Double-template-regulated biomimetic construction and tribological properties of superdispersed calcium borate@polydopamine/cellulose acetate-laurate nanocomposite.

Herein, a novel superdispersed calcium borate@polydopamine/cellulose acetate-laurate nanocomposite (CTAB-CB@PDA/CAL) is successfully synthesized by a double-template-regulated biomimetic mineralization strategy using PDA/CAL as a hard template and cetyltrimethylammonium bromide (CTAB) as a soft template and surface hydrophobic modifier. The results show that CB can grow uniformly on the CAL surface, and CTAB can improve the hydrophobicity of CTAB-CB@PDA/CAL due to the synergistic effect of the double templates, which contributes to the enhanced dispersibility and long-term dispersion stability of CTAB-CB@PDA/CAL in poly-alpha-olefin (PAO) base oil. Furthermore, CB can rapidly enter the friction interface due to the long substituents of CTAB and CAL, so CTAB-CB@PDA/CAL used as a lubricant additive in PAO base oil exhibits superior tribological performance compared to CB, CB/CAL, and CB@PDA/CAL.

Fast-thermoresponsive carboxylated carbon nanotube/chitosan aerogels with switchable wettability for oil/water separation.

The use of aerogels to selectively recover oil from oily wastewater is effective but challenging. In this study, a new carboxylated carbon nanotube/chitosan aerogel (CCNT/CA) with switchable wettability was developed as a smart adsorbent for fast oil absorption and oil recovery. Vinyltrimethoxysilane and thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto the surface of the CCNT/CA skeleton, and the resulting smart aerogel (PNI-Si@CCNT/CA) exhibited temperature responsiveness. PNI-Si@CCNT/CA exhibited an excellent reversible conversion between hydrophilicity and hydrophobicity when the temperature was changed to below or above the lower critical solution temperature (LCST) of PNIPAAm (~32 °C). Most importantly, CCNT significantly increased the oil absorption capacity, improved the mechanical properties, accelerated phonon conduction, enhanced thermal conductivity (80.57 mW m-1 K-1), improved the temperature response rate, shortened the oil desorption time (15 min), and improved the oil/water separation efficiency of PNI-Si@CCNT/CA because a strong interface interaction occurred between CCNT and chitosan. Moreover, PNI-Si@CCNT/CA absorbed oil at 45 °C and released the absorbed oil at 25 °C. It maintained its good adsorption performance after 15 cycles, and this was ascribed to its excellent mechanical properties and stable structure.

A stepwise processing strategy for treating highly acidic wastewater and comprehensive utilization of the products derived from different treating steps.

A stepwise processing strategy, including initial neutralization, chemical mineralization, and complete neutralization treating steps, was developed to effectively treat and utilize the highly acidic wastewater derived from titanium dioxide production. Approximately 94.6% of SO42-, 100% of Fe, and most of other metals were recovered to produce white gypsum, schwertmannite, and Fe0/Fe3O4@biochar (Fe0/Fe3O4@BC) composite in the corresponding treating steps. The resulting effluent with neutral pH and a small amount of metal ions could be discharged to general sewage treatment plant for further processing. Schwertmannite was applied as a heterogeneous Fenton-like catalyst to stimulate H2O2 to produce active radicals for effective degradation and mineralization of methyl orange (MO) in solution. The MO removal of 100% and total organic carbon removal of 91.1% were achieved in schwertmannite/H2O2 reaction system, and schwertmannite exhibited good stability and reusability. Fe0/Fe3O4@BC composite was applied to remove Cr(VI), with the adsorption capacity of 67.74 mg g-1. The removal of Cr(VI) using Fe0/Fe3O4@BC composite was a chemisorption process, including the adsorption of Cr(VI), reduction of Cr(VI) to Cr(III), and co-precipitation of Cr(III)/Fe(III) oxides/hydroxides. This stepwise treating strategy is a promising technology for effective treatment of highly acidic industrial wastewater and comprehensive utilization of the related products.

