Determinación del contenido de zinc en residuos producidos durante el proceso de galvanizado por inmersión

In the hot galvanizing process, remnants are produced that must be removed to avoid a poor quality in the coating of the product. During the hot dip galvanizing process, by-products are obtained both in the tubs and in galvanizing pails, which can be reused. The objective of this study was to recover Zinc from the by- products generated during the hot dip galvanizing process. The study was carried out by characterizing the chemical composition, density, and quantity of the by-products generated during the galvanizing process, which were recovered: Zinc, dross, droplet, and Zinc fines. The monthly average of the by- products generated for one year was 6,900 kg of dross, 5,800 kg of drop and 5,300 kg of zinc fines. 6500 kg of recovered Zinc were obtained. 43% Zinc was recovered. The results were favorable to be able to carry out the recovery of the mineral. It is concluded that it is necessary to work on the recovery of Zinc, since there will be economic savings, and it will also collaborate with the care of the environment by preventing Zinc residues from going to wastewater.

Zinc stearate from galvanizing waste materials and its use as thermal stabilizer in PVC industries

Galvanizing industries of Bangladesh produce profuse amount of environmentally hazardous solid waste materials like zinc dross which contains significant amount of valuable zinc and harmful heavy lead. Zinc was extracted as zinc chloride (ZnCl2) from zinc dross. Zinc stearate (ZnSt2) samples were prepared by precipitation method from stearic acid, sodium hydroxide and ZnCl2 by varying the amount of the reagents and product yield found within the range 96.06-99.18%. Characteristic peaks of ZnSt2 were investigated by Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimeter (DSC) onset curve assigned accurate melting point within the range 122.84-124.03°C. Surface morphology of ZnSt2 was observed by Scanning Electron Microscope (SEM) and products had semi-crystalline structure. Thermal stability of ZnSt2 was evaluated by Thermo-gravimetric Analyzer (TGA) that complied with literature. A combination of ZnSt2 and Calcium stearate (CaSt2) at 1:1 ratio was used as thermal stabilizer in the powder commercial grade PVC resin and performed better thermal stability. The dehydrochlorination temperature of PVC with mixed stearates was 344.67±1.04°C for 10% (w/w) loading whereas for PVC, PVC with 10% (w/w) ZnSt2 and PVC with 10% (w/w) CaSt2, it was 269.83±1.04°C, 317.33±1.26°C and 323.33±2.08°C respectively.Bangladesh J. Sci. Ind. Res. 51(4), 261-270, 2016