| Material synthesis,novel ion exchange membrane preparation,and their applications are the basic needs for emerging processes such as wastewater treatment,alkaline fuel cell,and gas separation.Novel anion exchange membranes were prepared from various polymers architecture and functional groups.The selection of polymers is based on the membrane applications.Particularly,this thesis focuses on the preparation of novel anion exchange membranes for potential application in diffusion dialysis,electrodialysis,and anion exchange membrane fuel cell(AEMFC).The performance of fabricated membranes was judged with the help of various properties,operating parameters,and conditions,as well as compared with the commercial membranes for the potential application in their respective fields.The electrochemical and physical properties of fabricated membranes including ion exchange capacity,water uptake,chemical stability,linear expansion ratio,thermal stability,alkaline stability,and mechanical stability were tested and evaluated.The lumped process parameter model,multivalent complexation effects and the influence of significant operating parameters on the diffusion dialysis process were widely explored.The effect of hydrophobicity on the membrane perm-selectivity for the Cl-/SO42-system was investigated in electrodialysis.Moreover,the alkaline stability,methanol permeability and selectivity were examined for the anion exchange membranes(AEMs)to be potentially applied in the anion exchange membrane fuel cell.In this thesis,novel anion exchange membranes(QUDAP AEMs)were designed,fabricated and employed for the acid recovery by diffusion dialysis.The morphological and thermo-mechanical properties of the prepared AEMs were examined by the scanning electron microscopy(SEM),dynamic mechanical analysis(DMA),thermogravimetric analysis(TGA),and Fourier transform infrared spectroscopy(FTIR).The developed AEMs have good proton dialysis coefficients and separation factors compared to commercial membrane DF-120.Moreover,a lumped process parameter model was designed and developed to examine the diffusion coefficient and molar flux of acid across the membrane,as well as variation in feed volume during the acid recovery by diffusion dialysis process.The model predictions and experimental results were compared,while the predictions consequences suggested that the developed model can provide a reasonable agreement with the experimental outcomes.The spent pickling agent contains zinc,iron,aluminum,and sodium,as well as the salts of these metals.These metals and their salts are directly affecting the membrane performance in term of acid recovery.Therefore,a series of novel AEMs consist of polyvinyl alcohol(PVA)and a different quantity of synthesized anion exchange precursors were effectively fabricated and used for acid recovery via diffusion dialysis(DD).The acid dialysis coefficients(UH)were ranged from 0.0194 to 0.0295 m/h and the separation factors were in the range of 27.84 to 52.60 at 25 ? for FeCl2-HCl system.Furthermore,a good performance membrane(Q-DAN-4 AEM)was chosen to investigate the effect of metal species in a waste solution including Zn2+,Fe2+,Al3+,and Na+on acid dialysis coefficient and membrane selectivity.The experimental results suggested that the existence of different metal salts in HCl solution is influencing the acid diffusivity and membrane selectivity during the DD process because of complexation of metal ions and acid.These observations showed that this work provides a significant clue for the further study to investigate the effect of multivalent complexation on acid recovery during commercial applications.To examine the effect of process parameters is an important step for the improvement of diffusion dialysis to recover the acid during industrial application.A fabricated AEM membrane(MDMH-QPPO-5)was chosen based on the performance and chemical stability to mathematically and statistically investigate the influence of process parameters on the DD process.The full factorial design(FFD)was used to analyze the effect of process parameters including feed concentration,time and temperature on acid recovery during diffusion dialysis.The half-normal plot showed the order of significant process parameters that considerably influencing the acid recovery and membrane selectivity.The experimental observations investigated that the evaluating of significant process parameters is very necessary to enhance the acid recovery by DD process.The saline wastewaters are continuously produced in numerous industries such as pharmaceutical,paper mills,tannery,and petroleum.The high concentrations of chlorides and sulfates in these wastewaters are directly discharged to the environment and seriously affecting the surface water,soil,groundwater,and aquatic life.Considering this issue,electrodialysis is an efficient and green technology to reduce the harmful wastes and achieve salt resource through recycling.AEMs with high monovalent divalent separation capability is the core component of electrodialysis to treat these saline wastewaters.To get the desired goal,AEMs with alkyl spacers were prepared by an effective and facile method.The cationic alkyl spacers including QPP,QHP,and QUP were synthesized and confirmed by proton nuclear magnetic resonance(NMR).The prepared AEMs showed high perm-selectivity for Cl-/SO42-system and compared with commercial monovalent selective ACS membrane.It has been observed that the perm-selectivity of Cl-/SO42-mixture was enhanced with the enhancement in chain length of alkyl spacer and membrane hydrophobicity.The fabricated AEMs show long term stability for industrial application.The idea established here is flexible and may be utilized to prepare AEMs from various functional groups and polymeric backbones.AEM is more attractive to enhance the fuel cell performance while it makes more sustainable,effective and practical commercialization of AEMFC.It is a core component of alkaline polyelectrolyte fuel cells.However,high hydroxide conductivity,suitable alkaline stability,and excellent mechanical stability are still challenging issues for the researchers.Therefore,N-methyl dipicolylamine(MDPA)was designed and synthesized,while it acts as an amazing structure that resists against alkali attack.MDPA-AEMs were prepared and evaluated for their alkaline stability,hydroxide conductivity,methanol selectivity and methanol permeability for their prospective application in AEMFC.The results showed that MDPA-AEMs possessed excellent alkaline stability,reasonable water uptake,low methanol permeability,low swelling ratio,high selectivity,and high hydroxide conductivity despite high IEC values.In addition,the fabricated AEMs have outstanding mechanical stability with Eb values of 13.21 to 32.48%and TS values 36.86-67.57 MPa.The.designed and synthesized cationic head group(MDPA)was more alkaline stable and highly-OH conducting agent,while it may be a prospective candidate for the fabrication of high hydroxide conducting AEMs.The developed approach for AEMs preparation is acknowledged as a feasible path toward the high hydroxide conduction in the alkaline environment at a higher temperature. |
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