engleski

Characterization and environmental impact assessment of jarosite process tailing waste

Jarosite waste, originating from zinc extraction industry, is considered hazardous due to the presence and the mobility of toxic metals that it contains. Its worldwide disposal in many tailing damps has become a major environmental concern. The current thesis considers the jarosite process tailing waste in Mitrovica Industrial Park, Kosovo in order to evaluate the characteristics of jarosite waste, identify the potential environmental impacts and understand its potential for recycling or utilization as a challenge for development of positive “green” image environmental protection and sustainable hazard waste management in future. The thesis presents: 1) detail characterization and evaluation of environmental risk of jarosite process tailing waste ; 2) examines the metal bioavailability and metal fractioning in jarosite waste ; 3) estimates the amount of potential toxic elements and ecological risk index and 4) presents the most promising options for recycling and utilization of jarosite waste. In particular, the thesis intends, in one hand to solve the problem of environmental pollution by transferring the negative features of jarosite waste into the positive contribution through neutralizing the harmful characteristics and on the other hand, the work performed to contribute obtaining valuable materials from jarosite waste with an economic benefit. From this point of view, three jarosite samples of jarosite waste collected on three different depths (0.20 m, 1 m and 2 m) were characterised using X- ray powder diffraction (XRD) analysis, scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS) analysis, thermo gravimetric analysis (TG) / differential thermal analysis (DTA) as well as Raman and Fourier transform infrared (FTIR) spectroscopy analysis. The results obtained confirmed the presence of ammonium jarosite in the jarosite tailing waste in Mitrovica indus-trial Park. The presence of gypsum, franklinite, quartz, and barite was observed as well. It was indicated that the ammonium jarosite persists at 300 °C, along this line it show signs of de-composition at 400 °C and it is fully decomposed at 500 °C. The decomposition of ammonium jarosite occurred in four consecutive stages. A jarosite waste treated at different range of temperatures from 200 °C to 1000 °C produced soluble iron sulphate and insoluble residue from which hematite, magnetite and franklinite could be magnetically separated. The remaining non-magnetic residue contains large quantities of sparingly soluble PbSO4, BaSO4, CaSO4 and quartz that could be used and obtain valuable raw materials.To assess the metal bioavailability and metal fractioning in the jarosite waste, the modified BCR sequential extraction and two leaching experiments up to 21 days duration were performed. The tests evaluated the mobility of major and minor elements under the deionized water and acid rain conditions. The Zn, Cd, Co, Cu, Pb and As were the mostly released elements and the metal release risk for these elements is still very high due to low pH and acid rain.The applied modified BCR sequential extraction method and potential ecological risk index method confirmed that the mobility of Cd has major environmental impact. The order of potential ecological risk is Cd > Zn > Cu > Ni for all samples of three different depths. The study samples showed interesting features based on the results obtained for the metal partitioning present in jarosite waste. The significant long- term beneficial effects to the jarosite waste stabilization are suggested together with best practice examples on the waste utilization in the building materials such as bricks, blocks, cement, tiles and composites and metal recovery.

characterization ; jarosite waste ; thermal decomposition ; leaching test ; sequential extraction ; environmental potential risk index ; utilization.

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