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.

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 122.70 mg/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.

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 10 min. 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 142.86 mg/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.

•TBBC-activated peroxide system was established for cotton bleaching.•Cotton fabric was most effectively bleached under near-neutral pH conditions.•Whiteness of cotton fabric was optimized at a temperature as low as 50 °C.•TBBC-activated peroxide system was comparable to hot alkaline peroxide system in improving cotton whiteness.Cotton bleaching is traditionally carried out in strongly alkaline solution of hydrogen peroxide (H2O2) at temperatures close to the boil. Such harsh processing conditions can result in extensive water and energy consumptions as well as severe chemical damage to textiles. In this study, an activated peroxide system was established for low-temperature cotton bleaching by incorporating a bleach activator, namely N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) into an aqueous H2O2 solution. Experimental results showed that the TBBC-activated peroxide system exhibited the most effective bleaching performance in a pH range of 6–8 which could be approximated by adding sodium bicarbonate (NaHCO3). The TBBC/H2O2/NaHCO3 system led to rapid bleaching of cotton at a temperature as low as 50 °C. In comparison with the hot alkaline peroxide bleaching system, the TBBC/H2O2/NaHCO3 system provided cotton fabric with an equivalent degree of whiteness, higher degree of polymerization, and slightly lower water absorbency. The new activated peroxide system may provide a more environmentally benign approach to cotton bleaching.

There exists a misunderstanding on the TAED-activated peroxide system in the textile industry that H2O2 used in excess of the stoichiometric amount could produce an addition effect on bleaching of cotton under alkaline conditions. In this study, a critical reinvestigation was carried out on the TAED-activated peroxide system for bleaching of cotton. It was found that the TAED-activated peroxide system achieved its best performance under near-neutral pH conditions. No addition effect was observed when an excessive amount of H2O2 was used under alkaline conditions, which is probably due to the base-catalyzed bimolecular decomposition of peracetic acid and the nucleophilic attack by H2O2 on peracetic acid. NaHCO3 was shown to be a desired alkaline agent for maintaining near-neutral pH for the TAED-activated peroxide system. This study provides new insight into the application of the TAED-activated peroxide system for low-temperature bleaching of cotton under more environmentally benign conditions.Highlights► The TAED-activated peroxide system conducted effective cotton bleaching at near-neutral pH. ► PAA underwent two types of decomposition under alkaline conditions. ► H2O2 in excess of the stoichiometric amount produced no addition effect on cotton bleaching. ► NaHCO3 was the most desired alkaline agent for use in cotton bleaching.

A low-temperature and near-neutral pH bleaching system was conceived for cotton by incorporating TAED, H2O2 and NaHCO3. The TAED/H2O2/NaHCO3 system was investigated and optimized for bleaching of cotton using a central composite design (CCD) combined with response surface methodology (RSM). CCD experimental data were fitted to create a response surface quadratic model (RSQM) describing the degree of whiteness of bleached cotton fabric. Analysis of variance for the RSQM revealed that temperature was the most significant variable, followed by [TAED] and time, while [NaHCO3] was insignificant. An effective system was conducted by adding 5.75 g L−1 TAED together with H2O2 and NaHCO3 at a molar ratio of 1:2.4:2.8 and applied to bleaching of cotton at 70 °C for 40 min. Compared to a commercial bleaching method, the TAED/H2O2/NaHCO3 system provided cotton with comparable degree of whiteness, slightly inferior water absorbency and acceptable dyeability, but had competitive advantage in protecting cotton from severe chemical damage in bleaching.Highlights► The TAED/H2O2/NaHCO3 system was conducted for bleaching of cotton. ► The bleaching performance was investigated and optimized using CCD combined with RSM. ► Temperature was the most significant variable followed by [TAED] and time but [NaHCO3] was insignificant. ► The bleaching system provided cotton with satisfactory degree of whiteness, water absorbency and dyeability. ► The bleaching system had competitive advantage in protecting cotton from severe chemical damage in bleaching.