Chang Sun

Modification of microcrystalline cellulose with pyridone derivatives for removal of cationic dyes from aqueous solutions

Microcrystalline cellulose (MCC) was modified with pyridone derivatives such as pyridone diester (PDE) and pyridone diacid (PDA) by using succinic acid anhydride as a linker. The modified MCCs were characterized by the fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, elemental analysis and solid state 13C NMR. The adsorption capacities of the modified MCCs to cationic dyes were examined by using methylene blue (MB) as a model dye. It was found that the kinetic adsorption data followed the pseudo-second-order kinetic model, and the adsorption equilibriums were reached less than 10xa0min. The isothermal adsorption data were fitted with the Langmuir isotherm model very well, from which the maximum adsorption capacities of the MCCs modified with PDE and PDA were determined to be 101.01 and 142.86xa0mg/g, respectively. Further investigation showed that the modified MCCs were pH-dependent for adsorption of MB in aqueous solutions. The modified MCCs could be used for removal of MB from an aqueous solution at pH 8, and reused by regeneration in an acidic solution. It was tested that the modified MCCs had a high reusability for removal of MB from aqueous solutions, and still maintained high adsorption capacities even after multiple cycles of desorption–adsorption processes. Hence, the MCCs modified with PDE and PDA could be an effective and efficient approach to removal of cationic dyes from aqueous solutions.

Analysis of factors affecting the performance of activated peroxide systems on bleaching of cotton fabric

AbstractnA screening experiment was designed to investigate the possible factors affecting the performance of activated peroxide systems (APSs) on bleaching of cotton fabric. The design of experiment comprised thirteen factors such as type of bleach activator (BA), concentration of bleach activator ([BA]), molar ratio of hydrogen peroxide to bleach activator ([H2O2]:[BA]), type of peroxide stabilizer (PS), concentration of peroxide stabilizer ([PS]), type of wetting agent (WA), concentration of wetting agent ([WA]), pH value of bleach bath (pH), bleaching temperature (T), bleaching time (t), liquor-to-goods ratio, cotton substrate (C), and water quality (W). The bleaching performance of APSs was accessed by measuring the degree of whiteness of bleached cotton fabric which was defined as the response factor for statistical analysis. The screening analysis revealed that C was the most significant factor affecting the performance of APSs on bleaching of cotton fabric, followed by T, BA, [BA], pH, PS, and [H2O2]:[BA]. Additionally, two-factor interactions were found as well between C and T, T and pH, C and BA, C and [BA], T and [BA], W and [PS], C and PS, and pH and [H2O2]:[BA]. These significant main effects and two-factor interactions were interpreted in details for a better understanding of the performance of APSs on bleaching of cotton fabric. The findings of this study are valuable for further establishment and optimization of APSs for low-temperature bleaching of cotton fabric.

Performance modelling of the TBCC-activated peroxide system for low-temperature bleaching of cotton using response surface methodology

AbstractnIn this study, an activated peroxide system was established for low-temperature bleaching of cotton by incorporating N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC), hydrogen peroxide (H2O2) and sodium bicarbonate (NaHCO3) into an aqueous solution. The bleaching performance was modelled by response surface methodology based on a central composite rotatable design of experiment, in which concentration of TBCC ([TBCC]), concentration of NaHCO3 ([NaHCO3]), temperature (T) and time (t) were four independent variables, and the degree of whiteness (DoW) of bleached cotton was measured as the response variable. For each individual bleaching experiment, TBCC and H2O2 were used in a molar ratio of 1:1.1 and NaHCO3 in a molar amount greater than that of H2O2 for the purpose of driving reactions to completion. A reduced quadratic model (RQM) was constructed using regression analysis with backward elimination, which was used to conduct a practical low-temperature bleaching process for cotton. In comparison to the typical conventional peroxide system, the TBCC-activated peroxide system based on the RQM predication provided cotton with an equivalent DoW and slightly inferior water absorbency, resulted in no apparent damage to cotton fibers, but worked under much milder conditions. This study provides useful insights into scaling up the TBCC-activated peroxide system for low-temperature bleaching of cotton.

