Abstract
Activated carbons were obtained from cocoa pod husk using two different initial particle sizes (ranges 0.25 – 0.50mm and 0.50 – 1.00mm), three chemical activation agents (K2CO3, KOH and ZnCl2) and carbonization under nitrogen atmosphere during two hours at three different temperatures (500°C, 650°C and 800°C). The prepared activated carbons were characterized using Brunauer–Emmett–Teller (BET) and Langmuir surface areas, pore volume, average pore size, bulk density, moisture, ash content, and yield. The five best activated carbons were selected for further experiments according to the chemical activation agent used, high BET surface area, high pore volume and low ash content. Additionally, content of impurities, carbon content and FE-SEM micrographs were determined for these five best activated carbons. As adsorption tests were also carried out with these samples. Results of the experiments show that cocoa pod husk is a material that can be used to produce activated carbon by chemical activation and ZnCl2 showed to be the best chemical activation agent based on the highest BET surface area (780 m2/g in the best case) and pore volume (0.58 m3/g in the best case), the lowest ash content (6.14% in the best case), and the highest carbon content (86.1% in the best case), compared with others chemicals. Carbons activated by ZnCl2 are capable to adsorb As(V), getting As(V) removal levels up to 80% in less than 1 hour in the experimental conditions applied (initial pH 6-7, activated carbon concentration 0.1 g/l and 0.5 g/l, initial As concentration 100 ppb).
Highlights
Adsorption with activated carbon is a useful treatment method to remove pollutants from waters and wastewaters
Commercial activated carbons are expensive and it is important to find out new low cost materials available for use as adsorbents
This study aims to produce a low-cost activated carbon from cocoa pod husk using three different chemical activation agents, three different carbonization temperatures and two different particle sizes of the raw material
Summary
Adsorption with activated carbon is a useful treatment method to remove pollutants from waters and wastewaters. Commercial activated carbons are expensive and it is important to find out new low cost materials available for use as adsorbents. In Peru agricultural wastes as cocoa pod husk are disposed in unsuitable conditions, generating bad smell, microorganisms, pollution of water stream and considerable impacts on the landscape. Another advantage from the environmental point of view is that cocoa pod husk may be considered as a renewable resource because it has been replenished continuously
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