Preparation of sugarcane bagasse succinate/alginate porous gel beads via a self-assembly strategy: Improving the structural stability and adsorption efficiency for heavy metal ions.

Sugarcane bagasse, a kind of agricultural waste, was esterified by mechanical activation-assisted solid phase reaction with succinic anhydride as esterifying agent to prepare SB succinate (SBS) with rich carboxyl and ester functional groups. The layer-by-layer (LbL) self-assembly technology was used to prepare SBS/alginate (Alg) porous gel beads (SAPGB) with outstanding mechanical strength and desired porous structure from external surface to interior through the formation of gel network structure of SBS/Ca2+/Alg. The adsorption kinetics and isotherm indicated that the adsorption of metal ions onto SAPGB followed the pseudo-second-order kinetics and Langmuir isotherm mode (Qmax = 354.60 and 176.36 mg g-1 for Pb2+ and Cd2+, respectively). The adsorption behavior of SAPGB for metal ions was mainly amonolayer chemical adsorption process. The adsorption was fast and reached equilibrium within 60 min, ascribed to rapid diffusion from porous surface into internal pores. In addition, the stable SAPGB adsorbent exhibited excellent regeneration performance.

Nitrogen-Doped Hollow Copolymer Tube via Template-Free Asynchronous Polymerization with Highly Selective Separation of Hydrophilic Dipeptide for Enhancing Inhibitory Activity of Angiotensin Converting Enzyme.

A N-doped hollow copolymer tube (NHCT) was fabricated via template-free one-pot asynchronous polymerization strategy. Discrepancies of monomer polymerization speed and their hydrophilic-hydrophobic interaction resulted in the assembly of a hollow tube having inner diameter and double wall thickness of ∼230 and 40 nm, respectively. The formation and growth mechanism of NHCT analyzed via advanced characterization revealed that the unique growth processes tuned a demarcating surface layer between inner (hydrophilic) and outer (hydrophobic) layers. The screening and recognition ability of NHCT were determined for two specific dipeptides (WW and RR) possessing great discrepancies in hydrophilicity and angiotensin converting enzyme inhibitory (ACE-I) activity. NHCT realized high adsorption capacity (1.57 mmol/g) and selectivity (∼1274) for hydrophilic dipeptide RR (low ACE-I activity) from the mixture of RR/WW. As a result, ACE-I activity for residual solution were enhanced about 4.1 times as compared to original solution from natural silkworm pupae protein hydrolysate. Awarding to these results and its facile and discerning ability, NHCT can be envisioned to be of great value for the separation of small functional peptides from a natural edible source.

Effective treatment and utilization of hazardous waste sulfuric acid generated from alkylation by lignocellulose ester-catalyzed oxidative degradation of organic pollutants.

Alkylation reaction catalyzed by concentrated H2SO4 generates hazardous waste H2SO4 containing a large amount of organic pollutants. This study focused on effective utilization and treatment of the waste H2SO4 for simultaneous consumption of H2SO4 and deep oxidative degradation of the organics. The waste H2SO4 could completely react with magnesium oxide ore to prepare crude MgSO4 solution, and the organic pollutants in the solution were deeply degraded and mainly mineralized to H2O and CO2 with H2O2 as oxidant and sugarcane bagasse citrate (SBC), a kind of lignocellulose ester, as catalyst. The total amount of acidic groups of SBC significantly affected its catalytic activity, attributing to that these oxygen-containing functional groups adsorbed and immobilized metal ions on SBC to form catalytic active sites, which could activate and catalyze H2O2 to generate •OH and HO2• radicals for effective degradation of the organics. The resulting purified MgSO4 solution with color removal of 93.71% and total organic carbon removal of 85.89% under optimum catalytic reaction conditions was used to produce qualified MgSO4∙7H2O product. These results highlighted the feasibility of using lignocellulose ester as effective catalyst for deep oxidative degradation of hazardous organic pollutants.

