Amino-functionalized cellulose composite for efficient simultaneous adsorption of tetracycline and copper ions: Performance, mechanism and DFT study.

A novel cellulose composite (denoted as PEI@MMA-1) with porous interconnected structure was prepared by adsorbing methyl cellulose (MC) onto microcrystalline cellulose (MCC) and cross-linking polyethyleneimine (PEI) with MCC by the action of epichlorohydrin, which had the excellent adsorption property, wettability and elasticity. The performances of PEI@MMA-1 composite for removing tetracycline (TC), Cu2+ and coexistent pollutant (TC and Cu2+ mixture) were systematically explored. For single TC or Cu2+ contaminant, the maximum adsorption capacities were 75.53 and 562.23 mg/g at 30 °C, respectively, while in the dual contaminant system, they would form complexes and Cu2+ could play a "bridge" role to remarkably promote the adsorption of TC with the maximum adsorption capacities of 281.66 and 253.58 mg/g for TC and Cu2+. In addition, the adsorption kinetics, isotherms and adsorption mechanisms of single-pollutant and dual-pollutant systems have been thoroughly investigated. Theoretical calculations indicated that the amide group of TC molecule with the assistance of Cu2+ interacted with the hydroxyl group of PEI@MMA-1 composite to enhance the TC adsorption capacity. Cycle regeneration and fixed bed column experiments revealed that the PEI@MMA-1 possessed the excellent stability and utility. Current PEI@MMA-1 cellulose composite exhibited a promising application for remediation of heavy metals and antibiotics coexistence wastewater.

Preparation of biodegradable composite films based on carboxymethylated holocellulose from wheat straw.

Holocellulose was extracted from wheat straw and catalytically transformed into carboxymethylated holocellulose (CMHCS) to prepare a biodegradable composite film. By changing the type and amount of catalyst, the carboxymethylation of the holocellulose was optimized with respect to the degree of substitution (DS). A high DS of 2.46 was achieved in the presence of a cocatalyst composed of polyethylene glycol and cetyltrimethylammonium bromide. The effect of DS on the properties of CMHCS-derived biodegradable composite films was further investigated. Compared to pristine holocellulose, the mechanical properties of the composite film were significantly improved and increased with increasing DS. The tensile strength, elongation at break, and Young's modulus increased from 6.58 MPa, 51.4 %, and 26.13 MPa for the unmodified holocellulose-based composite film to 14.81 MPa, 89.36 %, and 81.73 MPa for the film derived from the CMHCS with a DS of 2.46. The biodegradability of the composite film was assessed under soil burial biodisintegration conditions and reached 71.5 % degradation after 45 d. Additionally, a possible degradation process for the composite film was proposed. The results indicated that the CMHCS-derived composite film has good comprehensive performance, and CMHCS is expected to be applied in the field of biodegradable composite materials.

Immobilization CoOOH nanosheets on biochar for peroxymonosulfate activation: Built-in electric field mediated radical and non-radical pathways.

The strong electron interaction between metal oxide-carbon-based catalyst components plays a vital role in the peroxymonosulfate (PMS) activation for pollutant degradation. Herein, a novel CoOOH nanosheets anchored on rape straw-derived biochar (BC) surface (labeled as CoOOH/BC) as an efficient PMS activator toward degrading sulfamethoxazole (SMX) was synthesized. Experimental results indicated that integrating CoOOH nanosheets on the BC surface could inhibit CoOOH aggregation to increase the specific surface areas, exert a component synergistic effect to enhance activation degradation activity, and improve the catalyst stability. As a result, a 96 % degradation efficiency of SMX was achieved within 20 min over 20 wt% CoOOH/BC composite catalyst under the optimal conditions. Density functional theory (DFT) calculations disclosed that a built-in electric field (BIEF) pointing from BC to CoOOH was constructed at their interface, which could mediate PMS activation for reactive oxygen species (ROS) generation and induce direct electron transfer from SMX to PMS, resulting in efficient SMX degradation via both radical and non-radical pathways. Moreover, quenching experiments and electron paramagnetic resonance (EPR) measurements confirmed that single oxide (1O2) and superoxide radical (O2·-) are the dominant active species in the current system. Additionally, the possible SMX degradation routes were reasonably proposed based on liquid chromatography-mass spectrometry (LC-MS) results. This work provides an in-depth understanding of the role of BIEF in PMS activation, and expands the application of biochar-based materials in the field of environmental remediation.

Anaerobic digestion of sulphate wastewater mediated by biochar.

In this paper, the influences of biochar on the anaerobic digestion of sulphate wastewater, including the COD removal rate, methane yield, intermediate products and the change of microbial community structure, were investigated. The results showed that sulphate could promote the anaerobic digestion with the SO42-/COD ratio increasing from 0 to 0.1, while the activity of MPB was inhibited, which led to the decrease of COD removal rate and methane yield with the SO42-/COD ratio increasing from 0.1 to 2. At 1 g biochar loading, 344.97 mL CH4/gCODremoval was obtained compared with the control group (220.70 CH4/gCODremoval) at 2 of SO42-/COD. Biochar could also reduce the secondary accumulation of NH4+-N and TVFA. Meanwhile, methanogenic microorganisms were selectively enriched especially for methanobacterium, methanosaeta and methanolinea, while the growth of SRB was inhibited with biochar addition.

