The interaction mechanism between eggshell calcium and endogenous silica in biomass during biochar modification,and its impact on phosphate adsorption performance and slow-release fertilizer characteristics,remains un...The interaction mechanism between eggshell calcium and endogenous silica in biomass during biochar modification,and its impact on phosphate adsorption performance and slow-release fertilizer characteristics,remains unexplored.This study investigates that high silica content in biomass(>6%)inhibits the decomposition of CaCO_(3)in eggshells during pyrolysis,reducing the formation of active calcium species(CaO and Ca(OH)_(2)),while moderate silica levels(4%-5%)promote the formation of CaSiO_(3),enhancing phosphorus adsorption without hindering Ca^(2+)activation.Adsorption studies reveal that the precipitation of Ca_(5)(PO_(4))_(3)(OH)resulting from the combination of CaO and Ca(OH)_(2)with phosphate is the primary and effective form for phosphorus removal in calcium-modified adsorbents,accompanied by Ca_(3)(PO_(4))_(2)·2H_(2)O precipitation formed by CaSi O_(3).Eggshell calcium-modified corn straw biochar(ECS)exhibited the highest adsorption capacity,reaching 123.3 mg/g,outperforming materials in previous studies.ECS also demonstrated excellent pH adaptability and selective phosphate removal.As a biochar-based phosphorus fertilizer,ECS-P exhibits high phosphorus extractability in formic acid(93.92%)but low water solubility(0.62%),with phosphorus release during the seven-day intermittent leaching experiment remaining between 0.53 to 0.875 mg/L.These results confirm its potential as a phosphorus cycling fertilizer.This study provides fundamental insights into optimizing biomass selection based on silica content for calcium modification,offering an efficient strategy for both phosphate recovery and slow-release fertilizer development.展开更多
基金supported by Hebei Key Laboratory of Mineral Resources and Ecological Environment Monitoring(No.HBMREEM202302)Tianjin Key Research and Development Science and Technology Project(Nos.24YFXTHZ00170 and 24YFXTHZ00050)。
文摘The interaction mechanism between eggshell calcium and endogenous silica in biomass during biochar modification,and its impact on phosphate adsorption performance and slow-release fertilizer characteristics,remains unexplored.This study investigates that high silica content in biomass(>6%)inhibits the decomposition of CaCO_(3)in eggshells during pyrolysis,reducing the formation of active calcium species(CaO and Ca(OH)_(2)),while moderate silica levels(4%-5%)promote the formation of CaSiO_(3),enhancing phosphorus adsorption without hindering Ca^(2+)activation.Adsorption studies reveal that the precipitation of Ca_(5)(PO_(4))_(3)(OH)resulting from the combination of CaO and Ca(OH)_(2)with phosphate is the primary and effective form for phosphorus removal in calcium-modified adsorbents,accompanied by Ca_(3)(PO_(4))_(2)·2H_(2)O precipitation formed by CaSi O_(3).Eggshell calcium-modified corn straw biochar(ECS)exhibited the highest adsorption capacity,reaching 123.3 mg/g,outperforming materials in previous studies.ECS also demonstrated excellent pH adaptability and selective phosphate removal.As a biochar-based phosphorus fertilizer,ECS-P exhibits high phosphorus extractability in formic acid(93.92%)but low water solubility(0.62%),with phosphorus release during the seven-day intermittent leaching experiment remaining between 0.53 to 0.875 mg/L.These results confirm its potential as a phosphorus cycling fertilizer.This study provides fundamental insights into optimizing biomass selection based on silica content for calcium modification,offering an efficient strategy for both phosphate recovery and slow-release fertilizer development.
