Study On The Mechanism And Method Of Saline Wastewater Treatment Via Phase Change Sorption Using Ionogel And Hydrate

Against the background that global sustainable development faces three major problems—population,energy,and environment,water resource scarcity and water environment deterioration have become global problems.How to solve the contradiction between socio-economic development and the supply and demand of water resources,and realize the coordinated development of water resources,society,economy,and ecological environment,is an important issue that needs to be solved urgently.At present,wastewater treatment and reuse is widely regarded as an important means to solve the water crisis.However,the traditional water treatment methods have many shortcomings such as complicated process,secondary pollution,high energy consumption and poor universality.Therefore,the core objective of this research is to explore novel,safe,economical and efficient universal water treatment methods to solve the above problems.This study proposes saline wastewater treatment using ionogel and hydrate,optimizes the preparation method and formulation to make ionogels have good performance,and then analyzes their potential of saline wastewater treatment.On the other hand,the study builds a theoretical basis for saline wastewater treatment using hydrate formation,analyzes the effects of the pollutant concentration and types,and the dosage of hydrate former on ion removal characteristics,illustrates the controlling factor and limiting factor of removal efficiency,and finally carries out techno-economic analysis of both methods.The characteristics of ionogel are the most important factors to determine the treatment performance of saline wastewater by ionogel adsorption.To solve this problem,PEGDA-based and silica-based EMIM Ac ionogels are synthesized.The applicability of UV polymerization,microwave polymerization,and thermal polymerization to the preparation of PEGDA-based ionogels is compared.The results showed that multichannel 60.07 wt.%PEGDA-based ionogel with good hydrothermal stability,chemical stability and surface morphology can be synthesized via thermal polymerization at 60? within 30 min.The water uptake of the ionogel is 5.15 times for silica gel and 3.75 times for activated carbon at 90.00%RH.Silica-based EMIM Ac ionogels are synthesized using Syloid 63FP and 72FP as solid matrix via incipient wetness impregnation.It is found that Syloid 63FP-based ionogel can have a maximum ionic liquid content of 49.69 wt.%at low humidity(40%RH)while ionic liquid leakage and ionogel fragmentation can be found at high humidity(80%RH).The maximum ionic liquid contents of Syloid 72FP-based ionogel at low and high humidity are 59.98 wt.%and 49.86 wt.%,respectively.Moreover,50.14 wt.%Syloid 72FP-based ionogel has good hydrothermal stability,chemical stability,and surface morphology.The water uptake of the ionogel is 5.89 times for silica gel and 4.29 times for activated carbon at 90.00%RH.Finally,50 wt.%Syloid 72FP-based EMIM Ac ionogel is used to carry out studies on the treatment of saline wastewater via ionogel adsorption,the result shows the specific daily water production can be up to 24.9 kg/(kg*d).By selecting hydrate former with a greater driving force(atmospheric pressure,8.4?),saline wastewater treatment via hydrate formation using R141b as hydrate former is studied.It is found that the electrical conductivity of residual solution increases during hydrate formation,and the characteristic peaks of ions are not found in Raman spectra of hydrate,the ion concentrations in the dissociated water are close to zero,and all these confirm the non-guest exclusion of hydrate.The concentration gradient theory of boundary layer near hydrate formation front is put forward,the results reveal that the ion concentration at the boundary layer increases but the relative deviation decreases with the increase of the initial concentration.It is found that the removal efficiency was higher when the pollutant concentration is higher and the dosage of hydrate former is smaller,but the water yield and enrichment factor are smaller.Through the observation of hydrate microstructure,the composition proportion and occurrence rule of hydrate slurry before and after the solid and liquid separation are analyzed.Five solid-liquid separation methods are used to reduce the trapped solution and improve the removal efficiency.It is found that the combination of vacuum filtration(1 min)and centrifugation(1580 N and 9 min)can achieve the removal efficiency of 96.63%.The study also proposes a suitable economic analysis model for saline wastewater treatment using ionogel and hydrate,designs the corresponding technological processes.The unit production costs of both methods are calculated considering the initial capital cost,interest rate,maintenance and operation cost(electricity charges,chemical reagents,labor).The results indicate that the unit production cost of ionogel adsorption method is higher than that of hydrate method.By utilizing free low grade heat driven heat pump for cooling and heating,the unit production costs of saline wastewater treatment using ionogel and hydrate can be further reduced.Through technical analysis and comparison,it is believed that the ionogel method has higher water quality,and the hydrate method has wider applicability and lower energy consumption.In conclusion,saline wastewater treatment using ionogel and hydrate can realize the economical and efficient treatment of saline wastewater,which has a good application prospect and is of great significance for solving the global water shortage and water environment deterioration.