Efficient adsorption of diclofenac sodium in water by a novel functionalized cellulose aerogel.

In this work, a novel cellulose aerogel (CNC-PVAm/rGO) was fabricated using cellulose nanocrystalline (CNC) modified with polyvinylamine (PVAm) and reduced graphene oxide (rGO). The resultant CNC-PVAm/rGO was then applied for the adsorption of diclofenac sodium (DCF), a typical non-steroidal anti-inflammatory drug. Characterization using ultra-high-resolution field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and the Brunauer-Emmett-Teller surface area revealed that the obtained CNC-PVAm/rGO displayed an evident 3D porous structure, which had an ultralight weight, good recovery, abundant surface functional groups (e.g., -NH2 and -OH), and rGO nanosheets. In addition, the material presented a stable crystal structure and large specific surface area (105.73 m2 g-1). During the adsorption of DCF, the CNC-PVAm/rGO aerogel showed a rather excellent adsorption performance, with a maximum adsorption capacity (qmax) of 605.87 mg g-1, which was approximately 53 times larger than that of the bare CNC aerogel (11.45 mg g-1). The adsorption performance of CNC-PVAm/rGO was also better than that of other reported adsorbents. The adsorption of DCF to CNC-PVAm/rGO obeyed the Langmuir isotherm and pseudo-second-order kinetic models, and underwent a spontaneous exothermic process. Moreover, DCF was easily desorbed from CNC-PVAm/rGO with sodium hydroxide solution (0.1 mol L-1), and the absorbent could be reused four times. The introduction of PVAm and rGO to the CNC-PVAm/rGO aerogel also greatly enhanced electrostatic interactions, π-π interactions, and hydrophobic effects. These enhancements significantly promoted the hydrogen bonding interactions between the DCF molecules and CNC-PVAm/rGO, thus resulting in a large improvement in the adsorption performance of the aerogel.

Synergistic activation of persulfate by Fe-based perovskite photocatalysis for alkali lignin degradation in pulp and paper wastewater.

A synergistic photocatalytic system based on Fe-based perovskite with persulfate was constructed for alkali lignin (AL) degradation in pulp and paper wastewater. The degradation performance and mechanism on AL were carried out under ambient temperature and pressure, accompanied by visible light irradiation. The results showed that the synergistic photocatalytic system exhibited much better performance on AL degradation than the single catalytic system. The degradation efficiency reached 73.5% under the optimal conditions and was constant at around 65% over the pH range from 2 to 8. A significant escalation of the AL degradation was observed at pH 10, reaching 80.1%. The photogenerated holes, 1O2 and SO4-·, generated by the system were involved in the degradation, and the holes played a dominant role. During the degradation process, the efficient promotion of cleavage events in lignin methoxy, ß-O-4 bond, and benzene ring was observed. Consequently, the depolymerization process led to the generation of high-value compounds, namely p-hydroxybenzaldehyde and vanillin. Remarkably, the yields of the high-value compounds in the synergistic photocatalytic system were five times larger than those in the control. This study offered a viable method to activate persulfate for alkali lignin degradation and to achieve a mutually beneficial strategy for wastewater treatment and recycling.

Efficient dispersive solid phase extraction of trace nitrophenol pollutants in water with triazine porous organic polymer modified nanofiber membrane.

Detecting trace endocrine disruptors in water is crucial for evaluating the water quality. In this work, a innovative modified polyacrylonitrile@cyanuric chloride-triphenylphosphine nanofiber membrane (PAN@CC-TPS) was prepared by in situ growing triazine porous organic polymers on the polyacrylonitrile (PAN) nanofibers, and used in the dispersive solid phase extraction (DSPE) to enrich trace nitrobenzene phenols (NPs) in water. The resluted PAN@CC-TPS nanofiber membrane consisted of numerous PAN nanofibers cover with CC-TPS solid spheres (∼2.50 µm) and owned abundant functional groups, excellent enrichment performance and good stability. In addition, the method based on PAN@CC-TPS displayed outstanding capacity in detecting the trace nitrobenzene phenols, with 0.50-1.00 µg/L of the quantification, 0.10-0.80 µg/L of the detection limit, 85.35-113.55 % of the recovery efficiency, and 98.08-103.02 of the enrichment factor, which was comparable to most materials. Meanwhile, when PAN@CC-TPS was adopted in the real water samples (sea water and river water), the high enrichment factors and recovery percentages strongly confirmed the feasibility of PAN@CC-TPS for enriching and detecting the trace NPs. Besides, the related mechanism of extracting NPs on PAN@CC-TPS mainly involved the synergistic effect of hydrogen bonding, π-π stacking and hydrophobic effect.

