Study On Agricultural Resource Utilization Of Silicon Calcium Slag By-product Of Aluminum Extraction From High Aluminum Fly Ash

Under the realistic background that China's high-quality bauxite resources are about to be exhausted and human dependence on aluminum products is rising year by year,industrial production of alumina extraction with high-aluminum fly ash material is increasing.At the same time,The output of silicon-calcium slag,the end product of aluminium extraction process,also increased synchronously.The large-scale consumption of silicon-calcium slag has become an urgent problem to be solved in the high aluminum fly ash aluminum industry.The main component of siliceous calcium slag is dicalcium silicate,which is rich in silicon and is a good source of silicon fertilizer.Based on the utilization of solid waste resources,this paper aiming at the synergistic utilization of aluminium and silicon resources in high aluminum fly ash,the experiment of extracting aluminium from high aluminium fly ash and co-producing silicon-calcium slag was carried out,and explored the feasibility of agricultural application of silicon calcium slag.Firstly,alumina was extracted from high alumina fly ash by soda lime sintering method.The chemical composition,purity and phase composition of the product alumina and siliceous calcium slag were analyzed by XRF,XRD and SEM.Then,silicon release experiments were carried out to study the release of silicon from high alumina fly ash,laboratory aluminum silicon-calcium slag and Datang aluminum silicon calcium slag.Finally,the pot experiment was conducted to study the improvement effect of high aluminum fly ash,laboratory silicon calcium slag and Datang silicon calcium residue on acid red soil in South China,and plant height,yield,chlorophyll content,vitamin C content,calcium and magnesium content and absorption of celery,and heavy metal content.To evaluate the applicability of silicon-calcium slag as silicon fertilizer.The results show that the alkali lime sintering method used in the laboratory has a good effect in extracting aluminium from high aluminium fly ash.The extraction rate of Al₂O₃reaches 93.86%,and the purity of Al₂O₃ products reaches 97.94%.silicon-calcium slag,a by-product of aluminium extraction,is amorphous with dicalcium silicate as the main component and 24.02%effective silicon content.The parameters b and k in Freundlich equation and Elovich equation reflect the release of silicon,and can be used to measure the silicon release ability of fly ash and silicon-calcium slag.In the two extracts,the order of silicon release amount and release rate is:Tang silicon-calcium slag>laboratory silicon-calcium slag>high alumina fly ash.The application of silica-calcium slag could significantly increase the pH value of acid red soil,supplement the mineral nutrient contents of Ca,Mg and Si,and improve the acid red soil to a certain extent.High alumina fly ash inhibited celery growth to some extent,while silicon-calcium slag promoted celery growth.The plant height of celery treated with 0.5-2 g/kg silicon-calcium slag was increased by 5.15-14.22%,and the yield of celery treated with 0.5-3 g silicon-calcium slag was increased by 17.48-50.08%.The content of chlorophyll and vitamin C in celery could be increased to a certain extent by applying high-alumina fly ash and silicon-calcium slag,and the lifting capacity of silicon-calcium slag was higher than that of high-alumina fly ash.When the dosage of 2 g/kg was applied,the chlorophyll content of laboratory silicon-calcium slag and Tang silicon-calcium slag reached the highest,which were15.00%and 16.04%higher than the control respectively.When the dosage was 3 g/kg,the content of vitamin C in celery leaves and stalks from laboratory and datang silicon calcium slag reached the highest,and the content of vitamin C in leaves was 1.81¹.86 times higher than the control.The content of vitamin C in culm was 2.67².77 times higher than that in control group.The application of silicon-calcium slag can effectively promote the nutrient absorption and improve the nutritional quality of celery.Compared with CK,the contents of calcium and magnesium in celery increased by 2.74%¹7.10%and 22.80%⁵7.31%respectively,and the absorption of calcium and magnesium increased by 14.79%⁸0.47%and44.82%¹14.51%respectively.Appropriate amount of silicic calcium slag and fly ash will not increase the heavy metal hazard of the crop,and vice versa,and also reduce the Pb and Cr content in celery,and have certain safety guarantees for agricultural applications.Studies have shown that siliceous calcium slag is better as a silicon-calcium fertilizer and can be widely used in farmland in the future.