Performance Assessment of natural adsorbent using Barberry Root in the removal of Chromium from aqueous environment (Case study: Groundwater resource of Birjand)

The potential sources of Cr (VI) are various effluents from metallurgy, electroplating, leather tanning, textile dyeing, paint, ink, and aluminum manufacturing industries. These industrial effluents can contain Cr (VI), in the concentration range of 10 to 100 mg/L (Nakano et al 2000), which is much higher than the standard limit; 0.5 mg/L in industrial wastewater (EPA). In aqueous systems, chromium usually exists in both trivalent [Cr (III)] and Cr (VI) forms. Although Cr (III) is considered an essential trace element, Cr (VI) is toxic, carcinogenic, mutagenic and teratogenic (Wittbrodt & Palmer 1995). Therefore, the removal of Cr (VI) from industrial wastewater is of particular concern. Advances in water and wastewater treatment technology need spur for the development of technologies that may be more effective and less costly. Nowadays, the contamination of water by toxic heavy metals through the discharge of industrial wastewater is a worldwide environmental problem that this pollution can also have a source of groundwater with the geological formation. There are various methods for removing heavy metals including chemical precipitation, membrane filtration, ion exchange, liquid extraction or electro-dialysis (Park 2007). However, these methods are not widely used due to their high cost and low feasibility for small-scale industries (Elangovan 2008). The widespread industrial use of low cost adsorbents for wastewater treatment is strongly recommended at present, due to their local availability, technical feasibility, engineering applicability and cost effectiveness (Girgis 2002; Serrano 2004). Most agriculture wastes or by products are considered to be low value products. As an alternative, a variety of inexpensive biomasses have been studied for their ability to remove Cr (VI) from aqueous solutions. Among these low cost adsorbents are microorganisms, seaweed, clay minerals, agricultural wastes, industrial wastes and various other low-cost materials (Bailay et al 1999; Dokken et al 1999; Park et al 2001; Selvi et al 2001; Rao et al 2002; Babel & Kurniawan 2003; Lakatos et al 2003; Yu et al 2003; Kobya 2004; Bishnoi et al 2004; Gupta & Ali 2004; Chun et al 2004; Grag et al 2004; Sheng et al 2004; Kobya et al 2005; Khezami & Capart 2005; Prasenjit & Sumathi, 2005; Sen et al 2005; Khosravi et al 2005 ; Verma et al 2006; Potgieter et al 2006; Wang & Qin 2006; Zulkali et al 2006; Yasemin et al 2007; Sciban et al 2007; Gerente et al 2007; Igwe et al 2007; Cetin et al 2007; Benhima et al 2008; Rocha et al 2009; Jaman et al 2009; Miralles et al 2010; Boudrahem et al 2011; Anwar et al 2010; Revathi et al 2012 ; Bai et al 2011; Ramalingam et al 2012). The dynamics is an essential aspect of the adsorption process especially for practical applications. Therefore, the present investigation has been undertaken for studying the dynamic behavior of adsorption through batch experiments performed under different conditions of contact time, pH, adsorbent, initial concentration, particle size and temperature. A well-fitted kinetic equation was used to evaluate the suitable operational conditions for the removal process, and a Langmuir-type isotherm was modeled using kinetic data and experimental results.
Matherials & Preparation of the soluble metal The stock solutions of Cr (VI) (1000 mg/l) were prepared by dissolving K2Cr2O7 (analytical reagent grade) in distilled water. The desired Cr (VI) concentrations were prepared from the stock solution by making fresh dilutions for each sorption experiment. The initial pH of the solution was adjusted by using a solution of HNO3 or NaOH.
Preparation of adsorbent:Barberry roots were collected from South Khorasan, Birjand areas and soaked in distilled water for 24 hr before putting in an oven at 70°C for 24 hours. Barberry roots using Mill Were powdered. Powders were sieved through a 100 mesh and were stored in a container away from moisture.
Batch adsorption experiments: Adsorption experiments were carried out in batch mode. In order to investigate the nature of Cr (VI), initially the effect of pH on percentage removal was carried out and then further experiments on the effect of contact time, adsorption weight, initial concentration and temperature were conducted by using optimized pH. Only one parameter was changed at a time while others were maintained constant. In the first set of experiment, percentage adsorption was studied at various pH of (1.5–9) at constant adsorbent weight of 0.1 g/100 ml, initial Cr (VI) of 50 ppm and the predetermined time (10min) in a rotary shaker at a speed of 200rpm using series of 100 mL Erlenmeyer flasks. Next second set of experiments were conducted with various contact time, initial Cr (VI) concentration (50ppm) at constant adsorbent weight (0.1 g/100 ml) and at optimized pH 1.5. In the third set of experiment adsorption weight was varied (0.05–1 g/100 ml) while other parameters such as initial Cr (VI) concentration (50 mg/l), optimum time (90min) and optimum solution pH kept constant. In the fourth set of experiment Cr (VI) concentration was varied (25–200 ppm) and in the last set of experiment, temperature was varied at six different temperatures viz., 22, 25, 35, 40, 45 and 50°C in a thermostat attached with a shaker. The constancy of the temperature was maintained with an accuracy of ± 0.5 ºC.22-50), and other optimum parameters kept constant. After completion of every set of experiments the supernatant was separated by filtration using Whatman filter paper and only 10ml of each sample was stored for residual chromium analysis. The pH of each solution was adjusted using required quantity of HNO3 or NaOH before mixing the adsorbent. Three replicates per sample were done and the average results are taken for calculation. The filtrate was analyzed using Atomic Absorption Spectrophotometry (AAS) (Shimadzu AA-6300; 228.63 nm). All the experiments were performed in.