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels.

Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).

Insights into efficient adsorption of the typical pharmaceutical pollutant with an amphiphilic cellulose aerogel.

An amphiphilic cellulose aerogel (HCNC-TPB/TMC) was fabricated by grafting 1,3,5-Tris (4-aminophenyl)benzene (TPB) and trimesoyl chloride (TMC) onto the aldehyde nanocellulose through Schiff alkali and substitution reaction. The obtained HCNC-TPB/TMC exhibited good morphology with cellulose fiber and owned abundant hydrophilic amino and carboxyl groups and hydrophobic aromatic groups. The batch adsorption experiments demonstrated that HCNC-TPB/TMC showed excellent adsorption performance (Qmax = 526.32 mg g-1) for sodium diclofenac (DCF), wide pH applicability (4-10) and outstanding stability and reusability. The DCF adsorption obeyed the pseudo-second-order kinetic model and the Langmuir isotherm, and underwent a spontaneous exothermic process. The main adsorption mechanisms involved electrostatic interaction, hydrogen bonds, π-π stacking interaction and hydrophobic effect. Importantly, the introduced carboxyl aromatic groups on TMC could effectively strengthen the hydrogen bonds and the π-π stacking between HCNC-TPB/TMC and DCF.

Efficient extraction of trace organochlorine pesticides from environmental samples by a polyacrylonitrile electrospun nanofiber membrane modified with covalent organic framework.

Detecting and analyzing of the trace organochlorine pesticides (OCPs) in the real water has become a big challenge. In this work, a novel functional electrospun nanofiber membrane (PAN@COFs) was synthesized through the in situ growth of covalent organic frameworks (COFs) on a polyacrylonitrile electrospun nanofiber membranes under room temperature and used in the solid-phase micro-extraction (SPME) to enrich trace organochlorine pesticides (OCPs) in water. The resulted PAN@COFs composite consisted of numerous nanofibers coated ample porous COFs spheres (~ 500 nm) and owned stable crystal structure, abundant functional groups, good stability. In addition, the enrichment experiments clearly revealed that PAN@COFs exhibited rather outstanding performance on adsorbing the trace OCPs (as low as 10 ng L-1) with the enrichment of 482-2686 times. Besides, PAN@COFs displayed good reusability and could be reused 100 times. Notably, in the real water samples (sea water and river water), the high enrichment factors and recovery rates strongly confirmed the feasibility of PAN@COFs for detecting the trace OCPs. Furthermore, due to the synergy of π-π stacking interaction and hydrophobic interaction between the OCPs molecules and PAN@COFs, the OCPs could be efficiently adsorbed on PAN@COFs, even under the extremely low driving force.

Carboxylated cellulose nanocrystals with chiral nematic property from cotton by dicarboxylic acid hydrolysis.

Carboxylated cellulose nanocrystals (CNCs) were produced from cotton linter using a mixture of a dicarboxylic acid (maleic acid or succinic acid) and its corresponding anhydride with or without catalyst in acetic acid as solvent. The low solubilities of these dicarboxylic acids can ease chemical recovery and decrease environmental impact (especailly maleic acid is a U.S. FDA approved indirect food additive (21CFR175-177)) and capital costs compared with the conventional concentrated sulfuric acid hydrolysis for producing CNCs. The dicarboxylic-acid-produced CNCs (DC-CNCs) contained surface carboxyl groups of approximately 0.5 mmol/g, with ranges of dimensions of 50-150 nm in diameter and 50-700 nm in length. Birefringence was observed in the DC-CNC suspensions above critical concentrations. However, fingerprint texture was only observed in the DC-CNC suspensions produced with catalyst p-toluenesulfonic acid. Scanning electron microscopy images of the cross section of DC-CNC films revealed a periodic ordered multilayer structure. DC-CNCs were also produced using recycled dicarboxylic acids.