Study Of Phosphorus Adsorption From Malodorous Black Water And Slow-releasing Characteristic From Modified Hydrotalcite Materials

Driven by the eutrophication of the water body and global"phosphorus crisis",the phosphorus removal and recovery from phosphorus-rich water bodies have become a hotspot in the water research field.The treatment of malodorous black water faced a serious challenge of high phosphorus content,therefore the removal and recycle of phosphorus from the malodorous black water not only guaranteeing the long-term effect of water environmental treatment,but also realizing the recycle of phosphorus resources in sewage.This work selected urban malodorous black water as research object,to investigate typical malodorous black water in Jiangsu province,and has analyzed the water quality characteristics of malodorous black water.Based on the characteristics of high phosphorus and dissolved organic matter content in the malodorous black water,this work carried out the experiment of phosphorus adsorption by using modified hydrotalcite in the simulated solutions.We aimed to explore the phosphorus adsorption kinetics to modified hydrotalcite in solutions with different phosphorus contents and p H values.Besides,this study also clarified the interaction mechanism between dissolved organic matter and phosphorus adsorption processes to modified hydrotalcite.Based on the nutrient slow-releasing experiment,the nutrient releasing behavior form phosphorus-rich hydrotalcite was analyzed,and the results could be used to evaluate the stability and phosphorus utilization potential of phosphorus-rich hydrotalcite.The main conclusions are as follows:（1）The investigated typical malodorous black water bodies in Jiangsu province showed that high phosphorus content level,which ranging from 0.14 mg/L to 3.09 mg/L.The Mg-Al hydrotalcite modified by calcining at 300℃has excellent adsorption properties to phosphorus in solutions with different p H values and initial phosphorus concentrations and malodorous black water.The results showed that in the p H range of6.5～8.0,the adsorbed quantity of phosphorus has less affected by the p H value.When the phosphorus initial concentration increases from 2.10 mg/L to 22.00 mg/L,the adsorbed quantity of phosphorus onto adsorbent also increased,and the phosphate extraction quantity increased from 2.04 mg/g to 21.96 mg/g,meanwhile the phosphorus removal rate reached 94.4%in the malodorous black water sample.（2）Humic acids（HA）which is an important component of dissolved organic matters in malodorous black water would affect the phosphorus adsorption process of modified hydrotalcite by competitive adsorption.The research of kinetic showed that kinetic data of phosphorus and humic acid adsorption by the modified hydrotalcite fitted well with the quasi-second-order kinetic equations.According to the fitting results,in the HA concentration range of 0 mg/L to 150.0 mg/L,the adsorbed quantity of phosphorus has a limited influence with the increase of humic acid concentration,and the phosphorus adsorption amount maintained in the range of 9.8 mg/g to 9.2 mg/g.In addition,in the phosphorus concentration range of 0 mg/L to 150.0 mg/L,the adsorbed quantity of humic acid decreased with the increase of phosphorus concentration,which decreased from 87.6 mg/g to 55.6 mg/g.The comparison of phosphate and HA adsorption behavior to LDH adsorbent showed that phosphate anions had advantage in the ion exchange process.（3）The modified hydrotalcite has a good stability in the process of slow release,and slow release behavior of modified hydrotalcite indicated that the modified hydrotalcite has a slow release effect on phosphorus.The sustained release experiments showed that after 365 hours,sustained release rate of phosphorus in Na HCO₃ solution and deionized water were 14.5%and 7.3%,respectively,and that of humic acid in Na HCO₃ solution and deionized water separately were 4.5%and 3.6%.It indicated the sustained release levels of phosphorus and humic acid in Na HCO₃ solution were higher than that in deionized water,furthermore modified hydrotalcite has a better sustained-release rate to phosphorus than humic acid organic matte and it has the potential to be a sustained release phosphate fertilizer.