Remediation of cr (vi) from contaminated water by activated carbon entrapped in calcium alginate beads

Project Abstract

<p> Cr (VI) is a well-known highly toxic metal. This project focuses on the removal of Cr (VI) from contaminated water using activated carbon entrapped in calcium alginate beads. Activated carbon used for this work was prepared from an organic waste material called walnut shell by carbonization using phosphoric acid as an activating agent. 0.5g of activated carbon was added to 10mL of 4% sodium alginate solution.The mixture was promptly dropped into 3.5% aqueous solution of calcium chloride (CaCl2) using a pump.It was then continuously stirred until homogenous mixture was obtained.Finally the calcium alginate beads formed were hardened and rinsed. Batch experiments were carried out in the laboratory to evaluate the efficacy of activated carbon entrapped in calcium alginate beads for the removal of Cr (VI) from contaminated water. Different masses of entrapped calcium alginate beads (0.5g, 1.0g, &amp; 1.5g) were mixed with contaminated water containing Cr (VI). It was observed that when different masses of entrapped calcium alginate beads were added to the contaminated water, the concentration of Cr (VI) present in it reduced. It was concluded that activated carbon entrapped in calcium alginate beads is effective for removing Cr (VI) in contaminated water. <br></p>

Project Overview

<p> INTRODUCTION<br>1.1 BACKGROUND<br>Hexavalent chromium Cr (VI) is a potential carcinogen, teratogen, and mutagen and is on the top priority list of toxic pollutants defined by USEPA (USEPA, 1998). Contamination of water with Cr (VI) is a worldwide problem and the remediation of contaminated site has become environmental challenge.Chromium is one of the key contaminants in the wastewaters of industrial dyes and pigments, film and photography, galvanometry and electric, metal cleaning, plating and electroplating, leather and mining (Anwar et al., 1961). While hexavalent and trivalent species of chromium are prevalent in industrial waste solutions, the hexavalent form has been considered more hazardous to public health due to its mutagenic and carcinogenic properties.<br>Chromium occurs in the environment primarily in two valence states, trivalent chromium Cr (III) and hexavalent chromium Cr (VI). Exposure may occur from natural or industrial sources of chromium. Chromium (III) is much less toxic than chromium (VI). The respiratory tract is also the major target organ for chromium (III) toxicity, similar to chromium (VI). Chromium (III) is an essential element in humans. The body can detoxify some amount of Cr(VI) to Cr (III). The respiratory tract is the major target organ for chromium (VI) toxicity, for acute (short-term) and chronic (long-term) inhalation exposures. Shortness of breath, coughing, and wheezing were reported from a case of acute exposure to chromium (VI), while perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, and other respiratory effects have been noted from chronic exposure (Danielsson et al., 1982). Human studies have clearly established that inhaled chromium (VI) is a human carcinogen, resulting in<br>an increased risk of lung cancer. Animal studies have shown chromium (VI) to cause lung tumors via inhalation exposure (Danielsson et al., 1982).<br>1.2 ACUTE EFFECTS OF CHROMIUM (VI)<br>Chromium (VI) is much more toxic than chromium (III), for both acute and chronic exposures. The respiratory tract is the major target organ for chromium (VI) following inhalation exposure in humans (Bloomfield and Blum, 1928). Shortness of breath, coughing, and wheezing were reported in cases where an individual inhaled very high concentrations of chromium trioxide. Other effects noted from acute inhalation exposure to very high concentrations of chromium (VI) include gastrointestinal and neurological effects, while dermal exposure causes skin burns in humans. Ingestion of high amounts of chromium (VI) causes gastrointestinal effects in humans and animals, including abdominal pain, vomiting, and hemorrhage. Acute animal tests have shown chromium (VI) to have extreme toxicity from inhalation and oral exposure (Davies, 1978).<br>1.3 CHRONIC EFFECTS OF CHROMIUM (VI)<br>Chronic inhalation exposure to chromium (VI) in humans results in effects on the respiratory tract, with perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, asthma, and nasal itching and soreness reported (Davies, 1978). Chronic human exposure to high levels of chromium (VI) by inhalation or oral exposure may produce effects on the liver, kidney, gastrointestinal and immune systems, and possibly the blood (Frentzel-Beyme,<br>1983). Rat studies have shown that, following inhalation exposure, the lung and kidney have the highest tissue levels of chromium. Dermal exposure to chromium (VI) may cause contact dermatitis, sensitivity, and ulceration of the skin.<br>1.4 STATEMENT OF PROBLEM<br>The presence of hexavalent chromium in water resulting from rapid industrialization and high anthropogenic activities has posted treat to man. It is therefore essential to find a cheaper way of removing Cr (VI) from waste water.<br>1.5 AIM AND OBJECTIVES OF THE PROJECT WORK<br>1) To prepare activated carbon from walnut shell by carbonization using phosphoric acid as an activating agent.<br>2)To entrap activated carbon into calcium alginate beads.<br>3) To remove Cr (VI) from contaminated water using activated carbon entrapped in calcium alginate beads. <br></p>