改性生物炭制备条件对磷吸附性能的影响

Effect of Preparation Conditions on the Phosphorus Adsorption Capacitiesof Modified Biochar

为获得高性能磷吸附材料,实现污染水体磷元素的高效回收利用,以食用菌菌渣为原料,研究改性条件对生物炭磷吸附性能的影响,分别为:KOH改性生物炭(BCK)、镁改性生物炭(BCM)、钙改性生物炭(BCC)、钙镁改性生物炭(BC/CM)及鸡蛋壳改性生物炭(EC)。实验对比发现:(1)热解温度是影响磷吸附效果的重要因素,不同温度制备的生物炭吸附性能差异较大。在600—900℃温度下制备的生物炭中,800℃条件下制备的生物炭吸附性能最佳,这是因为较高的温度有利于生物炭孔隙率的提高,但温度过高时亦会导致生物炭孔隙结构的坍塌;(2)鸡蛋壳与菌渣直接混合制备的生物炭一步实现扩孔与金属氧化物负载,磷吸附能力高于另外3组处理组,去除效果最佳,钙镁双金属浸渍改性生物炭对磷的吸附效果显著优于镁改性及KOH改性,4种改性生物炭的磷吸附能力由高到低依次为EC>BC/CM>BCC>BCM>BCK;(3)在蛋壳与生物炭的比例小于2꞉1时,改性生物炭的磷吸附能力随蛋壳添加量的增加而增大。然而,进一步增加蛋壳的添加量会导致碳含量的降低,且CaO在生物炭表面的沉积会破坏生物炭的多孔结构,降低其对磷的吸附能力。此外,实验还发现以蛋壳与生物炭比例为1꞉1制备的生物炭对磷的吸附能力最高,可达159.69 mg·g−1,是未改性生物炭的5倍。这些结果表明,蛋壳改性生物炭在废水中磷的回收利用方面具有很大的潜力。

To obtain high-performance phosphorus adsorption materials and realize efficient recovery and utilization of phosphorus in waste water,the effects of modification conditions on the phosphorus adsorption properties were studied for modified biochar based on mushroom residue,including KOH modified biochar(BCK),egg shell modified biochar(EC),magnesium modified biochar(BCM),calcium modified biochar(BCC)and calcium magnesium modified biochar(BC/CM).The experimental results show that:(1)Pyrolysis temperature is an important factor influencing the phosphorus adsorption capacity of biochar.Among the biochar those are prepared at 600–900℃,higher temperature is beneficial to the improvement of biochar porosity,but too high temperature leads to the collapse of pore structure of the biochar.It is determined that biochar prepared at 800℃has the best adsorption performance;(2)The biochar prepared by the direct mixing egg shell and mushroom residue could simultaneously load metal oxide and further increase the biochar porosity,thus their phosphorus adsorption capacity is higher than the biochar prepared by other methods.In addition,the phosphorus adsorption efficiency of biochar co-modified with CaO and MgO was obviously higher than those of magnesium or KOH modified biochar.The order of phosphorus adsorption capacity from high to low is EC>BC/CM>BCC>BCM>BCK;And(3)within the ratio of eggshell to biochar lower than 2꞉1,the phosphorus adsorption capacity of the modified biochar increases with the increase of the addition amount of eggshell.However,further increase the amount of eggshell would bring to the decreases of the carbon content in the mixture,and the deposition of CaO on the surface of the biochar would destroy the porous structure of the biochar,lowering the phosphorus adsorption capacity.Furthermore,it is found that of the biochar prepared with the eggshell to biochar ratio of 1꞉1 has the highest phosphorus adsorption capacity,which can reach 159.69 mg·g−1 and is 5 times more than that of biochar without modification.These results show great potential of the egg shell modified biochar in recycling of phosphorus in waste water.