Examination of gas and solid products during the preparation of activated carbon using phosphoric acid

Abstract

Activating agents play significant roles in the preparation of activated carbon (AC) from biomasses and their wastes, which are widely used in AC production. Application methods are also important for the production process. Products give remarkable ideas regarding the method and heat treatment process. The activated carbon was produced from waste tea in accordance with either the conventional method or microwave energy pretreated method using phosphoric acid (H₃PO₄) as activating agent. The yields of the activated carbons were 51.8% for conventional method and 46.0% for microwave pretreated method. The acid suppressed the formation of tar and promoted the amount of solid and aromatic structure accordance to sp² hybridisation. Additionally, the waste tea was directly carbonised (without H₃PO₄) and the yield was 36.3%. Major gas (H₂, CH₄, C₂H₆, C₂H₄, CO₂ and CO) products obtained during heat treatment process in a conventional furnace were examined in terms of quantity and quality. The solid products were characterised in terms of surface area, pore size and surface properties. The result of gas analysis showed that phosphoric acid affected formation of activated carbon mechanism and significant reactions occurred during microwave pretreatment process.

Keywords: Activated carbon; Characterisation; Chemical activation; Microwave pretreatment; Phosphoric acid; Waste tea.