Extraction of silica from sugarcane bagasse ash and its utilization in zeolite 4A synthesis for CO2 adsorption.

ABSTRACT

Sugarcane bagasse ash (SCBA) is a solid waste containing a high amount of silica (SiO2) and is suitable to utilize as a silica source for synthesizing zeolite NaA. SCBA is typically calcined at high temperatures before silica extraction. The method is not environmentally friendly because it consumes energy and produces CO2. This work demonstrates an alternative extraction method of SiO2 from SCBA by treating it with hydrochloric (HCl) and sodium hydroxide (NaOH) solution. The obtained mixture was separated by paper filter No. 1 (P) and a combination of paper filter and syringe filter (PS). The solution was neutralized by HCl solution, producing silica (SiO2-P and SiO2-PS) with a purity of 98 wt%. Both SiO2 samples and SCBA were utilized to synthesize zeolite NaA for CO2 adsorption. The CO2 adsorption capacities of NaA-P and NaA-PS were 4.30 and 4.10 mmol gadsorbent -1, in the same range as commercial NaA. The capacity is influenced by the total basicity of zeolite. The CO2 adsorption behavior of all samples correlates well with the Toth model. The CO2 adsorption kinetics agrees well with the pseudo-second-order kinetic model. Overall, this work shows the successful extraction of silica via using a direct NaOH solution, yielding high-purity silica sufficient for synthesizing zeolite NaA, a promising adsorbent of CO2.