α-FeO and polypyrrole impregnated alginate/gelatin nanocatalysts for the reduction of azo dyes and persistent organic pollutants.

Herein, we propose magnetic nanocomposites as a powerful new catalyst for organic pollutant reduction. Polypyrrole (PPy) was synthesized in situ within the semi-interpenetrating alginate (Alg)/gelatin (Ge) network in presence of α-FeO as encapsulating matrix and inorganic filler, respectively. The polymeric matrix can act as bifunctional agent such as a binder and stabilizer to improve nanocatalyst stability while preserving their catalytic/magnetic performances. The results showed that Alg/Ge/PPy/FeO catalyst was more effective than its Alg/Ge/PPy and Alg/Ge/PPy/FeO homologues, suggesting a synergistic effect between PPy and α-FeO for efficient pollutant removal. Nevertheless, despite the fact that the nanocatalysts showed good catalytic activity for all selected organic pollutants, a selectivity was observed in the following order: methyl orange (MO) > direct red 16 > congo red>amoxicillin>ciprofloxacin>acetamiprid with a rate constant k of 0.54 min-1 achieved for MO reduction over Alg/Ge/PPy/FeO. The proposed mechanism for MO reduction based on HPLC-Q-TOF analysis supports the rupture of azo bond through hydrogenation. Moreover, magnetic nanocatalysts were easily recovered and reused without apparent loss of catalytic activity up to six successive cycles (89 %), and under different mineral salt samples. Lastly, the advantage of the optimized catalyst lies in its reduced manufacturing cost compared with those based on gold, platinum or silver.