Brown Algal Residue for the Recovery of Metal Ions—Application to La(III), Cd(II), and Ni(II) Sorption

Abstract

metals are frequently found in the wastewater of many industries such as mining, foundry, electroplating (coating and protective treatments), surface finishing, battery manufacturing. Other strategic elements, such as rare earth elements (REEs) [3] (or noble metals [4] ) are also discharged into the environment through industrial wastewater, also joining the food chain as they are not biodegradable. Increasingly strict legislation, together with the sustainability objectives proposed by the United Nations as well as proactive policies, make new waste recycling processes necessary to save resources and achieve sustainable development. Cadmium is mainly used in batteries (about 80% of production); another common use of this metal protective compound concerns electroplate steel (especially for aircrafts and oil platforms). Less developed application concerns the control of atomic fission in nuclear reactors (for neutron absorption). [5] Therefore, removing this metal from wastewater is of crucial importance. Along with Cd, other heavy metals such as Ni, Hg, Zn, Cu, Pb, or Cr are often found in wastewater; [1a] therefore, nickel may be another interesting tracer of metal contamination for developing alternative sorption processes. On the other hand, rare earths are extracted from their ores (after leaching step) by ion exchange and solvent extraction, which generates waste streams that are harmful to the environment. [6] Rare earths have also become strategic metals in high-tech industry; 90% of the world's extraction and production is mainly controlled by China. [7] The REE supply recently became a geostrategic and political issue worldwide for industries based on energy storage, [8] and electronic devices. [9] Cadmium and nickel are frequently associated with industrial waste (such as in rechargeable Ni-Cd batteries). On the other hand, LaNi alloys are used for hydrogen storage, they are also associated in metal hybrid batteries for hybrid cars.There are many processes to recover or remove metals from wastewater streams, such as chemical precipitation, filtration membranes or ion exchange resins, among others. [1a,3a,10] However, most of these methods are generally expensive, they are not eco-friendly, they are inefficient especially at low metal concentrations, [11] and they can also generate new residues that, in turn, need to be treated. [12] Techniques such as bioremediation [13] or biosorption [14] can take advantage of the

Metal biosorption onto non-living algae: a critical review on metal recovery from wastewater

“…When aiming at metal recovery, metals are strategically selected based on their criticality, societal importance and market value. 43,[88][89][90] This approach aspires to achieve optimal sorption capacity values to ensure maximum metal preconcentration onto the sorbent resorting to minimum algae-to-metal ratios. Saturation of the algae functional groups is promoted while boosting their cost performance as metal pre-concentrators.…”

On membrane-based approaches for rare earths separation and extraction – Recent developments

“…Bearing in mind such tremendous needs for REEs, other pathways away from the exploration and mining of natural resources should be considered. The alternative options should focus on improving recycling facilities and waste collection [41] (permanent magnets (Nd), fluorescent powders, television tubes, flat panel displays) [42][43][44][45][46][47][48][49], developing novel solid or liquid extraction systems [50][51][52][53][54][55], and implementing separation and bio-separation technologies [56][57][58][59][60][61][62]. At the European level recycling process is an essential solution owing to limited options for growing the primary supply.…”