Sorptive removal of Arsenic from aqueous solution using activated carbon produced from coffee husk

Abstract

Nowadays, arsenic removal from water is a major problem in many parts of the world. As recent studies document, groundwater from Ethiopian rift valley is also under the risk of arsenic contamination. Exposure to high level of Arsenic have been shown to cause acute health effects such as nausea, vomiting and abdominal pain. Long-term exposure to Arsenic is known to increase the risk of chronic diseases such as lung, skin, kidney, urinary and bladder cancers. The general objective of this study was to investigate removal of arsenic from aqueous solution by adsorption using activated carbon derived from coffee husk. In this study, batch adsorption experiments were conducted to examine the As (III) adsorption capacity of chemically activated coffee husk as the function of contact time, pH of the solution, initial Arsenic concentration, adsorbent dose, agitating speed, adsorbent particle size and desorption study parameters were investigated. The study showed that adsorption capacity increased with increasing time and equilibrium time reached 60 min maximum adsorption percentage was 56%. The adsorption of As was greatly dependent on pH of the solution. Generally, adsorption was remained that with increasing solution pH percent removal also increased. The amount adsorbed and percentage removal of As (III) was increased from 0.75 to 1.68 mg/g and 24.95% to 56% respectively as the amount of activated carbon was increased from 0.5 to 4 g. As initial As (III) concentration increases As (III) removal efficiency decreased from 79.8(%) to 43.9(%).The equilibrium adsorption data were better represented by the Freundlich isotherm (R2 = 0.9649). The adsorption kinetics data of As adsorption followed well the pseudo-first order equation with the correlation coefficient R2 = 0.96 and Kf = 0.087. The desorption experiment done using alkaline solution of 0.1M and 0.3 M of NaOH and desorption capacity was increased from 52.5% and 71.4% respectively. Thus chemically activated coffee husk could be used as a media for removal of arsenic from aqueous solution and the spent CACH can be regenerated and reused as desorption study reveals.