Construction Of Superhydrophobic Surface Of Melamine Sponge And Its Emulsion Separation Performanc

The pollution of oily wastewater has become a major global challenge.Designing efficient oil-water separation materials for the effective treatment of oily wastewater has received widespread attention.The monolithic oil-water separation materials,which are designed based on the modification of melamine sponge(MS),have become a novel material with great potential for oily wastewater treatment.However,there are still some deficiencies in the modification methods for MS,such as complex,costly,poisonous,unstable and so on.The prepared oil-water separation material still has defects,such as being difficult to apply to complex and harsh environments,and difficult to effectively separate emulsions.These have greatly limited its application in the actual oily wastewater treatment.Therefore,developing a facile,efficient,low-cost,and environmentally friendly modification method has become the key to current research.This thesis focuses on regulating the surface properties of MS.A series of modification methods are used to change the surface properties of the sponge,such as surface wettability,surface roughness,surface chemical energy,and surface charge.And the prepared monolithic oil-water separation material based on MS can be effectively applied to oily wastewater including layered oil-water mixtures and emulsions.The main contents include the following three aspects:Firstly,in this thesis,the modification method based on the in-situ chemical reaction of MS surface was explored.It was found that chemical reagents including potassium persulfate,ammonium persulfate,hydrogen peroxide,nitric acid,can chemically modify MS and change its surface hydrophilicity and hydrophobicity.Further,the mechanism of nitric acid changing the surface properties of MS was mainly explored.The research results show that this one-step synergistic superhydrophobic modification method based on nitric acid can prepare a novel monolithic oil-water separation material(HMMS),which has superhydrophobicsuperoleophilic properties,and is suitable for the separation of layered oil-water mixtures.Meanwhile,it has been found that it has good adsorption capacity,selective separation ability,recycling ability,and can be applied in different harsh environments.However,the oil-water separation material prepared by this modification method cannot be applied to the separation of emulsions.In order to design a monolithic oil-water separation material with the function of separating emulsion,a method based on coating modification was introduced.In this study,magnesium hydroxide(MH)nanoparticles with different types of charges were adhered to the surface of MS,respectively.Subsequently,stearic acid is further dip-coated.These regulate the surface properties of MS,including surface charge,surface roughness,surface chemical energy,hydrophilicity and hydrophobicity,etc.The monolithic oil-water separation material(SMH/MS)prepared in this way can not only effectively separate layered oil-water mixtures,but also specifically separate emulsions containing anionic or cationic surfactants.In further investigation of its application ability in the treatment of actual oily wastewater,it was found that this novel monolithic oil-water separation material also has excellent performance in terms of mechanical properties,recycling performance,continuous separation performance,etc.The coating method usually requires a binder to combine the modified material and the substrate,and need to design superhydrophobic surface step by step.And the prepared materials are difficult to apply in a complex and harsh environment.In order to solve the above problems,a coating modification method based on MA-LDH in-situ growth was designed,and a novel oil-water separation material(MA-LDH/MS)was successfully prepared.In this work,the effect of this coordinated modification method based on MS and modified coatings on the surface properties and overall performance of the obtained oil-water separation material was systematically explored and analyzed.It was found that the effective combination of MA-LDH and MS does not need the binder,and can be superhydrophobic modified in one step.Meanwhile,this oil-water separation material can be effectively used to separate layered oilwater mixtures and cationic surfactant-stabilized emulsions.And it has good applicability in different environments and has potential application value.