Materiais reciclados de baterias exauridas de Zn-MnO2 e de rejeitos da indústria de mineração de ferro: síntese, caracterização e aplicações

Abstract

In this study residual materials were employed from spent alkaline batteries and iron mining tailings for direct use or as starting materials in dry and wet syntheses and applications in electroanalytical and heterogeneous photocatalysis. The materials used in the applications were the REJ and MAC starting materials and the materials synthesized from these: COP_REJCMC450 (wet method: synthesis by co-precipitation), FerCer1, CER1000 and CER_CMC1000 (dry method: solid state synthesis). All starting and synthesized materials were characterized by XRD, SEM/EDX, MET, BET. The FerCer1 material was used in the development of the FerCer1/GCE non-enzymatic electrochemical sensor for ascorbic acid determination. Highlight for the development of a portable, fast and sustainable method to determine copper in alcoholic beverages, having been verified against a reference sample for cachaça. Square wave voltammetry (SWV) and screen-printed carbon electrodes modified with a thin and homogeneous film formed with the active material of the cathode (CAM) of spent Zn-MnO2 batteries and with corn starch (CAM/Starch/SPCE) were used. The SWV operational parameters for copper determination were optimized through experimental design and the optimal values obtained were: step potential (10 mV), modulation amplitude (80 mV) and frequency (4 Hz). The method used 0.1 mol L-1 H2SO4 as supporting electrolyte and presented a limit of detection of 0.024 µmol L-1 (R2 = 0.997). Recovery tests in cachaça, whiskey, vodka, gin and beer ranged from 93.3% to 108%, indicating that there is no matrix effect. The method was verified for cachaça analysis by analyzing a sample enrolled in a proficiency test program. All materials mentioned were also applied in heterogeneous photocatalysis studies in the decolorization of methylene blue dye using solar radiation, light cabin (UVA, UVC, UVA/US), presenting satisfactory results for the REJ, CER1000 and COP_REJCMC450 samples that obtained efficiencies of dye discoloration greater than 80% for experiments with solar radiation and UVA/US. The construction of an electrochemical sensor from spent Zn-MnO2 batteries and low cost materials such as starch for copper determination in alcoholic beverages, as well as application in heterogeneous photocatalysis also using iron mining tailings are sustainable strategies to minimize environmental and health problems associated with battery waste disposal and alternatives for inadequate disposal of iron mining tailings.