Recovery of silica from aluminum sulfate byproduct and its application as filler for rubber industry

Abstract Resource recovery from byproducts of chemical manufacturing is essential for environmental sustainability promoting circular economy. In this study, amorphous precipitated silica, filter cake silica (FCS), from filter cake byproduct of Awash Melkassa Chemical Factory is prepared, and its potential as a rubber filler in the tire industry is explored. The filter cake byproduct is calcinated at 550 °C for 3 h, followed by extraction of FCS using acid leaching followed by sol–gel process. AAS, XRD, XRF, FTIR, SEM, and BET are employed to characterize the phase composition, chemical structure, morphology, and surface area of the prepared silica. Silica, FCS, with a purity of 92.5% is achieved and the curing and mechanical properties of unfilled, FCS‐filled, and commercial silica (COS)‐filled rubbers are analyzed. The FCS‐filled compound exhibits shorter curing time of 229 s and lower Mooney viscosity of 58.15 ± 0.42 M.U compared to the COS‐filled rubber compound. In addition, superior mechanical properties such as tensile strength of 19.52 ± 1.28 MPa was exhibited by the FCS‐filled rubber compound due to the finer particle size and high surface area of the filter cake silica compared to the COS filled rubber compound (17.94 ± 1.99 MPa) as well as the unfilled rubber. Therefore, recovery of silica from the byproduct filter cake offers a promising role as filler in the tire industry in addition to serving as a potential waste management solution for Awash Melkassa Chemical Factory and related industries.