Adsorption of indium by waste biomass of brown alga Ascophyllum nodosum

Abstract

AbstractThe biosorption capacities of dried meal and a waste product from the processing for biostimulant extract ofAscophyllum nodosumwere evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents:waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, andnatural-biomasswhich was harvested, dried and milled as a commercial, “kelp meal” product. Two systems have been evaluated:ideal systemwith indium only, anddouble metal-systemwith indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In theideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed,waste biomassand 63 mg/g for thenatural biomass), than in thedouble metal-systemwhere the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in theA. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.