Dye removal from aqueous solution with activated carbon obtained from biomass

In addition to the convenience that the development of technology has brought to our lives, the amount of pollution caused by industry is rapidly increasing daily, putting a strain on nature and the environment. The increasing pollution of our ecosystem has become a major threat to natural resources and human health. Water pollution occupies an important place among these pollutions. Activated carbon is an adsorbent widely used for wastewater treatment, drinking water treatment, the pharmaceutical industry, metal removal, the food industry, gas purification and air pollution removal without separation. In our country, the variety of biomass that can be used as a raw material for producing activated carbon is very large. In particular, activated carbons produced from low-cost waste are very important to convert biomass with low material value into high-added-value products in a renewable and efficient way. In this study, activated carbon was prepared from biomass (walnut shell) with the chemical activation of H3PO4 at different impregnation rates and activation temperatures, and the characterization of the activated carbons prepared by different methods was performed. Through coarse and size analysis of biomass, a size range of 0.6-0.8 mm was used to produce activated carbon. The carbonization temperature (400, 500, 600 °C) and chemical impregnation ratio (2/1, 3/1, 4/1), which are the most important parameters in the chemical activation method, affect the SBET surface area, pore volume, pore size distribution, and average pore size of the activated carbons. The effects on surface properties, such as diameter, were investigated. It was found that the surface area increased from 793 m2/g to 1328 m2/g when the chemical impregnation ratio was increased from 2:1 to 4:1. A decrease in surface area was observed when the temperature was increased from 400 °C to 600 °C at all impregnation rates. Activated carbon with the highest surface area (SBET; 1328 m2/g) obtained from the walnut shell was produced at a 4:1 impregnation ratio and a carbonization temperature of 400 °C. It has been used in the removal of Malachite Green by the activated carbon adsorption method with an area of 1328 m2/g. Parameters affecting adsorption (pH, adsorbent dose, contact time and temperature) were investigated. The study carried out adsorption kinetics, isotherm, regeneration and thermodynamics (∆H°, ∆S°, ∆G°) studies. Activated carbon with the highest surface area was used to remove Malachite Green by adsorption from the aqueous solution. In removing malachite green dye with activated carbon, the adsorption kinetics obey the so-called second-order equation, and the equilibrium isotherm obeys the Langmuir equation. The results revealed that activated carbons with high surface area and pore structure could be produced from walnut shells and used in malachite green adsorption.