As (V) removal from aqueous solutions with magnetic activated carbon prepared from almond shell, apricot and peach stones mixture

Arsenic pollution, which has serious carcinogenic and toxic effects even at very low concentrations, has been a serious problem for public health for a long time. Arsenic pollution in drinking water and water resources in many countries around the world continues to threat human health. Arsenic contamination is caused by natural processes such as mineral weathering and dissolution resulting from a change in the geo-chemical environment to a reductive condition and by human activities such as mining wastes, petroleum refining, sewage sludge, agricultural chemicals, ceramic manufacturing industries and coal fly ash. It occurs in the forms of organic (usually occurs less than 1 μg/L in natural conditions) and inorganic in waters. Arsenate (As(V)) is the predominant and stable inorganic arsenic form in the oxygen-rich aerobic environments, while arsenite (As(III)) occurs (above pH 9.3) in reducing anaerobic environments. Owing to epidemiological evidence linking arsenic and cancer, maximum concentration level in drinking water has been limited to 10 µg/L by WHO. Many treatment technologies have been developed such as oxidation, lime precipitation, coagulation/filtration, adsorption, ion exchange and membrane processes to remove arsenic from water. Among these methods, adsorption method seems to be promising. Activated carbon is the most widely used adsorbent. Particularly, it can be obtained the most suitable adsorbents for different pollutants by modifying its surface properties. In this study; two magnetic activated carbons were prepared from almond shell, apricot and peach stones mixture and used for arsenic removal from aqueous solution. First activated carbon (MAC1) having 375.28 m2/g surface area and 0.2391 cm3/g of total pore volume was prepared from the mixture by direct FeSO4 chemical activation. The second one (MAC2) having 396.42 m2/g of surface area and 0.254 cm3/g of total pore volume prepared from a novel activated carbon prepared from the triple mixture by chemical activation with ZnCl2. Both activated carbons were used as adsorbent to remove the arsenic and effects of the some parameters such as pH, adsorbent dosage, contact time and initial arsenic concentration on the arsenic adsorption were examined. According to results obtained, it has been determined that pH, adsorbent dosage and contact time are important parameter affecting the arsenic adsorption onto both magnetic activated carbons. In order to remove arsenic ions having the concentration of 10 mg/L, the most suitable pH, adsorbent dosage and contact time have been determined as adsorbent dosage of 1.5 g/L and contact time of 60 min for MAC1, pH 4, adsorbent dosage of 1 g/L and contact time of 60 min for MAC2. Under these conditions, 99.31% and 100% of arsenic in the solution have been removed by MAC1 and MAC2, respectively.