Articulo Medio Ambiente

Selective Removal of Heavy Metals

Subject Area 6.1

Subject Area 6.1: Sample preparations, separation techniques and analytical methods to determine organic and inorganic compounds
Research Article

Selective Removal of Heavy Metals from Metal-Bearing Wastewater in a Cascade Line Reactor*
Jelena Pavloviƒ1**, Sreƒko Stopiƒ2, Bernd Friedrich2 and ðeljko Kamberoviƒ1
1 University

ofBelgrade, Faculty of Technology and Metallurgy, Department of Metallurgical Engineering, Karnegijeva 4, 11120 Belgrade, Serbia and Montenegro 2 RWTH Aachen, IME, Process Metallurgy and Metal Recycling, Intzestrasse 3, 52072 Aachen, Germany **Corresponding author (jpavlovic@tmf.bg.ac.yu)
DOI: http://dx.doi.org/10.1065/espr2006.09.345 Please cite this paper as: Pavloviƒ J, Stopiƒ S, Friedrich B,Kamberoviƒ Z (2007): Selective Removal of Heavy Metals from Metal-Bearing Wastewater in a Cascade Line Reactor. Env Sci Pollut Res 14 (7) 518–522 Abstract

Goal, Scope and Background. This paper is a part of the research work on 'Integrated treatment of industrial wastes towards prevention of regional water resources contamination – INTREAT' the project. It addresses the environmental pollutionproblems associated with solid and liquid waste/effluents produced by sulfide ore mining and metallurgical activities in the Copper Mining and Smelting Complex Bor (RTB-BOR), Serbia. However, since the minimum solubility for the different metals usually found in the polluted water occurs at different pH values and the hydroxide precipitates are amphoteric in nature, selective removal of mixed metalscould be achieved as the multiple stage precipitation. For this reason, acid mine water had to be treated in multiple stages in a continuous precipitation system-cascade line reactor. Materials and Methods. All experiments were performed using synthetic metal-bearing effluent with chemical a composition similar to the effluent from open pit, Copper Mining and Smelting Complex Bor (RTB-BOR). Thateffluent is characterized by low pH (1.78) due to the content of sulfuric acid and heavy metals, such as Cu, Fe, Ni, Mn, Zn with concentrations of 76.680, 26.130, 0.113, 11.490, 1.020 mg/dm3, respectively. The cascade line reactor is equipped with the following components: for feeding of effluents, for injection of the precipitation agent, for pH measurements and control, and for removal of theprocess gases. The precipitation agent was 1M NaOH. In each of the three reactors, a changing of pH and temperature was observed. In order to verify efficiency of heavy metals removal, chemical analyses of samples taken at different pH was done using AES-ICP. Results. Consumption of NaOH in reactors was 370 cm3, 40 cm3 and 80 cm3, respectively. Total time of the experiment was 4 h including feeding ofthe first reactor. The time necessary to achieve the defined pH value was 25 min for the first reactor and 13 min for both second and third reactors. Taking into account the complete process in the cascade line reactor, the difference between maximum and minimum temperature was as low as 6°C. The quantity of solid residue in reactors respectively was 0.62 g, 2.05 g and 3.91 g. In the case ofcopper, minimum achieved concentration was 0.62 mg/dm3 at pH = 10.4. At pH = 4.50 content of iron

has rapidly decreased to < 0.1 mg/dm3 and maintained constant at all higher pH values. That means that precipitation has already ended at pH=4.5 and maximum efficiency of iron removal was 99.53%. The concentration of manganese was minimum at pH value of 11.0. Minimum obtained concentration of Zn was 2.18mg/dm3 at a pH value of 11. If pH value is higher than 11, Zn can be re-dissolved. The maximum efficiency of Ni removal reached 76.30% at a pH value of 10.4. Discussion. Obtained results show that efficiency of copper, iron and manganese removal is very satisfactory (higher than 90%). The obtained efficiency of Zn and Ni removal is lower (72.30% and 76.31%, respectively). The treated effluent...