Sustainable conversion of Brazilian Amazon kaolin mining waste to zinc-based Linde Type A zeolites with antibacterial activity

Green and low-cost synthesis of zeolites from kaolin: a promising technology or a delusion?

“…11b). This proportion does not agree with the one obtained by Schwanke et al 111 It implies that, even in completely X-ray amorphous metakaolin, changes associated with an increase in Al IV amount can still occur with increasing temperature. It may be due to the removal of residual hydroxyl groups since it has been reported that the amount of Al IV is highest at the maximum degree of dehydroxylation.…”

“…11a). 111 The kaolin sample contained only aluminium in octahedral coordination (Al VI ). The metakaolin was completely X-ray amorphous.…”

“…54 The fact that attempts to synthesise LTA without metakaolinisation always yield SOD indicates that kaolinite is more stable than LTA under equal conditions. 111,132 So, the intermediate phase before SOD does not form.…”

“…21 The process time also varies. Usually, metakaolinisation is carried out in a muffle furnace for 2 h, 72,80,111 but there are studies where it has been carried out for 8 h. 70 Metakaolinisation in a microwave oven can reduce the process time to half an hour. 85,88,143 In our opinion, the main problem with metakaolinisation is that researchers often do not explain the choice of temperature and time.…”

Utilization of silica-enriched filter cake industry by-products as partial ordinary portland cement replacement

“…The presence of anatase in filter cakekaolinite is widespread owing to the geological location where the clay is mined, and it is regarded as an impurity in the finished product. Some of the investigations have found impurities such as Fe, Ti, and Al minerals in these clays [30,31]. One of the main minerals of clay illite was also observed at 2θ angles 23.05, 29.8, and 47.4.…”