棉秆生物炭脱除餐厨沼液氮磷性能研究

Nitrogen and Phosphorus Removal Performance of Cotton Stalk-derived Biochar for Kitchen Waste Biogas Slurry

摘要:

为探究棉花秸秆生物炭净化餐厨沼液、回收氮磷养分的可行性,明晰热解温度对炭吸附性能的调控规律,本研究以棉花秸秆为原料,在不同热解温度(300、400、500、600、700℃)下制备棉秆生物炭,系统表征其理化结构,考察其对模拟沼液中氨氮、硝氮、总氮、总磷和COD(本文COD特指以化学方法测定需要被氧化的还原性物质)的吸附性能,并以综合性能最优的生物炭为吸附材料,开展投加量梯度试验,探究其对实际沼液中污染物的去除效果与有效添加量阈值。结果表明,热解温度对生物炭的理化性质与吸附行为具有显著调控作用。600℃制备的生物炭对氨氮和COD吸附效果最优,单位吸附量分别为8.65mg/g和181.02mg/g;500℃制备的生物炭对硝氮和总氮去除性能最佳,单位吸附量分别为27.0mg/g和68.66mg/g;700℃制备的生物炭对总磷吸附性能最优,单位吸附量达3.36mg/g。500℃制备的生物炭虽非所有污染物吸附性能单项最优,但其综合吸附能力最为均衡,兼具发达的孔隙结构与适宜的含氧官能团,可作为实际沼液处理的优选材料。吸附动力学分析表明,氨氮、硝氮、总氮与COD的去除以物理吸附为主导,符合准一级动力学模型;总磷的去除则以化学沉淀与络合作用为主,符合准二级动力学模型。在实际沼液应用中,随着优选生物炭添加量由1g增至2g,各污染物去除率持续上升,单位吸附量呈下降趋势。当添加量达到1.5g时,各污染物去除率提升幅度显著减缓,表明该体系下的有效添加量阈值为1.5g。综合吸附性能与材料经济性,500℃制备棉秆生物炭在添加量1.5g条件下,在沼液吸附处理中具有良好的工程应用潜力。

Abstract:

Aiming to explore the feasibility of using cotton stalk biochar for purifying kitchen waste biogas slurry and recovering nitrogen and phosphorus nutrients, and clarify the regulatory role of pyrolysis temperature on the adsorption performance of biochar, it prepared cotton stalk biochar at different pyrolysis temperatures (300℃, 400℃, 500℃, 600℃, and 700℃). The physicochemical structures of the biochar were systematically characterized, and its adsorption performance for ammonia nitrogen, nitrate nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand ( COD specifically referred to the amount of reducing substances determined by chemical oxidation) in simulated biogas slurry was investigated. The biochar with optimal comprehensive performance was selected for dosage gradient experiments to explore its removal efficiency of pollutants from actual biogas slurry and determine the optimal dosage threshold. The results indicated that pyrolysis temperature significantly regulated the physicochemical properties and adsorption behavior of the biochar. Biochar prepared at 600℃exhibited the highest adsorption capacity for ammonia nitrogen and COD, with values of 8.65mg/g and 181.02mg/g, respectively. Biochar prepared at 500℃ demonstrated the best removal performance for nitrate nitrogen and total nitrogen, with adsorption capacities of 27.0mg/g and 68.66mg/g, respectively. Biochar prepared at 700℃ showed the highest adsorption capacity for total phosphorus, reaching 3.36mg/g. Although biochar prepared at 500℃ was not the optimal adsorbent for any single pollutant, it possessed the most balanced comprehensive adsorption performance, characterized by welldeveloped pore structure and suitable oxygen-containing functional groups, making it a promising candidate for the treatment of actual biogas slurry. Kinetic analysis revealed that the removal of ammonia nitrogen, nitrate nitrogen, total nitrogen, and COD was dominated by physical adsorption, consistent with the pseudo-first-order kinetic model, whereas the removal of total phosphorus was primarily governed by chemical precipitation and complexation, fitting better with the pseudo-second-order kinetic model. In the application to actual biogas slurry, as the dosage of the optimal biochar increased from 1g to 2g, the removal rates of all pollutants continued to increase, while the adsorption capacity per unit mass decreased. When the dosage reached 1.5g, the increase in removal rates slowed significantly, indicating that the optimal dosage threshold for this system was 1.5g. Considering both adsorption performance and material economy, the biochar prepared at 500℃ demonstrated good engineering application potential for the adsorptive treatment of biogas slurry at a dosage of 1.5g.