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Extraction of Caustic Potash from Coffee Husk: Process Optimization Through Response Surface Methodology

A. Kumar

The work investigates ashing of coffee husk and leaching of potassium carbonate from ash as a potential as a source for potassium. The husk was ashed and analysed for ions. It was found that the ash contains a significant amount of alkali metals. Ashing temperature influenced the yield of potassium carbonate, the most predominant alkali in ash. Potassium carbonate was leached from ash by water as a solvent. Variables affecting the yield are the ashing temperature, ash particles size, stirring, and solvent temperature. A 23 Factorial design with centre point for experiment design and Response surface methodology was used to study the effect of ashing temperature, ash particle size, and the leaching temperature, which were identified as the key variables. Ash had 71.5 wt. % K when analyzed for alkali metals, and 15.2 wt. % potassium carbonate. Maximum ash yield of 18 wt% was at ashing temperature of 400-500o C. For leaching of carbonate, optimum ashing temperature was 600o C, smallest particles size (40-200 μm), and high solvent temperature (70o C).