植酸改性提高污泥基水热炭的镉吸附固定性能

Phytic Acid Modification Enhanced Cadmium Sorption and Immobilization of Sludgebased Hydrochar

在污泥水热炭化过程中添加植酸,采用一步共水热法制备得到植酸改性水热炭(PHC),在对其表面形貌、孔隙结构、元素组成、官能团和热稳定性进行表征的基础上,系统比较了镉(Cd)在未改性水热炭(HC)和PHC上的吸附行为,并考察了腐植酸、温度和pH对吸附过程的影响,最后通过土壤钝化试验评估了PHC对土壤中Cd的固定能力.结果表明,PHC表面富含磷酸基团,电负性和热稳定性增强,具有较低的重金属浸出风险,对Cd的吸附速率和最大吸附容量分别是HC的1.88倍和1.22倍,这归因于磷酸基团的引入增强了对Cd的络合作用和静电作用;升温、pH值增加和腐植酸共存都有利于Cd在PHC上的吸附;在其他重金属共存(Cu、Zn和Pb)时,PHC表现出较强的选择性,对Cd的吸附容量高于其他金属0.77~6.88倍.PHC还具有良好的土壤Cd固定效率(56.1%~81.1%),且缓解了土壤速效养分的流失,显著增加了土壤有效磷含量.总之,植酸改性的污泥基水热炭可以有效去除水体Cd,同时也可作为土壤改良剂,有效稳定土壤Cd含量,是一种具有应用前景的污泥资源化途径.

Phytic acid-assisted sludge hydrothermal carbonization was employed to synthesize phytic acid-modified hydrochar via a one-step method.The surface morphology,pore structure,elemental composition,functional groups,and thermal stability of the phytic acid-modified hydrochar were characterized.Sorption kinetics and isotherm experiments were conducted to investigate the effects of humic acid,temperature,and pH on the sorption process of cadmium(Cd)onto the phytic acid-modified hydrochar.The Cd fixation ability was evaluated through soil passivation experiments.The results demonstrated that the surface of the phytic acid-modified hydrochar exhibited an abundance of phosphoric acid groups,enhanced electronegativity,and thermal stability.Furthermore,both the sorption rate and maximum sorption capacity for Cd increased by 1.88 times and 1.22 times compared to that in unmodified hydrochar,respectively,owing to the presence of phosphoric acid groups that enhanced complexation and electrostatic interaction with Cd.Elevated temperatures,higher pH values,and coexistence with humic acids were beneficial for enhancing Cd sorption onto phytic acid-modified hydrochar.When heavy metals such as Cu,Zn,and Pb coexisted,the sorption capacity of phytic acid-modified hydrochar for Cd was 0.77-6.88 times higher than that for other metals.Phyic acid-modified hydrochar exhibited excellent efficiency in fixing Cd(56.1%-81.l%),mitigating the loss of available nutrients in soil and significantly increasing the AP content in the soil.In conclusion,the use of phytic acidmodified hydrochar could effectively remove Cd from water and serve as a promising soil amendment for stabilizing soil Cd content.