مطالعه ترمودینامیکی و جذب سطحی آرسنیک (V) از محلول آبی
Abstract
Introduction
Materials and methods
Results and discussion
Conclusion
References
Abstract
Recently, arsenic-contaminated water has become a big concern. Therefore, the present study aimed to absorb arsenic from the aqueous solution using modifed saxaul tree ash. Arsenic adsorption process was performed in vitro by investigating the efect of various parameters such as pH, contact time, arsenic concentrations, temperature and adsorbent dosage on the adsorption efciency. Isotherms, kinetics and thermodynamic studies were also conducted to better understand the process of adsorption. Maximum level of arsenic adsorption was obtained at a pH of 7, adsorbent dosage of 1.5 g/L, contact time of 60 min, initial arsenic concentration of 250 µg/l and temperature of 323 K. The amount of adsorbed arsenic was increased with increasing initial concentration of arsenic and temperature. Freundlich adsorption isotherm clearly described the arsenic adsorption by modifed saxaul ash. Based on the results obtained, it could be concluded that the modifed saxaul ash can efciently remove arsenic from its aqueous solutions.
Introduction
Contamination of underground water caused by heavy metals is one of the most important hazards to water resources (Asgari et al. 2008). Arsenic is the third element of group V of the periodic table with atomic number of 32 and relative atomic mass of 74.92 (Golami et al. 2009). Arsenic concentrations are in the range of 2–5 ppm (Uddin et al. 2006). Arsenic contaminates the surface and underground water resources within the natural processes such as dissolving minerals, chemical decomposition and corruption, and human activities like animal husbandry, medicine, industry, electronics and metallurgy (Golami et al. 2009; Uddin et al. 2006; Zaw and Emett 2002). Human activities are the main cause of arsenic contamination of surface water and groundwater (Jafari-Mansoorian et al. 2016). Arsenic compounds based on the origin of production are mobile in the environment and could get into the food chain and hydrological cycle by rainfall (Babaakbry Sari et al. 2014). Arsenic is a toxic and accumulative substance and can inhibit SH-group enzymes. Trivalent arsenic (arsenite) is more toxic than arsenic (V) (arsenate) due to its high portability (Tyrovola et al. 2006; Triszcz et al. 2009). Arsenic may cause dysfunction in digestive system, shock leading to death, pulmonary and respiratory failures (Golami et al. 2009; Zaw and Emett 2002; Triszcz et al. 2009). It is also known as a carcinogenic substance and causes testicular, bladder, lung and liver cancers (Golami et al. 2009; Smedley and Kinniburgh. 2002). The resulting complications depend on factors such as duration of exposure, way of entering to body, type and sources of arsenic (Smith et al. 2000).