Construction Of Hollow Zirconia And ZIF-8@s-EPS And Their Applications In Water Treatment

With the rapid increase of population,many problems have emerged.Among them,water pollution and water shortage are the two major issues that need to be addressed urgently.Due to the intensification of people’s life and production activities,the discharge of wastewater has also increased,and the freshwater development has become more difficult.In fact,wastewater contains harmful substances in quantity,such as heavy metals,pesticides,fertilizers,etc.These pollutants could cause damage to fresh water extraction equipment,such as rust,scaling,etc.In order to solve these problems,adsorption method is commonly used to remove harmful substances in sewage treatment.At present,porous materials are widely used as adsorbents because of their characteristics of large specific surface area,high efficiency and environmental protection.However,the function of porous adsorbent is relatively simple,so the development of multifunctional materials will become the trend.In the study,two kinds of multifunctional biometallic materials are synthesized based on good biocompatibility.One is to synthesize zirconia with hollow mesoporous structure（hm-ZrO₂）by hard template method.The other is to synthesize a novel material with biological multifunctional properties,namely ZIF-8@s-EPS.It is prepared by ZIF-8 and Bacillus megaterium soluble extracellular polysaccharide（s-EPS）.The main research contents are as follows:（1）The specific surface area of hm-ZrO₂ was 184.311 m~2/g by BET method.Thus,hm-ZrO₂ could effectively adsorb Pb²⁺,Ni²⁺and malathion.The adsorption efficiency of Pb²⁺,Ni²⁺and malathion was the highest when the concentration of hm-ZrO₂ was 0.666g/L,1 g/L and 0.333 g/L,respectively.And the optimized p H was 4 and 6 for Pb²⁺and Ni²⁺.The adsorption of malathion,Pb²⁺and Ni²⁺all followed the quasi-second-order equation through the exploration of time.The adsorption process of malathion,Pb²⁺and Ni²⁺by hm-ZrO₂ was spontaneous and endothermic through the exploration of temperature.Through the study of initial concentration of adsorbate,the results indicated that Pb²⁺adsorbed by hm-ZrO₂ followed Freundlich model.And the n value was 2.221,indicating that the adsorption process of Pb²⁺by hm-ZrO₂ was easy to occur.The adsorption of Ni²⁺followed Langmuir model,and the Q_m of Pb²⁺was 51.55 mg/g,which was close to the experimental value of 45.73 mg/g.The adsorption of malathion by hm-ZrO₂ also conformed to Langmuir model,and the Q_m was 54.11 mg/g.According to the above results,the adsorption of malathion,Pb²⁺and Ni²⁺by hm-ZrO₂ was mainly chemisorption.This was the first time that hm-ZrO₂ had been used as a bifunctional adsorbent in water treatment.The adsorbent was expected to adsorb and remove other wastes in wastewater.（2）s-EPS rich in carboxyl,amino and amide groups was used to functionalize ZIF-8 in this paper.XPS characterization confirmed that these active functional groups were adsorption sites for Ca²⁺and inhibited the binding of Ca²⁺with HCO₃^-and SO₄^2-,so as to achieve the effect of scale inhibition.The response surface method was used to study interaction effects of the scale inhibitor dosage,time and temperature.The experimental results showed that the scale inhibition efficiency of ZIF-8@s-EPS on Ca CO₃ and Ca SO₄could reach 98.63%and 99.40%under the conditions of 3 m L of scale inhibitor,15 h and20℃.In addition,it was observed that ZIF-8@s-EPS could inhibit the adhesion of Pseudomonas aeruginosa and its biofilm on stainless steel by fluorescence microscopy and confocal laser microscopy.It was due to the release of Zn²⁺from ZIF-8@s-EPS,and the functional groups also had antibacterial activity.Thus,ZIF-8@s-EPS had a good antibacterial activity,and the antibacterial rate was about 89.4%.It was found that ZIF-8@s-EPS was hydrophilic through the water contact angle test,which could protect the stainless steel from the adhesion of protein.The multi-functional biometallic material was first applied to scale inhibition,antibacterial and antifouling.Therefore,the functionalization of s-EPS to metal materials with hydrophilic properties will be expected to become a novel way to develop multi-functional biomaterials.