Mohammad Mizanur Rahman Khan

Synthesis of Potato Starch-Acrylic-Acid Hydrogels by Gamma Radiation and Their Application in Dye Adsorption

Several kinds of acrylic-acid-grafted-starch (starch/AAc) hydrogels were prepared at room temperature (27°C) by applying 5, 10, 15, 20, and 25 kGy of gamma radiation to 15% AAc aqueous solutions containing 5, 7.5, and 15% of starch. With increment of the radiation dose, gel fraction became higher and attained the maximum (96.5%) at 15 kGy, above which the fraction got lowered. On the other hand, the gel fraction monotonically increased with the starch content. Swelling ratios were lower for the starch/AAc hydrogels prepared with higher gamma-ray doses and so with larger starch contents. Significant promotions of the swelling ratios were demonstrated by hydrolysis with NaOH: for 15 kGy radiation-dosed [5% starch/15% AAc] hydrogel, while the maximum swelling ratio was ~200% for those without the treatment. The authors further investigated the availability of the starch/AAc hydrogel as an adsorbent recovering dye waste from the industrial effluents by adopting methylene blue as a model material; the hydrogels showed high dye-capturing coefficients which increase with the starch ratio. The optimum dye adsorption was found to be 576 mg per g of the hydrogel having 7.5 starch and 15% AAc composition. Two kinetic models, (i) pseudo-first-order and (ii) pseudo-second-order kinetic models, were applied to test the experimental data. The latter provided the best correlation of the experimental data compared to the pseudo-first-order model.

Effect of CuO on the Thermal Stability of Polyaniline Nanofibers

Abstract Direct evidence of the control of thermal stability of polyaniline (PANI) nanofibers is reported by systematically varying the loadings of CuO in the synthesis process. The addition of Cu was maintained in the range from 0.005 g to 1.0 g. The freshly prepared PANI-CuO composite nanofibers were investigated by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). TGA data showed that the thermal stability of PANI nanofibers was greatly improved when the CuO were added, except for the highest addition of CuO (1.00 g). We also found that 0.01 g loading of CuO is favorable to obtain comparatively more thermally stable PANI than the other amount. The degradation of PANI chains started at 360°C for the PANI-CuO composites obtained at 0.01 g CuO addition, which is the highest temperature compared to PANI and the samples synthesized at other amount of CuO loadings.

Effects of CaO on the Yield and Thermal Properties of PANI Nanofibers

Abstract The control of thermal stability of polyaniline (PANI) nanofibers is reported by systematically varying the loadings of CaO in the range from 0.005 g to 1.0 g. It was found to gradually increase the yield of synthesized PANI nanofibers with the increase of CaO addition. The highest yield, 1.103 g was obtained for 1.00 g loading of CaO. The incorporation of CaO into PANI matrix was revealed by energy-dispersive X-ray spectroscopy (EDX). Thermogravimetric analysis (TGA) data showed that the thermal stability of PANI nanofibers was greatly improved when CaO was added to the system. 1.00 g loading of CaO is favorable to obtain comparatively more thermally stable PANI. The degradation of PANI chains started at 330 °C for the PANI-CaO composites obtained at 1.00 g CaO addition, which is the highest temperature compared to PANI and the samples synthesized at other amount of CaO loadings. Furthermore, the increasing trend of thermal stability was observed with the increasing of CaO loading.

Effects of Preparation Approaches and Oxidizing agents on the Yield, Morphology and Thermal stability of Polyaniline

Abstract Evidence of the control of yield and different morphological features of polyaniline (PANI), along with their higher thermal stability is reported. The syntheses were performed by varying the reaction time from 2 to 6 hours for three different methods using three different oxidizing agents. The freshly prepared PANI was investigated by means of fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The polymer yield was increased with the increasing of reaction time from 2 to 6 h for all oxidants in the synthesis approaches; while the reverse trend was observed for KPS in rapid mixing polymerization and mechanical stirring methods. The highest yield was obtained for 6 h reaction time using APS through mechanical stirring method. FESEM analysis showed the growth of regular and uniform PANI nanoparticles, along with the prevention of secondary growth and agglomeration of primary nanofibers using all three oxidizing agents for sonochemistry and rapid mixing polymerization method, except H2O2 in the case of later technique. However, irregular and agglomerated PANI was found for all oxidants in mechanical stirring method. TGA data showed that PANI synthesized by mechanical stirring method is thermally more stable than those prepared by sonochemistry and rapid mixing polymerization.