COMBUSTION OF CONTAMINATED SORGHUM SPP. FOR ZN EXTRACTION

Due to its properties, forage sorghum can grow under unfavorable soil conditions and in places with very harsh climatic conditions. Also, it is very tolerant of habitats that are contaminated with metals. Certain varieties of sorghum are capable of absorbing Zn from polluted soil. In this study, the optimal burning time and temperature of Sorghum spp. with the aim of obtaining ash with the highest possible concentration of Zn. Applying the chemical analysis of the homogenized initial sample of sorghum, it was established that 1 kg of sorghum contains 55.61 mg of Zn. Combustion experiments were performed at temperatures of 400, 450, 500 and 600 oC for 120, 240 and 360 minutes. In all experiments, the mass loss was approximately 90%. It was observed that the highest content of Zn has the ash that was formed after burning for 6 hours at a temperature of 500 oC. Differential thermogravimetric analysis showed that the greatest mass loss of the sample (ash) was recorded at a temperature between 150 and 400 oC. In order for the valorization of zinc from the ash to be possible, it is necessary that the ash and leachate (after washing the ash) do not contain any substance that would prevent the precipitation of zinc salts.