Damaged starch derived carbon foam-supported heteropolyacid for catalytic conversion of cellulose: Improved catalytic performance and efficient reusability.

To develop an efficient heterogeneous catalyst with good stability and reusability for catalytic conversion of cellulose to platform compounds, carbon foam (CF) was used to immobilize phosphotungstic acid (HPW) to prepare CF-supported HPW (HPW/CF) catalyst. Three-dimensional CF was prepared by carbonization of bread (precursor of CF) with mechanical activation (MA)-damaged starch, gluten protein, and yeast as materials. CF30 (30 wt% of gluten protein) exhibited good mechanical strength, relatively high specific surface area, and desired hierarchical porous structure. HPW was successfully anchored onto CF30 by grafting to prepare HPW/CF30 catalyst, which could effectively catalyze the hydrolysis of cellulose to produce glucose, especially for the hydrolysis of MA-pretreated cellulose with small granules and amorphous structure. The affinity between free hydroxyl groups of MA-pretreated cellulose and oxygen-containing groups of CF30 enhanced the catalytic efficiency of HPW/CF30. In addition, HPW/CF30 catalyst exhibited good reusability and was easily separated from reaction system for recycling.

Overcoming biomass recalcitrance by synergistic pretreatment of mechanical activation and metal salt for enhancing enzymatic conversion of lignocellulose.

BACKGROUND: Due to biomass recalcitrance, including complexity of lignocellulosic matrix, crystallinity of cellulose, and inhibition of lignin, the bioconversion of lignocellulosic biomass is difficult and inefficient. The aim of this study is to investigate an effective and green pretreatment method for overcoming biomass recalcitrance of lignocellulose. RESULTS: An effective mechanical activation (MA) + metal salt (MAMS) technology was applied to pretreat sugarcane bagasse (SCB), a typical kind of lignocellulosic biomass, in a stirring ball mill. Chlorides and nitrates of Al and Fe showed better synergistic effect with MA, especially AlCl3, ascribing to the interaction between metal salt and oxygen-containing groups induced by MA. Comparative studies showed that MAMS pretreatment effectively changed the recalcitrant structural characteristics of lignocellulosic matrix and reduced the inhibitory action of lignin on enzymatic conversion of SCB. The increase in hydroxyl and carboxyl groups of lignin induced by MAMS pretreatment led to the increase of its hydrophilicity, which could weaken the binding force between cellulase and lignin and reduce the nonproductive binding of cellulase enzymes to lignin. CONCLUSIONS: MAMS pretreatment significantly enhanced the enzymatic digestibility of polysaccharides substrate by overcoming biomass recalcitrance without the removal of lignin from enzymatic hydrolysis system.

Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties.

Acylated lignins with substituents consisting of different lengths of carbon chains were prepared by a mechanical activation-assisted solid phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor. The structures and properties were analyzed by UV/Vis, FTIR, NMR, SEM, DSC, and TG. The results showed that the acylated lignins were successfully prepared with either non-cyclic or cyclic anhydrides as the acylating agents. Both aliphatic hydroxyl and phenolic hydroxyl groups of lignin reacted with non-cyclic anhydrides, and different reactivity of acylating agents resulted in different relative contents of phenolic and aliphatic substituents in the products. The reactivity of the cyclic anhydrides was weaker than that of the non-cyclic anhydrides, and the reactivity of the acylating agents decreased with increasing carbon chain length and unsaturated bonds of acyl groups. All of the acylated lignins except maleylated lignin had a lower glass transition temperature (Tg) than the original lignin. The acylated lignins prepared with non-cyclic anhydrides had better thermal stability than original lignin, and the thermal stability increased, but Tg decreased with an increasing chain length of the acyl groups. The acylated lignins prepared with cyclic anhydrides had higher a Tg than those with non-cyclic anhydrides with the same carbon number, and the thermal stability was not obviously improved.

Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin.