Research Article

Austin J Biotechnol Bioeng. 2014;1(2): 5.

Adsorption of Hexavalent Chromium onto Activated Carbon

Mohanty S, Bal B and Das AP*

Bioengineering Laboratory, Centre of Biotechnology, Siksha O Anusandhan University, India

*Corresponding author: Das AP, Bioengineering Laboratory, Centre of Biotechnology, Siksha O Anusandhan University, Khandagiri Square, Bhubaneswar, India.

Received: July 18, 2014; Accepted: August 11, 2014; Published: August 12, 2014

Abstract

Background: Hexavalent chromium is a well established carcinogenic and mutagenic contaminant, frequently cause to come into the surroundings through various related study of origins and development of human activities. Among a variety of approaches, adsorption of toxicant hexavalent chromium by activated carbon is measured to be a feasible option to remediate Cr (VI) contagion, from ground and water beds, effusing from mopes of chromite quarry and mine waste.

Methods: In this present lesson, removal of Cr (VI) via adsorption on activated carbon was investigated. The studies were conducted by varying different parametric quantity such as initial pH, adsorbent dosage, contact time and temperature. Experimental studies found that under optimized condition, the activated carbon is able to remove 99% of Cr (VI) with initial concentration of 10 mg/L in 6 hr, at pH- 6 and temperature-30°C.

Results: The result suggests that the rate of adsorption is highly influenced by the process parameters. The percentage of adsorption increases with increase in adsorbent dose (1.5 gm). In the initial stages the rate of Cr (VI) adsorption was high, then gradually decreases and remained constant. At pH 6 effectiveness of adsorption of activated carbon was found to be highest. With increase in temperature the adsorption increased i.e. at 30°C almost 95% Cr (VI) was adsorbed. The optimal parameter for chromium uptake was dependent on chromium concentration, absorbent dose-1.5 gm, pH -6, temperature-30°C, contact time-6 hr. The maximum efficiencies of chromium removal were found 99% with all above optimized parameters using activated carbon.

Conclusion: The current investigation reports the removal of Cr (VI) from an aquatic system through adsorption on to activated carbon equipped from coconut shells with a maximum removal efficiency of 99% within 6 hours. Thus activated carbon prepared from coconut shell can perform as a noble adsorbent for the adsorption of chromium from industrial effluents.

Keywords: Adsorption; Activated carbon; Hexavalent chromium; Bioremediation

Introduction

Hexavalent chromium is highly toxic for the environment ensuing from haphazard mining, industrial effluents, tanning wastes and steel alloys etc [1]. Although chromium (Cr) is measured as a necessary nutrient but it is one of the toxic pollutants in chromite mines and several industries which has become a major area of concern. The centralized maximum concentration level (MCL) for Chromium water consumption is 100 ug/L and the National Institute for Occupational Health and Safety (NIOSH) urge of an coverage border for Cr (VI) of 1 ug/m3 and an overexposure frontier for Cr (0), Cr (II) and Cr (III) of 500 ug/m3 for a 10 hr workday, 40 hr week. From all anthropogenetic origin approximately 35% of Cr is released as hexavalent chromium Cr (VI) into the environment [2]. The greatest anthropogenic sources emissions are chromite mining, Cr plating, chemical industrialized of Cr and cooling system by evaporation [3]. Chromium have an existence in numerous oxidation states ranging from Cr (-II) to Cr (VI) [4].

The major leading oxidation states of chromium are Cr (VI) and Cr (III) which are obtained from the environment. Cr (VI) is extremely portable and has a capability of being dissolved quickly whereas Cr (III) is comparatively inert, chemically steadier and less bio-available due to its insignificant porosity to bio-membranes [5]. Cr (VI) causes genetic mutations and cancer in the level brings out ecological and wellness harm because of its elevated hypertoxicity [6], mutagenicity [7] and carcinogenicity [8]. Presently waste matter is treated with chemical removal, ferrous sulfate, followed by precipitation with alkaline or ion exchange removal; nevertheless, the process of adsorption is mostly based on precipitation and supplemented treatment to remediate those effluents is to be sorted. The quest for alternative novel and modern skill has close attention of awareness on bioremediation of toxic heavy elements. Detoxification mechanism used by the engineers' could be an alternative unconventional method for the removal of Cr (VI) pollution [9]. Chromium is essential to human activity: a dose of 0.1-0.3 ppm per day is necessary for usual growth which generally comes through different foods accessories & fruit drinks. Cr (III) plays a crucial responsibility in animal and plant metabolic activity, whereas hexavalent chromium is straightly toxic to animals, humans and plants. Thus management of the heavy metal to remediate the waste material before emitting into the surroundings becomes inevitable.

Contamination and elevated concentration of hexavalent chromium effluence has contributed a major health hazard affecting more than 2 lakh mine workers and population residing in the Sukinda chromite mine of Odisha, India. Several studies suggest all forms of Cr (VI) are regarded as carcinogenic to workers however the most significant routes of professional exposure to contaminant are breathing and dermal contact [10-12]. Different methods have been suggested for the removals of metal contaminant such as bioremediation, solvent extraction, electrolysis, reverse osmosis, ion exchange adsorption & electrochemical precipitation [13,9]. Adsorption is the good and promising method & a possible unconventional way for the removal of the effluent among all those techniques. Different types of absorbents for the removal pollutant have been reported earlier by means of adsorbents like granular activated carbon, activated shedge, soya cake, husk of rice based activated carbon and fly ash, etc [14]. In the present study, the adsorption capacity of Cr (VI) onto activated carbon was studied. The effect of adsorbent dose, contact time, temperature, pH, and concentration of adsorbate on percentage of adsorption has also been investigated. The overall schematic presentation of the Cr (VI) adsorption process is explained in (Figure 1).