Abstract
It is important to emphasize that the adjustment of an organic–inorganic interfacial chemical environment plays an important role during the separation performance of composite materials. In this paper, a series of hybrid membranes were prepared by blending polyvinyl alcohol (PVA) solution and sulfonated nano-TiO2 (SNT) suspension. The effects of different interfacial chemical surroundings on ions transfer were explored by regulating the dosage content of SNT. The as-prepared membranes exhibited high thermal and mechanical stability, with initial decomposition temperatures of 220–253 °C, tensile strengths of 31.5–53.4 MPa, and elongations at break of 74.5–146.0%. The membranes possessed moderate water uptake (WR) values of 90.9–101.7% and acceptable alkali resistances (swelling degrees were 187.2–206.5% and weight losses were 10.0–20.8%). The as-prepared membranes were used for the alkali recovery of a NaOH/Na2WO4 system via the diffusion dialysis process successfully. The results showed that the dialysis coefficients of OH− (UOH) were in a range of 0.013–0.022 m/h, and separate factors (S) were in an acceptable range of 22–33. Sulfonic groups in the interfacial regions and –OH in the PVA main chains were both deemed to play corporate roles during the transport of Na+ and OH−.
Highlights
Received: 4 September 2020 Accepted: 18 December 2020 Published: 23 December 2020Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Diffusion dialysis (DD), which is driven by concentration gradient [1], is considered to be one of the most promising methods for alkaline waste water treatment as its spontaneous nature
The alkaline DD process is not used as widely as it has been reported in acid recovery [7,8], which is due to the lower ion coefficients and selectivity
Membranes 1–5% exhibited slightly lower swelling degrees than that of membrane 0%, which indicated that the addition of sulfonated nano-TiO2 (SNT) could restrict the movement of polyvinyl alcohol (PVA) chains
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Different efforts have been made to improve the separation performance of ion exchange membranes. These attempts could be broadly classified into three categories: new membranepreparation methods from monomers that contain many ion exchange groups [5,9,10,11], composite membranes, and organic–inorganic hybrid membranes [12,13,14,15]. Preparation of organic–inorganic hybrid membranes via blending or in situ methods draws the greatest attention because of their multiple functions—unique chemical reac-. HHoowweevveerr,, iitt rreemmaaiinnss cchhaalllleennggiinngg ttoo aaddjjuusstt tthhee cchheemmiiccaall eennvviirroonnmmeennttoof fananinitnertfearcfaecien iancoamcpoomspitoesmiteemmbermanberathnaet cthaantrecganulareteguthlaetteratnhsetproarntsaptioorntaetifofincieefnfcicyieonfciyonosf [io13n,s14[1].3,I1n4o].uIrnporuerviporuesviroeupsorrtep[2o2r–t2[42]2,–i2t 4w],aist cwoansficromnefdirmtheadt tfhuantcftuionncatliognraolugprsoiunposrignaonricg–ainniocr–ginanoircgianntiecrifnacteiarlfarceigailornesgcioonusldcopuroldmportoemtroatnestproarntsopfoirotnosf. iTohnesr.eTfohreer,efsourlefo, snualtfeodnaNteadnoN-TainOo2-T(iSON2T(S)NanTd) apnodlypvoilnyyvlinalycloahlocol h(PoVl (AP)VwAe)rwe ecrheocshenosaesnaans ainnoirngoarngiacnfiilclefrillaenrdanadpoalypmoleyrmmeratmrixattroixptroepparreepharyebhriydbmridemmbermanbersafnoersaflokraalilnkealDinDe iDnDthiins trhesisearrecshe.aTrchhe. eTfhfeectesffoefc–tsSOof3−–SfOro3m− frSoNmT SaNndT–aOnHd –frOomH PfrVoAmoPnVthAeopnertfhoermpaenrfcoermofahnycberiodf hmyebmribdramneems wbrearneedsiwsceurseseddispcureslsiemdinparerilliym. inarily
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