Enhancing anaerobic digestion of sulphate wastewater by adding nano-zero valent iron.

In this paper, the effects of nano-zero valent iron (nZVI) on anaerobic digestion of sulphate wastewater with different SO42-/COD ratios, including the COD removal rate, methane yield, intermediate products and the change of microbial community structure, were investigated. The results showed that nZVI could effectively enhance the treatment efficiency and methane yield. Compared with the control group without nZVI, the methane yield increased from 348.6833 to 1007.05 mL CH4/gCODremoval with 4 g nZVI loading at SO42-/COD = 0.1. nZVI could make electron flow from sulphate reduction to methane production, which increased methane yield even at high sulphate concentration. The microbial community analysis showed that adding nZVI could increase the abundance of acetoclastic methanogens, which accelerated hydrolysis acidification.

Unleashing the power within short-read RNA-seq for plant research: Beyond differential expression analysis and toward regulomics.

RNA-seq has become a state-of-the-art technique for transcriptomic studies. Advances in both RNA-seq techniques and the corresponding analysis tools and pipelines have unprecedently shaped our understanding in almost every aspects of plant sciences. Notably, the integration of huge amount of RNA-seq with other omic data sets in the model plants and major crop species have facilitated plant regulomics, while the RNA-seq analysis has still been primarily used for differential expression analysis in many less-studied plant species. To unleash the analytical power of RNA-seq in plant species, especially less-studied species and biomass crops, we summarize recent achievements of RNA-seq analysis in the major plant species and representative tools in the four types of application: (1) transcriptome assembly, (2) construction of expression atlas, (3) network analysis, and (4) structural alteration. We emphasize the importance of expression atlas, coexpression networks and predictions of gene regulatory relationships in moving plant transcriptomes toward regulomics, an omic view of genome-wide transcription regulation. We highlight what can be achieved in plant research with RNA-seq by introducing a list of representative RNA-seq analysis tools and resources that are developed for certain minor species or suitable for the analysis without species limitation. In summary, we provide an updated digest on RNA-seq tools, resources and the diverse applications for plant research, and our perspective on the power and challenges of short-read RNA-seq analysis from a regulomic point view. A full utilization of these fruitful RNA-seq resources will promote plant omic research to a higher level, especially in those less studied species.

Enhanced catalytic performance of CuCr/ZSM-5 catalyst by chemical vapour deposition for trichloroethylene oxidation.

The CuCr mixed oxides catalysts supported on ZSM-5 zeolite (CuCr/ZSM-5) were synthesized via metal organic chemical vapour deposition (MOCVD) method for catalytic oxidation of trichloroethylene (TCE). SEM, XRD, BET, H2-TPR, NH3-TPD and XPS were tested. The active components were dispersed uniformly over the surface of ZSM-5 zeolite. The catalytic experimental results exhibited that the CuCr/ZSM-5 exhibited the best catalytic performance for TCE oxidation with 90% of TCE at 338°C and the concentration of C2Cl4 decreased compared with Cu/ZSM-5 and Cr/ZSM-5. The possible reason is that CuCr/ZSM-5 has superior reducibility, higher Cu2+ surface concentration as well as more surface oxygen.

Investigation on the Preparation of Rice Straw-Derived Cellulose Acetate and Its Spinnability for Electrospinning.

Rice straw-derived cellulose (RSC) with purity of 92 wt.% was successfully extracted from rice straw by a novel and facile strategy, which integrated the C2H5OH/H2O autocatalytic process, dilute alkali treatment and H2O2 bleaching process. Influencing factors of the cellulose extraction were systematically examined, such as ethanol concentration, alkali concentration, H2O2 bleaching process and so on; the optimal extraction conditions of cellulose was determined. A series of rice straw-derived cellulose acetate (RSCA) with different degree of substitution (DS) were prepared by the acetylation reaction; the effects of Ac2O/cellulose ratio, reaction temperature and reaction time on the acetylation reaction were investigated. Results of FTIR and XRD analysis demonstrated that highly purified RSC and RSCA were prepared comparing with the commercial cellulose and cellulose acetate. Solubility analysis of RSCA with different DS indicated as-prepared RSCA with DS of 2.82 possessed the best solubleness, which was suitable for electrospinning. Moreover, the flexible RSCA fibrous membrane was easily fabricated by a facile electrospinning method. Our proposed method provided a strategy for realizing the high-value utilization of waste rice straw resource, as prepared RSC and RSCA can be used as chemical raw material, and electrospun RSCA fibrous membrane has various applications in medical materials, food packaging, water purification and so on.

Influence of surfactant on CO2 adsorption of amine-functionalized MCM-41.

