removal of arsenic from borous water by processed ...

15th International Mineral Processing Symposium, Istanbul-Turkey, October 19-21, 2016

REMOVAL OF ARSENIC FROM BOROUS WATER BY PROCESSED PYRITE ASH T. Türk, İ. Alp and T. Boyraz Karadeniz Technical University, Dept. of Mining Engineering, 61080, Trabzon, Turkey

Abstract: This study reports the potential use of processed pyrite ash (PPA) as adsorbent in the removal of arsenic from borated water. The samples of pyrite ash wastes used in this study were taken from Bandırma Borax and Boric Acid Establishment, Turkey. PPA was characterized by X-ray diffractometry (XRD) and Inductively Coupled Plasma Emission Spectrometry (ICP-ES) spectrophotometer. The after leaching pyrite ash appears a suitable raw material as adsorption materials containing of magnetite (Fe3O4) and hematite (Fe2O3). Boron mineralization in Emet-Hisarcık region is one of the world's largest reserves of boron. The groundwater in the region has also significant levels of boron as dissolved oxyanion. The groundwater associated with arsenical boron deposits was reported to contain up to 600 µg/L As and 1500 mg/L B. Remediation of arsenic and boron pollution in this water is therefore required. In this study, the removal of arsenic from borated waters by processed pyrite ash (PPA) was investigated. It was found that PPA could remove 99% of arsenic from ground water containing high level of boron with its ability to reduce As levels below the limit (10 µg/L As) set for potable water by World Health Organization (WHO). The results of this study showed that PPA can be used as a potent adsorbent for the removal of arsenic from the borated waters.

Key Words: Adsorption, Arsenic Removal, Borated Water, processed pyrite ash (PPA).

INTRODUCTION

Arsenic is a natural component of the earth’s crust and is a carcinogenic material. It is highly toxic, particularly in its inorganic form (WHO, 2011). The sources of arsenic involve natural 304


and anthropogenic occurrences. Anthropogenic occurrences are coal combustion, mining, industrial process, smelting, insecticides, pesticides etc (Singh et al., 2015). Arsenic exposure leads to serious health problems such as skin lesions, cancer, lung disease and diabetes (Carlin et al., 2015). Maximum admissible arsenic concentration in the drinking water is 0.01 mg/L (WHO, 2011). Various techniques have been developed to remediation of arsenic contamination. These include oxidation techniques, phytoremediation, coagulation and flocculation, electro coagulation (EC), electro-chemical arsenic remediation (ECAR), ion exchange, electro kinetics, membrane technology, reverse osmosis and adsorption (Singh et al., 2015). The adsorption technique has advantages in comparison with other techniques due to its recycling, low cost, easiness (Glocheux et al., 2013). In Turkey Bandırma Eti Mine Works, Pyrite ashes are obtained as wastes during the roasting of pyrite ores in sulfuric acid production (Türk, 2016). Pyrite ash wastes are used in a variety of fields in order to prevent pollution and recycle waste products (Alp et al., 2009). Boron is prevalent element in soil, rocks and water. It is found naturally and anthropogenically. According to research, if boron concentrations are high levels, boron can be hazardous to people, animals and plants (Wolska et al., 2013). World Health Organization (WHO) allow maximum 0.3 mg/L boron contain in drinking and non-drinking waters (Çöl and Çöl, 2003). Most popular boron minerals are borax, tincal, colemanite, ulexite and kernite. Boron mineralization in Emet-Hisarcık region is one of the world's largest reserves of boron. Unlike the other boron mineralization, it also contains arsenic minerals (orpiment and realgar), which cause arsenic pollution in the surface and ground waters within the surrounding area (Aydın et al., 2003). According to the research, arsenic concentration in ground water is very high (0.474-7.754 mg/L) and exceeds the WHO limits (Çolak et al., 2003). The objective of this study is to develop a new type of waste adsorbent that can be effective for the removal of arsenic from Borated Water. Pyrite ash was used as the adsorbent in the water treatment process.

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MATERIALS AND METHODS Processed pyrite ash wastes The samples of pyrite ash wastes used in this study were taken from Bandırma Borax and Boric Acid Establishment, Balıkesir, Turkey. In this study was used samples of processed pyrite ash wastes. The crystalline phase composition of the material was investigated for semi-quantitative X-ray diffraction analysis. A portion of each powder sample was loaded into a standard holder. The X-ray diffraction analysis was performed on a Panalytical X’Pert Pro diffractometer, equipped with Cu X-ray source and an X’Celerator detector, operating at the following conditions: 40 kV and 40 mA; range 5 - 70 deg 2θ; step size 0.017 deg 2θ; time per step 50.165 sec; fixed divergence slit, angle 0.5 0; sample rotation 1 rev/sec. The X’Pert HighScore plus software along with the PDF4/Minerals ICDD database were used for mineral identification. The quantities of the crystalline mineral phases were determined using Rietveld method. The Rietveld method is based on the calculation of the full diffraction pattern from crystal structure information. The XRD pattern shows presence of mainly hematite (Fe2O3) and magnetite (Fe3O4) and traces of quartz (SiO2) (Fig. 1). The Brunauer– Emmett–Teller (BET) method was used to determine the surface area of the PA sample and specific surface areas were 2.31 m2/g.

Fig. 1. Results of X-ray diffractogram of processed pyrite ash wastes 306


Adsorption experiments All adsorption experiments were done in a temperature controlled bath shaker (Wiggen Hauser SI-100T) for a predetermined contact time, at 200 rpm and at room temperature (25°C). Water samples taken from different parts of Emet-Hisarcik (Turkey) are stored in plastic containers. Characterization of natural water samples were analyzed by inductively coupled plasma optical emission spectrometry system Hydride (HG-ICP-OES). The tests of As(V) adsorption from natural solution with PPA were performed under initial As(V) concentrations 600 µg/L, initial pH 9, PA dosages (70, 50, 20, 10 and 5 g/L) and contact time (5 hour). At the end of the contact period, the mixture was then centrifuged for 10 min. at 4000 rpm and the final pH of the supernatants was measured and the supernatants are analyzed for arsenate using a continuous hydride generation unit on a Inductively Coupled Plasma Optical Emission (HG-ICP-OES) spectrophotometer.

RESULTS AND DISCUSSION

Adsorption of As(V) by PPA pH was kept constant at pH 9 in the adsorption tests due to the alkaline nature of the natural solutions used in this study. Fig. 2 shows the effect of PPA dosage on the removal of As(V). The arsenate removal efficiency increased with increasing the amount of PPA added in the range of 5-70 g/L. An adsorbent dosage of 5 g/L was required to reduce As concentration down to the desired levels of