Chemical process of recovering cyanide as Cyanide-bridged cu(II)-co(III)/fe(III) bimetallic assemblies from preparation of semiconductors for solar cells

Safe and recyclable procedures of dispose waste KCN solution were developed forfabrication of Cu(In,Ga)Se₂ (CIGS) solar cells. Since KCN treatment is commonlycarried out on CIGS optical absorber layer to remove surplus Cu_2-xSe extra phases, thesolution contains Cu-Se. Cyanide-bridged bimetallic assemblies have been widelyinvestigated. Metal source of [M(CN)₆]^n- (M=Co(III) or Fe(III)) can be purchased andmay be thermodynamically stable except for exchange reactions in solutions. Whereas[M'L2]^m+ moieties (L = bidentate ligands; M'=Cu(II)) are easy to occur dissociation ofligands in solutions. Preparations at surface of solutions of cations and anions give rise toprecipitates of the resulting bimetallic assemblies easily. We have developed combinationof several well-known chemical reactions <1> Formation of K₃[M^III(CN)₆] (M= Co, Fe)species under basic conditions, <2> Isolation of [CuL₂]₃[M(CN)₆]₂ precipitates in thesolid states, and <3> Preparation of CdSe nano-particles to prevent from emitting HCNgas by keeping basic condition without bad ions at early steps. After checking orderstreatment procedures and chemical reactions for model systems, we have tested andtreated actual waste solutions containing cyanide and Cu²⁺ ions successfully. Sincepoisonous KCN solutions should be used carefully, chemistry must develop safeprocedures for dispose waste solutions of KCN treatment.