Molecular dynamics studies of hematite surfaces with PAM, HPAM and metasilicate

Abstract

In the search to improve the obtaining of iron ore, different additives have been proposed to improve this activity. A deeper study is necessary to understand the affinities of different additives on iron ore and thus be able to search for or synthesize new additives according to the desired objective. In this work, the affinities of the iron mineral represented by the hematite crystal on the neutral 001 surfaces at pH ~9 are studied by molecular dynamics methods, in the presence of waters with low salinity and high salinity. The additives to be studied are a sodium metasilicate dispersant, a neutral polyacrylamide (PAM) flocculant, and 25% anionic polyacrylamide (HPAM). The study considered the calculation of the minimum distance between the surface and the additives. The results show that the affinity of the metasilicate is high with the surface. In the case of PAM polymers, their adsorption decreased as the number of salts increased. In the case of HPAM, the adsorption is greater than in PAM and improved with the addition of salts. This indicates that hematite is a surface with a high local charge density that attracts charged groups such as metasilicates and HPAM. the neutral PAM polymer is adsorbed but to a lesser extent due to its neutrality. The presence of salts indicates that there is competition for adsorption on hematite with respect to PAM, but that the salt is beneficial to HPAM due to the formation of cationic bridges. These results will help in the search for additives for the concentration or dispersion of iron ore.