Application Research Of Biomass Ash Preparation For Soil Improvement And Fertilizer Slow-release Materials

Biomass ash is a mixture of various wastes produced by biomass power generation,and it is difficult to be effectively used because of the complex composition.At present,the treatment of biomass ash is mainly landfill,which not only consumes a lot of land resources,but also causes great harm to the ecological environment and residents’health.Notably,biomass ash has strong alkalinity,which greatly limits its application area for resource utilization.Therefore,it is crucial to achieve cost-effective and environmentally friendly large-scale digestion of biomass ash.Humic acid is an inexpensive natural macromolecular organic acid material.It has been found that humic acid compound fertilizer prepared by multiple processes such as extraction and acidification can promote the growth of crops.However,due to the relatively complex and costly preparation process,the marketable application of humic acid compound fertilizer is greatly restricted.To solve above problems,humic acid was used as a neutralizer of biomass ash for the preparation of environmentally friendly biomass ash/humic acid soil amendment materials（BAHA）.According to this,the sample BAHA-O under the best process conditions was also selected for the study of adsorption-slow release performance,and the biomass ash/humic acid fertilizer slow release materials（BAHA-LRC）were prepared as a carrier of nitrogen and phosphorus.The effects of BAHA-O and BAHA-LRC on soil improvement and cabbage growth were investigated to provide more reliable scientific basis for the resource utilization of biomass ash in soil improvement and low-cost preparation of BAHA-LRC.The main content of this paper is summarized as follows:1.Humic acid is used to neutralize strong alkalinity of biomass ash and activate nutrients in biomass ash.Using the Box-Behnken experimental design method and following the p H requirement of compound fertilizer in the national standard,the optimal experimental parameters for the reaction between biomass ash and humic acid were determined as follows:reaction temperature T of 120°C,reaction time t of 2 h,and reaction ratio k of 2.The p H of the sample BAHA-O prepared under these conditions was 7.81±0.12.In addition,the characterization and test analysis of BAHA prepared under different conditions revealed that the content of nutrients such as available Si,available K,available P and pore structure in BAHA increased significantly with the increase of reaction temperature and reaction time.2.Benefiting from the rich pore structure,BAHA-O is used as a slow-release material for nitrogen and phosphorus.The adsorption-slow release ability of BAHA-O on NO₃^-,NH₄⁺and PO₄^3-was investigated by adsorption-slow release experiments.When the temperature was 298 K,the amount of adsorbent was 2.5 g/L and the p H was7,the maximum adsorption amounts of BAHA-O for NO₃^-,NH₄⁺and PO₄^3-were 5.32mg/g,3.01 mg/g and 3.86 mg/g,respectively.The adsorption isotherms of BAHA-O for NO₃^-,NH₄⁺and PO₄^3-were basically in accordance with the Langmuir model,and the adsorption kinetic curves were basically in accordance with the proposed secondary kinetic and intraparticle diffusion models.In addition,the desorption rates of BAHA-O for NO₃^-,NH₄⁺and PO₄^3-were basically stable at 70%-80%.3.Based on the rich nutrients,abandunt pore structure and better adsorption-slow release ability for nitrogen and phosphorus,BAHA-O and BAHA-LRC were applied to soil improvement and cabbage growth.BAHA-LRC was mixed with soil for leaching experiments,and it was found that BAHA-LRC could significantly reduce the leaching of nitrogen and phosphorus from the soil.BAHA-O and BAHA-LRC were mixed with soil for cabbage pot experiments to investigate the effects of BAHA-O and BAHA-LRC on soil physicochemical properties,nutrient composition,cabbage yield and nutrient uptake,respectively.The results showed that BAHA-O and BAHA-LRC treatments significantly increased the contents of EC,CEC,total organic carbon,total N,total P,total K,available P and available K in the soil,and significantly improved the soil SWA and bulk weight.Meanwhile,BAHA-O and BAHA-LRC treatments significantly increased the fresh weight of cabbage as well as the content of total N,total P,total Si,chlorophyll a and chlorophyll b in cabbage.In addition,compared to BAHA-O treatment,BAHA-LRC treatment had more significant promotion effect on soil nutrients and yield of cabbage.