Optimization of physical and mechanical properties of porcelain tiles from coffee parchment husk ash

Coffee parchment husk ash (CPHA), a product from coffee processing was found to have similar fluxing oxides as are found in feldspars. CPHA is produced in large quantities through the combustion of coffee parchment in industries to produce energy for drying purposes. CPHA is commonly disposed of in landfills and open fields, causing pollution to the environment and ecosystems. In this work, response surface methodology (RSM) was used for optimization of porcelain tile bodies in which the portion of CPHA in feldspar was varied from 10 to 90 wt% and firing temperature from 800 to 1200 ℃. The response variables were linear shrinkage (LS), water absorption (WA), and flexural strength (FS). Other materials in the porcelain were maintained at 10 wt% sand, 20 wt% ball clay, and 40 wt% kaolin. Mixed proportions were dry pressed at 40 MPa and fired to respective peak temperatures at a rate of 34 ℃/min. The optimum conditions obtained were 10% of CPHA in feldspar and 1197 ℃ firing temperature. Validation experiments presented LS 8.15%, WA 0.11%, and FS 38.32 MPa. These values agree with optimum responses from RSM and therefore confirm the accuracy of developed prediction models. The test values lie within the range specified by 1SO 13006:2018 for porcelain floor tiles. These findings demonstrate that CPHA can be used as a raw material for production of porcelain floor tiles. Adoption of CPHA in ceramic production can contribute to reduction in the costs of maintaining landfills.