X-ray photoelectron spectroscopy analysis of cotton treated with the TBCC/H2O2/NaHCO3 system

N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) was used as a bleach activator for activation of hydrogen peroxide (H2O2) in aqueous solution with the addition of sodium carbonate (NaHCO3). The TBCC/H2O2/NaHCO3 system was applied for treatment of cotton greige fabric at 60℃ in comparison with the conventional H2O2/NaOH system for treatment of cotton greige fabric at 95℃. Experimental results showed that the TBCC/H2O2/NaHCO3 system was effective for improving the degree of whiteness, reducing the fiber damage, and improving the water absorbency of cotton fabric. For understanding the treatment performance of the TBCC/H2O2/NaHCO3 system, X-ray photoelectron spectroscopy (XPS) was applied to analyze the surface elemental composition of cotton greige fabric before and after treatment. C 1s XPS spectra and quantitative analysis revealed that the TBCC/H2O2/NaHCO3 system improved the water absorbency of cotton fabric by removing hydrophobic matters as well as by oxidizing coloring matters and cellulose. The hexane extractions and scanning electron microscopy images indicated that the TBCC/H2O2/NaHCO3 system most likely removed the hydrophobic matters from cotton fabric in a “layer-by-layer” mode, which limited the cellulose backbones exposed for XPS analysis but allowed water to penetrate into cotton fibers.

Pilot-plant investigation on low-temperature bleaching of cotton fabric with TBCC-activated peroxide system

Cotton fabric was bleached at a pilot-plant scale with the activated peroxide system based on N-[4-(triethylammoniomethyl) benzoyl] caprolactam chloride (TBCC). The performance of the TBCC-activated peroxide system on low-temperature bleaching of cotton fabric was evaluated by measuring the degree of whiteness, degree of polymerization, water absorbency, extractable contents, and dyeing properties of bleached cotton fabrics. For comparison purpose, cotton fabric was also bleached at the same pilot-plant scale with a traditional hydrogen peroxide system using a standard recipe. It was found that the pilot-plant bleaching with the TBCC-activated peroxide system resulted in a comparable degree of whiteness and a slightly lower water absorbency of cotton fabric but no apparent fiber damage. The bleached cotton fabric could meet requirements for trichromatic reactive dyeing. The investigation on resource utilization revealed that the pilot-plant bleaching of cotton fabric with the TBCC-activated peroxide system could save 60% water, 38% steam and 27% electric power in comparison with the traditional hydrogen peroxide system. These pilot-plant results are of great importance for further scaling up the TBCC-activated peroxide system to full-scale commercial production.

Preparation of a cellulosic adsorbent by functionalization with pyridone diacid for removal of Pb(II) and Co(II) from aqueous solutions

A cellulosic adsorbent (PDA–MCC) was prepared by halogenation of microcrystalline cellulose (MCC) and functionalized with pyridone diacid (PDA) for removing lead and cobalt ions from aqueous solutions. PDA–MCC was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and thermal gravimetric analysis. The performance of PDA–MCC in removing lead and cobalt ions was examined by investigating the adsorption behaviors of lead and cobalt ions on PDA–MCC. Results from the adsorption of lead and cobalt ions on PDA–MCC showed that the adsorption kinetics followed the pseudo-second-order kinetic model, and the adsorption isotherms could be described by the Langmuir model. The maximum adsorption capacities of PDA–MCC towards lead and cobalt ions were determined to be 177.75 and 122.70xa0mg/g, respectively, which are greater than those of most reported cellulosic adsorbents. The reusable experiment showed that PDA–MCC could be regenerated in an acid solution, and had the adsorption capacities remained greater than 75% even after five cycles of regeneration.