and tetracycline hydrochloride (TCH). For RhB, degradation efficiencies exceeded 97.8% under optimal conditions and remained above 90% across pH 2–8, hydrogel dosages of 1–4 g, and initial dye concentrations ranging from 30 to 100 mg L −1 . For TCH, a maximum removal of 88% was achieved at 10 mg L −1 , with >75% degradation maintained even at 30 mg L −1 across a broad pH range (2−12). Kinetic studies revealed high apparent rate constants of 0.063 min −1 and 0.0230 min −1 for RhB and TCH. Reactive species quenching and EPR spectroscopic analyses confirmed that •OH and •O₂ − radicals dominate the degradation pathways, facilitated by efficient charge separation at the Ni atomic sites–MXene interface. The hydrogel demonstrated strong recyclability, retaining ∼78.4% and ∼ 60.0% of its initial activity toward RhB and TCH after ten cycles. This work demonstrates a scalable and structurally robust MXene-based single/dual-atom hydrogel platform with significant potential for practical wastewater treatment. The findings provide new insights into atomically engineered photocatalysts for efficient and sustainable environmental remediation.