Removal of Arsenic from Aqueous Solutions Using Welding Iron Waste

Original Article Removal of Arsenic from Aqueous Solutions Using Welding Iron Waste Abooalfazl Azhdarpoor1, Roya Nikmanesh2, Mohammad Reza Samaei1 Department of Environmental Health, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran; 2 Department of Environmental Health Engineering, Shiraz University of Medical Sciences, Shiraz, Iran 1 Correspondence: Abooalfazl Azhdarpoor, Department of Environmental Health, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran Tel: +98 71 37251001 Fax: +98 71 37260225 Email: Received: 2 November 2014 Revised: 10 December 2014 Accepted: 18 January 2015 Abstract Background: Contamination of water with arsenic has attracted the researchers’ attention as a global problem in recent years and has been observed in some parts of Iran. The purpose of this study is to assess the efficiency of welding iron waste in removing arsenic from aqueous solutions. Methods: In this study, the effects of different parameters, such as pH (3-9), initial concentration of arsenic (100-3000 µg/l), contact time (5-90min) and adsorbent dose (2.5-20 g/l), were studied. The final concentrations of arsenic were analyzed by atomic absorption. Results: The results indicated that at pH=3 and fixed dose of 1 g, arsenic removal efficiency of iron waste was 89.73%. By increasing the pH to 7, the removal efficiency increased to 96.44%. Also, an increase in the amount of iron waste from 2.5 to 10g/l, the removal rate increased from about 42.37% to 96.70%. For contact times of 5 and 30 minutes, the removal rate was 9% and 96.62%, respectively. Then, with increasing the contact time to 90 minutes, the removal rate increased to 99.24%. Correlation coefficient of Freundlich and Langmuir isotherms for As(III) was 0.7593 and 0.9979, respectively . Conclusion: The results of the study showed that welding iron waste has a high potential as an effective, fast and cheap method for removal of arsenate and arsenite from aqueous solutions. Please cite this article as: Azhdarpoor A, Nikmanesh R, Samaei MR. Removal of Arsenic from Aqueous Solutions Using Welding Iron Waste. J Health Sci Surveillance Sys. 2015;3(2):56-63. Keywords: Iron waste, Arsenite, Aqueous solutions, Arsenic removal Introduction One of the most common pollutants and toxic agents for groundwater is arsenic. In many countries, especially developing ones, arsenic concentrations in the drinking water has exceeded the standards and has received attention as a big problem.1,2 Arsenic is a toxic element in drinking water that enters the human body and has harmful health effects. Arsenic enters water supplies from natural and synthetic processes,3 including natural processes, such as earth erosion, drainage water from soil washing and weathering, industrial activities for mining, and smelting of metals from ores, combustion of fossil fuels, application of arsenic-bearing pesticides and plants’ wastewater which pollutes the air, soil and water with arsenic.4 Arsenic in groundwater is mainly found in the form of arsenate(HAsO32-, H2AsO3-, H3ASO3 56 and arsenite (HAsO42-, H2AsO4-, H3AsO4).5,6 Arsenic is a toxic cumulative substance, and is an inhibitor of SH group enzymes. The trivalent arsenic (arsenate) is usually more toxic than the pentavalent form (arsenate).7 Due to the presence of arsenic in drinking water sources, serious health problems have arisen in several countries, including Argentina, Bangladesh, Chile, China, India, Italy, Japan, Mexico, Malaysia, Nepal, Poland, Taiwan, Vietnam, and Iran. Due to the importance of the issue, the US Environmental Protection Agency reduced its MCL standard for arsenic from 50 to 10 ppb in January 2001.3,8 The World Health Organization has adopted MCL for arsenic of 10 micrograms per liter.6,7,9 Thus, given the enormous risks of arsenic in water supplies, removing it from water sources is very important. In recent years, various treatment methods have been proposed and used to remove arsenic from J Health Sci Surveillance Sys April 2015; Vol 3; No 2 Arsenic removal using iron waste water plants, such as chemical oxidation, dissolved air flotation, surface adsorption, ion exchange, membrane processes, electrical coagulation, chemical coagulation, and biological processes. According to their particular circumstances, water treatment systems may choose one of these methods with regard to their economic and management considerations.10,11 While these methods are widely used, they are faced with such problems as the high costs of operation, waste treatment, consumption of large amounts of materials and production of high volumes of sludge.12,13 Therefore the use of zero-valent metals (such as Fe0( has been studied as an effective method for reducing water contamination in recent years. The use of Fe0 has received more attention in this regard because of its frequency, cost-effectiveness, non-toxic nature, quick reaction, and high efficiency and ability to break down contaminants.6,7,9,10 The mechanism of removing contaminants by Fe0 includes reduction or absorption processes.11 In aerobic conditions, both reduction and absorption processes are involved in arsenic removal; however, due to the greater speed and efficiency of the absorption process, it is introduced as the main factor.14 Therefore, given the benefits mentioned for using Fe0, the main objective of this study is to evaluate the direct use of welding iron waste for removal of arsenic from aqueous solution and the effect of various parameters on the process. for testing was obtained via diluting the stock solution. Materials and Methods The Effect of Initial pH on the Arsenite Removal Efficiency This is fundamentally a laboratory scale study. The purpose of this study was to assess the efficiency of welding iron waste in removing arsenic from aqueous solutions. The effects of operating parameters, such as pH,3-9 initial of arsenic concentration (100-3000 µg/l), contact time (5-90 min), and adsorbent dose (2.5-20 g/L) were studied. This study was carried out at the main laboratory of environmental sciences at Shiraz University of Medical Sciences in 2014. In this study, as seen in Figure 1, the effect of pH on arsenate removal by welding iron waste in the range of 3-9 with initial arsenite concentration of 500 µg /l and reaction time of 30 minutes was examined. Based on the results presented in this Figure, with an increase in pH, the removal efficiency increased. The results also indicated that at pH=3, the removal efficiency was 89.73%. By increasing the pH to 7, the removal efficiency increased to 96.44%. After that, increasing the pH to 9 did not reveal a significant effect on arsenate removal efficiency which gets close to an almost constant removal efficiency rate. Thus, these results show that the initial pH of the solution is important in achieving maximum removal efficiency. In this study, though the removal efficiency was more than 89% for all the studied pH, the hi (...truncated)