Enhanced mechanical strength of micro-porous ceramics through the removal of alkaline earth carbonates from Moroccan red clay for membrane support application

The influence of the removal of carbonates on the ceramic properties made of Moroccan red clay as a main material and tea waste as pore-forming agent, has been investigated. ATD-TG, dilatometry, dimensional changes, weight loss, water absorption, open porosity, bulk density, flexural and indirect tensile strengths were assessed at different firing temperatures within the range of 900-1150 degrees C. SEM was used to evaluate the microstructures of the fired samples, while XRD was used to study the phase evolution. At varying firing temperatures, the materials which contains the carbonate (CC) exhibit greater weight loss, water absorption, and porosity compared to the materials without carbonate (NCC). On the other hand, NCC materials has greater mechanical strength than that CC materials. The microstructural analysis conducted through SEM revealed distinct changes in the fired samples when comparing observations at 1100 degrees C to those at 900 and 1000 degrees C. At 1100 degrees C, there was a noticeable increase in particle contacts and layered structures, which can be attributed to the presence of dehydroxylated clay minerals (illite and chlorite), quartz particles, and pores formed during firing. Subsequently, at 1150 degrees C/ 2 h, further alterations in the microstructures were observed due to a higher degree of vitrification in the fired samples. This resulted in material consolidation, interparticle and neck contacts, leading to the formation of vitrified bridges. Firing has resulted in the formation of closed and open pores of varying sizes, in the vitrified structures associated with anorthite, hematite, and quartz, a thin crystal precipitation of small particles was observed. This alteration in microstructure made it possible to conclude that the flexural and indirect tensile strength increased during firing, reaching its pinnacle at 1150 degrees C. As a result of the firing process, the ceramic supports underwent heightened sintering, leading to a gradual decline in open porosity. The present inquiry proved to be intriguing as it led to a deeper understanding of the utilization of Moroccan red clay as a ceramic's raw material.