Optimisation of physical and mechanical properties of a coffee parchment husk ash-based porcelain tile using response surface methodology

Abstract

Feldspar is a key component in the production of porcelain tiles. It is a fluxing material that decreases plasticity, permeability, and favors densification of the ceramic body. Coffee parchment husk ash (CPHA), a product from coffee processing was found to have fluxing oxides similar to those in feldspars. The main purpose of this study was to determine the optimal amount of CPHA that can be utilized to develop CPHA-based porcelain tile with feldspar being replaced by CPHA. Response surface methodology of design expert software was used for randomization studies. The independent variables were the portion of CPHA in feldspar (10-90 %) and firing temperature (800 -1200 0C). Other materials in the porcelain formulation were maintained at sand 10%, ball clay 20%, and kaolin 40%. The response variables were linear shrinkage (LS), water absorption (WA), and flexural strength (FS). The proportions were mixed, pressed at 40 MPa, and fired at their respective temperatures using a rate of 34 ℃/min. R2 values for LS, WA, and FS obtained were found to be above 94% implying that these factors had a strong relationship with the independent variables. The optimum conditions suggested by the developed model were 10% of CPHA and 1197 ℃ firing temperature with responses of LS 7.97%, WA 0.03%, and FS 37.63 MPa. The confirmatory experiment carried out, obtained LS 8.15%, WA 0.11%, and FS 38.32 MPa. These findings confirm that the prediction model was accurate. These test values of the tiles 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 and other ceramic products. Adoption of CPHA in ceramics production can contribute to reductions in the cost of maintaining landfills as well as the cost of acquiring feldspar for production.