Feasibility Study on Release Rate of Phosphorous and Trace Elements from Basaltic Glass by Using Batch Reaction Experiments

Abstract

The production of world phosphate rock might reach to its peak before mid-century due to the potential demand for phosphate fertilizer consumption especially in developing countries, and as a result this could eventually lead to depletion of well-known easily exploitable reserves worldwide during the following decades. The slow natural-mineral fertilizer may be one possible strategy to meet the future possible lack of cheap and high-P sources. For this I investigated to what extant basaltic glass has enough capability to provide sufficient amount of nutrients, especially phosphate, for the food production in future. This was done by performing batch reaction rate experiments and MATLAB simulations. In this study the effect of grain size and temperature on basaltic glass dissolution has been studied using batch reaction (closed system) at 50oC and 90oC. The result shows that dissolution rate of basalt glass increases with the decreasing grains size and also by increase of temperature. The effective size of gains for dissolution rate were identified by using an ideal condition reaction (i.e. Matlab simulations), where found that very fine particles fraction (i.e. <1.5 µm diameter) are dissolving efficiently at 10oC throughout year and can last for several years. The high-temperature experiments showed that phosphate was effectively removed from the solution, probably by sorption to secondary clays, oxides, and/or hydroxides formed during the experiment. A clay phase, probably smectite, is forming on the grains surface at 90 oC. The release rates of nutrients at 10 oC, suggest that the amount of phosphate required as a fertilizer is more than 400-500 Kg/ha/year, whereas if basalt is also used as a nitrate source, the amount of basalt required for these elements are 930 and 1852 Kg/ha/year respectively. Continuous supply of phosphate and nitrate can be ensured by taking some necessary actions like proper use of grain size fraction (e.g., finer grains) and pretreatment of basalt etc., to reduce sorption in the soils.