Applied Basic Research Phosphorus Slag Leachate

Yellow phosphorus slag is a solid waste which is formed by water quenching of high temperature slag in the course of producing yellow phosphorus with electrical furnace and consist of large amounts of silicon and calcium element, is an amorphous solid materials with higher activities. It is a secondary resource that can be used for preparing silicon and calcium with high added value products. This paper study the distribution of impurity elements and precipitation crystallization dynamics of calcium in the process of precipitating calcium ion in the nitric acid lixivium by sulphuric acid solution and recycling process of lixiviumThe experimental study indicated that the optimum process conditions of precipitating Ca2+in lixivium of yellow phosphorus slag by sulfuric acid solution to obtain of CaSO4products is that sulfuric acid concentration is20%, the reaction temperature is room temperature, volume ratio of H2SO4and HNO3lixivium is0.6:1, the reaction time is45minutes, drying temperature250±5℃. The yield of CaSO4reaches92.52%, the purity is99.09%, the sample is anhydrous CaSO4, morphology was whisker and appearance is white under the optimum process conditions. More than95%MgO,96%Al2O3,91%Fe and98%F in impurity elements of nitric acid lixivium remain in the liquid phase in the process of precipitating calcium ion in the nitric acid lixivium by sulphuric acid solutionThis paper studied precipitation conversion process of nitrate calcium in lixivium by batch dynamic method. The research showed that the size distribution of calcium sulfate crystal precipitated with sulfuric acid in20to180microns is about97%of the total crystal. The precipitation conversion process of calcium in lixivium was a batch dynamic process and can be described with grain number balance equation of batch dynamic process treated by the transformation method of moments. The nucleation and crystal growth kinetics equations of precipitating calcium in lixivium was obtained by treated experimental data with the moments transformation method of batch dynamic process.When the calcium in nitric acid lixivium of yellow phosphorus slag was precipitated with sulfuric acid solution and the lixivium after precipitation conversion was recycled for leaching yellow phosphorus slag, the study indicated that the time of recycling can reach more than10times. The nitric acid lixivium after recycling which was treated by neutralizing to remove the cumulative iron, aluminum and other impurities can be used for recycle of leaching yellow phosphorus slag again, the time of recycling can also be reached more than10times and the quality of white carbon black samples is basically the same as first time recyclingThe purity of white carbon black obtained in the course of cyclic process is more than98%, whiteness are above85%. The SEM analysis indicated that samples are irregularity amorphous particles and surface is rough. The content of calcium sulfate calcium(CaSO4·2H2O) products obtained in the process of recycling lixivium is99.69%and whiteness is96.96%.Finally, the paper studied application of residue obtained in the process of removing impurities from cyclic lixivium. Experimental results showed that the residue obtained from purifying cyclic lixivium may be used as water treatment agent and the removal rate of phosphorus in the wastewater can reach74.69%, the turbidity removal rate reached97.55%. Process conditions of wastewater treatment are that wastewater was200mL, room temperature, pH7, the adding amount of flocculant3g. The mechanical analysis indicated that the residue obtained has larger differential particle size distribution and accounts for about60%in50-100microns.