Concerning the increasing greenhouse effect, the development of efficient CO2 adsorbents is very important. In this study, the influence of surfactant on the adsorption performance of amine-functionalized MCM-41 was analysed. The results showed that the residual amount of surfactant in MCM-41 was gradually decreased with the increase of calcination temperature which improved the pore structure. The maximum adsorption capacity (5.495 mmol/g) appeared at PEI-MCM-41-100°C indicated that the adsorption capacity could be improved under the function of surfactant. By calculating the diffusion coefficient of CO2 adsorption process in PEI-MCM-41-100/200/300/400/550°C, the diffusion resistance of CO2 was the lowest in PEI-MCM-41-100°C, which directly proved that the synergism of surfactant and organic amine could reduce the diffusion resistance of CO2 in the pore.

Oxidative conversion of lignin isolated from wheat straw into aromatic compound catalyzed by NaOH/NaAlO2.

Lignin was isolated from wheat straw via organosolv process and further transferred to monophenolic compounds via oxidative conversion. Wheat straw lignin (WSL) with purity at 91.4 wt% was acquired in the presence of heterogeneous and recyclable catalyst of Amberlyst-45. WSL was characterized by infrared spectrometer (IR), nuclear magnetic resonance spectroscopy (NMR) including 1H NMR and 13C NMR spectra. The results showed that WSL possesses typical syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) units, and it is mainly composed of S and G units. The product distribution was dependent on the composition of WSL. Derivatives from S and G units were found to be the main products. The oxidative conversion of WSL was performed by varying oxidant and catalyst. Both the formation of monophenolic compounds and aromatic aldehydes were enhanced by combining oxidants and catalysts. The composite catalyst composed of NaOH/NaAlO2 was effective for the oxidation of WSL in the presence of nitrobenzene and atmospheric pressure air. The total yield of monophenolic compounds reached up 18.1%, and yields at 6.3 and 5.7% for syringaldehyde and vanillin were achieved, respectively.

Preparing high purity white carbon black from rice husk.

In this paper, rice husk (RH) was used as raw material to prepare white carbon black, and the key technological parameters of preparing white carbon black from RH were studied through single-factor test, orthogonal experiment, and response surface analysis. Meanwhile, the characteristic of white carbon black was also analyzed. Through orthogonal experiment analysis, it was confirmed that the order of factors affecting the purity of white carbon black was calcination temperature > alkali treatment time > final pH > surfactant. Based on the response surface optimization analysis, the optimum parameters for preparation of white carbon black were as follows: calcination temperature 610°C, alkali treatment time of 2.3 hr, final pH of 10, CTMAB was used as the surfactant. Under this condition, the purity of silica prepared could be reached to 99.39%, and the particle size was uniform, spherical, and well dispersed, which satisfied the requirements of GB/T 34698-2017 standard.

Synthesis of 5-hydroxymethyl furfural from cellulose via a two-step process in polar aprotic solvent.

The synthesis of 5-hydroxymethyl furfural (HMF) from cellulose via a two-step process was investigated. To optimize reaction conditions, the separate conversion of cellulose and glucose was first performed in tetrahydrofuran (THF) and N, N-dimethylformamide (DMF) via a one-step process using hosphotungstic acid (PHA) as catalyst. The direct conversion of cellulose to HMF was then performed via the two-step process. The first step and the second step were carried out in THF and the mixture solvent composed of THF/DMF, respectively. Cellulose was converted to HMF and glucose in the first step in THF. Both of cellulose and the as-formed glucose were then converted to HMF in the second step. The conversion of cellulose to HMF and glucose were significantly improved by the two-step process, and the total yield of HMF and glucose was elevated from 52.1 to 97.0%. A possible mechanism for the formation of HMF from cellulose via the two-step process was also proposed.

Amberlyst 15 as a new and reusable catalyst for the conversion of cellulose into cellulose acetate.

The acetylation of cellulose using sulfonated Amberlyst 15 as a new and reusable catalyst was investigated. Optimization of the acetylation process was carried out by variation in the amount of added catalyst, acetic acid, and acetic anhydride as well as the reaction conditions, which includes reaction time and reaction medium. Cellulose acetate, with a degree of substitution (DS) value of 2.38 and yield of 54.1%, was obtained under the optimized conditions and characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis-derivative thermogravimetry (TGA-DTG), and differential scanning calorimetry (DSC). The sulfonated polymer catalyst could be easily recovered by centrifugation after acetylation. Both the fresh and recovered catalysts were characterized by means of FTIR, TGA-DTG, DSC, and scanning electron microscopy (SEM), and the recovered catalyst could be successfully reused without further treatment. It was found that Amberlyst 15 possessed excellent catalytic stability, no significant changes in the DS values, and consistent yields of cellulose acetate observed over four reaction cycles.

[Direct determination of trace lead in chestnut by graphite furnace atomic absorption spectrometry with slurry sampling].

A method for the direct determination of trace lead in chestnut by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) with slurry sampling was developed in the present paper. Ammonium ortho-phosphate was used as a matrix modifier. The effects of slurry preparation, particle size of sample, matrix modifier, ashing temperature, atomization temperature, and common coexisting components on the determination of lead were studied. Under the optimized operating conditions, the detection limit, the relative standard deviation (RSD), and the recoveries of standard addition for this method were 0.47 ng x mL(-1), 6.1% (n = 11) and 90%-106%, respectively.