Novel Thermosensitive-co-Zwitterionic Sulfobetaine Gels for Metal Ion Removal: Synthesis and Characterization.

Zwitterionic betaine polymers are promising adsorbents for the removal of heavy metal ions from industrial effluents. Although the presence of both negative and positively charged groups imparts them the ability to simultaneously remove cations and anions, intra- and/or inter-chain interactions can significantly reduce their adsorption efficiencies. Therefore, in this study, novel gels based on crosslinked co-polymers of thermosensitive N-isopropylacrylamide (NIPAAM) and zwitterionic sulfobetaine N,N-dimethylacrylamido propyl ammonium propane sulfonate (DMAAPS) were synthesized, characterized, and evaluated for ion removal. Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) analyses confirmed the success of the co-polymerization of NIPAAM and DMAAPS to form poly(NIPAAM-co-DMAAPS). The phase transition temperature of the co-polymer increased with increasing DMAAPS content in the co-polymer, indicating temperature-dependent amphiphilic behavior, as evidenced by contact angle measurements. The ion adsorption analyses of the poly(NIPAAM-co-DMAAPS) gels indicated that co-polymerization increased the molecular distance and weakened the interaction between the DMAAPS-charged groups (SO3- and N+), thereby increasing the ion adsorption. The results confirmed that, with a low concentration of DMAAPS in the co-polymer gels (~10%), the maximum amount of Cr3+ ions adsorbed onto the gel was ~58.49% of the sulfonate content in the gel.

Validation of measured microwave absorption and temperature change for development of a single-mode-type microwave heating thermogravimetry apparatus.

The temperature distribution, microwave absorption efficiency, and dielectric properties of a copper (ii) oxide (CuO) pellet heated by microwave irradiation were investigated for use in developing a single-mode-type microwave heating thermogravimetry apparatus. The validity of the apparatus was confirmed by comparing the measured data with the results of numerical simulations. The dielectric properties and error margins of other parameters estimated using the apparatus were also examined. The temperature distribution of the CuO pellet was observed to decrease monotonously on moving from the outlet to the inlet side of the apparatus. A three-dimensional numerical simulation of the electromagnetic field accurately reproduced this temperature distribution, suggesting the one-way movement of microwaves in the single-mode-type microwave apparatus. The numerically determined dependency of the CuO absorption efficiency was also found to be in very good agreement with published data. The same was the case with the permittivity loss of the CuO at various temperatures, as estimated from the measured microwave absorption efficiency. However, a larger error was observed in the estimation of the permittivity loss of a material with a lower microwave absorption efficiency, which was apparently due to the measurement error of the absorption efficiency of such a material.