Hydroxyapatite/Dolomite alkaline activated material reaction in the formation of low temperature sintered ceramic as adsorbent materials

Abstract

Hazardous pollutants, especially heavy metals in wastewater, have become a major concern due to the high potential of causing serious problems to humans and aquatic ecosystems, such as adverse health effects, environmental damage, and air pollution. The adsorption process is widely used to remove heavy metals because it is inexpensive, simple, and environmentally friendly. However, recent studies have shown that some adsorbents such as activated carbon, ion exchange resins, and carbon nanotubes are becoming more expensive due to their complex production. Considering these problems, alkali-activated materials (AAMs) can be considered as a new potential adsorbent material due to their excellent physical, chemical, and mechanical properties, which make them suitable for use in the field of civil engineering. Dolomite is one of the AAMs that is capable of adsorbing hazardous pollutants such as heavy metals in wastewater due to its unique structure. This material is also classified as a cost-effective adsorbent because it is abundant and can be found all over the world. Nevertheless, few studies have focused on the adsorption method using dolomite as a precursor material to remove heavy metals in wastewater, and currently only limited studies focus on the relationship between dolomite and hydroxyapatite (HAP). In addition, some studies have shown that the properties of geopolymers can be improved (up to 40%) when a moderate amount of calcium-containing material is added to the geopolymer. Although they have been used as a stand-alone material with excellent properties, combining them with another material could be another way to improve their properties. Therefore, this review provides an in-depth analysis on the properties of dolomite as a new potential precursor material in combination with HAP for contaminant removal. This would help to find the best parameters for the geopolymerization process between dolomite and HAP to meet the adsorption method requirements. This paper also investigated the ability of HAP as a carrier with the combination of bacterial strains via an immobilization process to improve the properties of dolomite as a geopolymer adsorbent. A microbial community can also act as an adsorbent for the removal of heavy metals and inorganic/organic contaminants from wastewater. This review can serve as a basis for understanding the ability of dolomite/HAP as a new alkali-activated material in geopolymer adsorbents in combination with immobilizing bacteria to remove heavy metals in wastewaters.