Valorization And Processing Of Industrial Wastewater Via Electrodialysis Using Ion Exchange Membranes

In this thesis,the basic aim and objective were to enhance the process efficiency for the cost-effective and efficient electrodialysis(ED)process and their utilization for ion separation to treat industrial wastewater.Existing membrane-based technologies,such as ED,reverse osmosis(RO),ultrafiltration(UF),and the Donnan dialysis process,have been extensively used by many industries to address overbearing problems in separation processes.Among these processes,ED is convenient for specific industrial applications.The ED process efficiency increases with advanced ED processes such as bipolar membrane electrodialysis(BMED)and selective electrodialysis(SED).Modern techniques are preferable in terms of low energy consumption and high energy efficiency.They are efficient and environmentally friendly because of the production of an acid base in the process that can be further recycled in the mainstream.During acid base production in BMED,different parameters cause issues in the process,significantly affecting process efficiency.Therefore,it is essential to develop new processes in membrane processing for anticipated industrial applications.During the ED,BMED,and SED processes,we used commercial membranes,such as anion membranes(AMX,AMI),cation membranes(CM2),and bipolar membranes(BP-1 E),respectively.In the present work,novel procedures have been acquired to increase the acid base production and resource recovery ratio,which have been explained in the coming chapters.BMED is a promising process for the valorization of salt waste.By taking advantage of the accelerated water splitting in the bipolar membrane(BPM),this technology allows the conversion of the salt(such as NaCl)into the corresponding acid(HCl)and base(NaOH).In most cases,the salinity in the wastewater from various segments and industry sectors was generated by the additional input of acids and bases in the upstream processes.If the salts were transformed into valuable bases and acids,waste salt could be recycled to develop a circular economy with the maximum recovery of valuable components.However,the concentrations of acid and base produced by a typical BMED are not very high,which sometimes restricts the adaptability of the BMED technology.To overcome this low acid base concentration issue,we adopted an advanced BMED processing method that increases the acid base concentration.The 2nd chapter proposed the performance of BMED when treating highly saline wastewater in terms of various operating parameters.The acid and base production efficiency was evaluated;meanwhile,the operating conditions were optimized correspondingly.The wastewater desalination ratio and acid base enrichment were significantly determined by the operating current density and the volume ratio(Vacid:Vbase:Vsait).Using different volume ratios Vacid:Vbase:Vsalt=(1:1:2,1:1:5,1:1:10 and 1:1:15),the recovery of acid and base can be increased to maximum values of 1.3 mol/L and 1.8 mol/L,respectively.The volume ratio Vacid:Vbase:Vsalt=1:1:5 showed low energy consumption of 2.9 kWh/kg and high current efficiency(95.5%).In addition,we tuned to different current densities(30,40,and 50 mA/cm2).The results showed that 50 mA/cm2 is the optimized current density with a high current efficiency of 48.2%and 85.9%for HCl and NaOH and low energy consumption of 2.02 kWh/kg and 3.2 kWh/kg for HCl and NaOH,respectively.Hence,the optimum condition is a current density of 50 mA/cm2 and volume ratio Vacid:Vbase:Vsalt=1:1:5 because of high acid base production,low energy consumption,and high current efficiency compared to others,which was adopted for further investigations.In the 3rd chapter,the main objective was to investigate the feasibility of multistage-batch BMED experiments,including two-stage-batch and three-stage-batch for highly concentrated base generation.We studied the multistage BMED process for base recovery.The multistage process was used for Vacid:Vbase:Vsalt=1:1:2 and Vacid:Vbase:Vsalt=1:1:5 at a current density of 50 mA/cm2;changing the feed and acid has a significant effect on the recovery of the base,without changing the acid compartment in the second stage allowing less base production compared to the change in both the acid and feed solutions.Furthermore,we compared Vacid:Vbase:Vsalt=1:1:2 and Vacid:Vbase;Vsalt=1:1:5 two-and three-stage batch processes for base recovery.The results indicated that the BMED performance of the two-stage batch with Vacid:Vbase:Vsalt=1:1:5 was superior to that of the three-stage batch with Vacid:Vbase:Vsalt=1:1:2.In the 4th chapter,we focused on the effect of different Na-containing inorganic salts(VaF,Na2SO4,NaCl,NaNO3,Na3PO4,Na2CO3)on acid base production.Different anions have different behaviors depending on the size,charge,hydration number,and geometry of ions.The acid base production highly influences its physiochemical properties.The results showed the trend of F->Cl->SO42->NO3->PO43->CO32-by producing high concentrations of HF>HCl>H2SO4>HNO3>H3PO4>H2CO3.The trend was also supported by the acid compartment’s current efficiency and energy consumption.This observation highlights the maj or contribution of ion physiochemical properties to better acid base production.Customizing these intrinsic properties allows high acid production to be obtained and invites further studies to explore the influence of in-depth ionic properties on BMED processing.In the 5th chapter,we studied the treatment of lithium and sodium containing organic matter wastewater using BMED,working on the idea of the separation of monovalentmonovalent ions.We synthesized a negatively charged complex solution of sodium acetylacetonate Na(AcAc)by reacting lithium and sodium ions with acetylacetonate.The results confirmed that the migration of sodium ions toward the acid compartment reached 0.03,0.04 and 0.068 mol/L during different concentration and current density experiments,demonstrating the successful separation of Na+ions from Li+ions by producing a negative complex of sodium acetylacetonate Na(AcAc).In contrast,the Li+ ion concentration(0.00120.0013 and 0.0014 mol/L)in the acid compartment was almost negligible.These results support our proposed mechanism of monovalent-monovalent ion separation.In the 6th chapter,we compared the nanofiltration(NF)and SED techniques for acid recovery from molybdenum industrial wastewater and integrated these techniques to enhance acid recovery.The optimization of constant voltage in SED and pressure in NF were performed in the first step.The best constant voltage was declared as 6 V,and the better pressure effect was 1 MPa.The maximum acid recovery of 89.6%was obtained in SED,making it superior to NF,where the acid recovery was not much higher(59.1%).These optimized conditions were further employed in the NF-SED coupled system.The integrated system further increases the acid recovery,and approximately 94.2%of acid can be recovered.Furthermore,post-treatment was carried out for MoO3 nanoparticle recovery.