Green synthesis of Co-alginate and CoNi-chitosan catalysts for catalytic reduction of organic azo dyes.

Cobalt and nickel doped catalysts were synthesized by using chitosan and alginate and used in the reduction of Remazol Yellow 4GL (RY) and Remazol Black B (RB) dyes. XRD pattern of catalysts exhibited that amorphous and semi-crystalline form for CoNi-chitosan and Co-alginate, respectively. SEM images showed catalyst's surface was rough and had grainy and rod-like structures. The surface functional groups were determined by FTIR analysis method and it was seen clearly presence of alginate and chitosan. The Co-alginate catalysts exhibited higher dye degradation (74 % for RY) and also lower reaction time (6 min for RB). The reduction reaction was in good agreement with the pseudo-first-order kinetic model and reaction rate constant was determined as 0.140 min-1 and 0.174 min-1 for RY and RB, respectively. The RY reduction percent over both catalysts was higher than RB. Co-alginate showed reduction efficiency was about 70% even after 4 runs for RY. The dye reduction capacity and catalytic activity of the catalysts were promise for organic pollutant dyes catalytic reduction applications.