Isolation and Selection of Halophilic Ureolytic Bacteria for Biocementation of Calcium and Magnesium from Seawater

Abstract

Antofagasta the second region of Chile is known worldwide for its extensive mining activity, mainly in the production of copper, molybdenum, iodine and lithium. It is also one of the driest areas of the world with few sources of fresh water that in addition to the current increase in the development of mining projects, it has generated a strong necessity for sea water uses in industrial processes. Recently some mining companies are evaluating the use of seawater in various processes, including mineral flotation. However, they have determined a low metallurgical recovery mainly of Mo, due to the effect of secondary ions as calcium, magnesium, sulfate and bicarbonate present in sea water, which precipitate at alkaline pH and produce colloids that interfere in flotation.As a biotechnology alternative to increase the recovery of valuable species by flotation in seawater, it has been isolated and characterized selected native halophilic bacteria in the Atacama Desert, which used urea as a source of energy to produce ammonia and CO2. The ammonia increases the pH of carbonate generating means, which provides favorable conditions for the formation and precipitation of Ca and Mg carbonates and secondary ions presented in high concentration in seawater.The results show that from the total isolates, 22% has proven urease activity by the method of Christensen and phenolphthalein. Furthermore, isolates were evaluated for their ability to precipitate these ions by biocementation assay. Those bacterial isolates that precipitate these ions faster were identified phylogenetically and urease activity and microbial kinetics were quantified. Finally the obtained crystals were subjected to electron scanning microscopy and X-ray diffraction determining the morphology of the crystals production and mineralogical composition.