Beneficiamento de uma argila tipo paligorskita da bacia de S. Luis-Grajaú, região de Alcântara, MA, e sua utilização como adsorvente de fósforo

Abstract

This study used a sample from the basin of S. Luís-Grajaú, Maranhão state, Brazil,consisting of a mixture of predominantly palygorskite and dolomite, approaching the existence of this new occurrence, suggesting a processing method and its application as phosphorus adsorbent, once dolomite is a pH soil corrector while palygorskite has the function of nutrients carrier. First, chemical and mineralogical characterizations were performed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and separation of sand, silt and clay fractions. Sedimentation and phosphorus adsorption experiments were also performed, with determination of kinetic curve. After the X-ray diffraction analysis, results show that the sample consists mainly of palygorskite and dolomite. Illite, chlorite and quartz are also determined. It was also possible to see that the different types of disaggregation used show no significant differences in the diffraction patterns of the samples. The sand-silt-clay separation, although it is only based on the size of the material, showed a reasonable efficiency for material separation, as the sedimentation tests, where it was noticed that after 24 h, dolomite had disappeared from the supernatant. Determination of the kinetic curve revealed that the adsorption period of 2 h is not sufficient for phosphorus adsorption, requiring 24 h to reach the reaction equilibrium. Sorption tests showed efficiency higher than 91% of the initial phosphorus in solution, and the maximum quantity adsorbed per gram of sample was 0.607 mg. The correlation with the adsorption isotherm models studied, showed better results for Langmuir-Freundlich isotherm, with correlation coefficient of 0.9993, which can be attributed to the fact that adsorption occurs in more than one layer.