Synergistic and nonsynergistic surfactant-water mixtures of sodium dodecyl sulfate (SDS), lauryl betaine (C12B), and cocoamidopropyl betaine (CAPB) systems are studied using molecular simulation to understand the role of interactions among headgroups, tailgroups, and water on structural and thermodynamic properties at the air-water interface. SDS is an anionic surfactant, while C12B and CAPB are zwitterionic; CAPB differs from C12B by an amide group in the tail. While the lowest surface tensions at high surface concentrations in the SDS-C12B synergistic system could not be reproduced by simulation, estimated partitioning between surface and bulk shows trends consistent with synergism. Structural analysis shows the influence of the SDS headgroup pulling C12B to the surface, resulting in closely packed structures compared to their respective homomolecular-surfactant systems. The SDS-CAPB system, on the other hand, is nonsynergistic when the surfactants are mixed on account of the tilted structure of the CAPB tail. The translational excess entropy due to the tailgroup interactions discriminates between the synergistic and nonsynergistic systems. The implications of such interactions on surfactant effects in complex, multicomponent atmospheric aerosols are discussed.

During electrochemical machining (ECM) of metals, the electrolyte gets polluted by heavy metal ions and compounds. This creates crucial process control problems due to variation in electrical conductivity and is an environmental threat if the solution is discharged without treatment. In this study, an economical, simple multistep treatment system based on ion-exchange was developed to remove metal ions from the polluted electrolyte. We specifically looked at the electrolytic discharge from ECM of copper pieces, which is widely used in biomedical and electronic applications. Three different ion-exchange media were used: (1) a natural zeolite, (2) a special type of adsorbent quantitative filter paper, and (3) a polymer-based synthetic cation-holder resin (Lewatit TP 207) that works well with copper ions. Optimization studies for pH and contact time showed the following: (1) by using zeolite alone, and after 2 h of mixing, 43.2% of Cu2+ could be removed; (2) by using the filter paper alone, and after three times of filtration, 90% of Cu2+ could be removed; and (3) by using Lewatit TP 207 alone, 100% of Cu2+ could be removed. While Lewatit TP 207 allowed for 100% removal of Cu2+, its use alone is costly and troublesome due to constraints from service life and multistep regeneration and conditioning with strong acids and bases, respectively. The most simple and economical scheme for removal of Cu2+ and recycling the electrolyte for reuse was the three-step zeolite-filter-resin treatment system.

ÖZETYeni bir elektrokimyasal işleme tezgahında bakır iş parçalarının işlenmesi sonrası ağır metal iyonları ile kirlenen elektrolitin sisteme yeniden beslenmeye hazır hale getirilmesi amacı ile tezgah çevre birimleri dahilinde arıtım yöntemleri incelenmiştir. Elektrokimyasal işleme (EKİ), metal bir parçanın yüzeyinin iyonlaştırma yöntemi ile işlenmesine ve metal iyonlarının elektrolit ile işleme bölgesinden uzaklaştırılmasına dayanmaktadır. Endüstriyel sularda bulunan ağır metal iyonlarının giderilmesi ve suların yeniden kullanıma hazır hale getirilmesi sistem verimliliğinin arttırılması ve çevre sağlığının korunması açısından önem taşımaktadır. Bu çalışmada, EKİ sonucu bakır iyonları ile kirlenen elektrolitin arıtılması için iyon değiştirme yöntemi tercih edilerek üç-aşamalı bir uygulama önerilmiştir. İyon değiştirici olarak birinci aşamada kağıt filtre, ikinci aşamada Türkiye'de yaygın rezervleri bulunan doğal bir zeolit ve son aşamada polimer bazlı katyon tutucu Lewatit TP 207 reçinesi kullanılmıştır. Bakır iyonları ile kirlenen elektrolitte zeolit ile iki saat etkileşim sonucu % 40, kağıt filtre ile üç kez filtreleme sonucu % 90, Lewatit TP 207 reçine kolonu ile işlem sonrası ise % 100 oranında arıtma sağlanmıştır.Anahtar Kelimeler: Ağır metal iyonu, İyon değiştirme, Metal işleme, Elektrokimyasal işleme DETERMINATION AND REMOVAL OF COPPER IONS (CU 2+ ) IN THE WASTE ELECTROLYTE IN AN ELECTROCHEMICAL MACHINING APPLICATION ABSTRACTWater treatment methods, as part of the peripheral units of a novel electrochemical machining device, were investigated with the aim of preparing the electrolyte, which was contaminated with heavy metal ions after machining of copper work pieces, for refeeding back to the system. Electrochemical machining (ECM) depends on machining the surface of a metal piece by ionization and removal of metal ions from the work area via the electrolyte. Removal of heavy metal ions in industrial waters and treatment of these waters for reuse is crucial in terms of increasing system efficiency and protecting environmental health. In this study, the ion exchange method was selected and a three-step application is proposed for the treatment of the electrolyte contaminated with copper ions after ECM. As the ion-exchanger, a paper filter was used in the first step, a natural zeolite with wide reserves in Turkey was used in the second step, and a polymer based cation exchange Lewatit TP 207 resin was used in the final step. Purification of the electrolyte, contaminated with copper ions, was achieved at 40 % as a result of treatment with the zeolite for two hours, at 90 % as a result of filtering three times using the paper filters, and at 100 % after treatment with the Lewatit TP 207 resin.