مقاله انگلیسی رایگان در مورد حذف فلزات سنگین توسط نانوسیم های اکسید قلع – اسپرینگر 2018

In the present research, the removal of lead(II) and copper(II) from aqueous solutions is studied, using SnO2 nanowires as new adsorbent on solid-phase extraction disk and compared with pine core and buttonwood as biosorbents. Batch adsorption experiments were performed as a function of pH, adsorption time, solute concentration and adsorbent dose for biosorbents. Also, the pH, transfer rate of solution and metal concentration were selected as experimental parameters for the removal of heavy metals by SnO2 nanowires. All of the parameters were optimized by experimental design method for sorbents. The experimental equilibrium adsorption data are tested for the Langmuir and Freundlich equations. Results indicate the following order to fit the isotherms: Langmuir[Freundlich, in case of lead and copper ions. The removal of Cu(II) and Pb(II) was performed by selected sorbents in the presence of interferences ions. This led to no remarkable decrease in the removal efficiency of SnO2 nanowires. Using the SnO2 nanowires in the wastewater treatment indicated 96.8 and 85.28% removal efficiency in only 7 min for Pb(II) and Cu(II), respectively. SnO2 nanowires were found as reusable sorbent. Therefore, SnO2 nanowires have a good potential for application in environmental protection.

Introduction

Heavy metal pollution has become one of the major threats to the environment due to their toxicities, nonbiodegradability, bioaccumulation in human body and food chain and most likely carcinogenicities to human (Stafiej and Pyrzynska 2007). Accumulation of heavy metals in the environment causes heavy metal poisoning even when they are present in low concentrations (Hsieh and Horng 2007). The major source for heavy metal contamination of aquatic environments is industrial activities such as refining, painting, metal plating and cleaning, battery and car radiator manufacturing, textile and leather tannins (Rao et al. 2007; Shahidi et al. 2016; Simonovic et al. 2007; Toprak and Girgin 2000). Lead, copper, mercury, chromium, arsenic, cadmium, zinc and nickel are the most common contaminants found in environmental water samples (Rao et al. 2007). Pb(II) and Cu(II) are the metal ions that are used most widely in industry. In the recent years, it is of vital importance to determine and identify lead and copper ions because of high toxicity. They can cause a variety of negative effects on human health, for example, neurotoxicity, jaundice, liver toxicity, anemia, encephalopathy, hepatitis and nephritic syndrome (Singha and Das 2012). The permissible limit of lead and copper was notified by World Health Organization as 10 lg l-1 and 1.5 mg l-1 , respectively (Goel et al. 2005). A wide variety of techniques were applied for the elimination of metal pollutants from aqueous solutions including ion exchange, reverse osmosis, membrane filtration, evaporation, solvent extraction and adsorption (Fu and Wang 2011; Kumar et al. 2017; Kamal et al. 2017). Among these existing techniques, adsorption was developed due to high yield, easy operation and the variety of adsorbents. However, in recent years due to the application of various biomaterials for the sorption purpose, the term adsorption has become more popular as biosorption. A number of biomaterials were widely employed for metal ion removal from aqueous solutions including agricultural wastes, biopolymers and plant wastes (Pan et al. 2009; Mishra et al. 1996). Phytoremediation has emerged as an environment-friendly technology that employs plants for the uptake of heavy metals (Boonyapookana et al. 2005). This technology involves growing plants on appropriate sites and application of dried powder of root, leaves or skin of plants in water (Weerasinghe et al. 2008; Lasat 2002). Development of nanotechnology introduced a new insight into sorbent for extraction of compounds or removal of pollutants (Alizadeh and Najafi 2013; Alizadeh et al. 2016; Alizadeh 2016). In recent years, the development of nanotechnology in preparation of sorbents has enhanced the efficiency of heavy metal removing.