Facile fabrication of nanocellulose-supported membrane composited with modified carbon nitride and HKUST-1 for efficient photocatalytic degradation of formaldehyde.

As a cellulose-derived material, nanocellulose possesses unique properties that make it an ideal substrate for various functional composite materials. In this study, we developed a novel composite membrane material capable of adsorbing and photo-catalyzing formaldehyde by immobilizing HKUST-1 (copper open framework composed of 1,3,5-benzenetricarboxylic acid) onto NFC (Nano-fibrillated cellulose) membranes and subsequently loading modified carbon nitride. The synthesized CNx@HN composite membrane (consisting of NFC membrane with anchored HKUST-1 and modified g-C3Nx nanosheets) was thoroughly characterized, and its photocatalytic degradation performance towards low concentrations of formaldehyde (3.0 mg/m3) was investigated. The results demonstrated that HKUST-1's porous nature exhibited a concentrated adsorption capacity for formaldehyde, while the modified CNx (Modified g-C3Nx nanosheets) displayed robust photocatalytic degradation of formaldehyde. The synergistic effect of HKUST-1 and modified CNx on the NFC membrane significantly enhanced the efficiency of formaldehyde degradation. Under xenon lamp irradiation, CNx@HN-5 achieved a total removal efficiency of 86.9 % for formaldehyde, with a photocatalytic degradation efficiency of 48.45 %, showcasing its exceptional ability in both adsorption and photocatalytic degradation of formaldehyde. Furthermore, after 10 cycles of recycling, the composite membrane exhibited excellent stability for the photocatalytic degradation process. Therefore, this study presents a green and facile strategy to fabricate nanocellulose-supported composite membranes with great potential for practical applications in formaldehyde degradation.

Diatomite Composited with a Zeolitic Imidazolate Framework for Removing Phosphate from Water.

Adsorption technology based on various adsorbents has been widely applied in wastewater treatment containing phosphate. A novel diatomite adsorbent composited with ZIF-8 (CZD) was developed for removing phosphate from water in this work. The chitosan was used to pre-modify the diatomite so that ZIF-8 could be anchored on the surface of the diatomite solidly and uniformly. The diatomite composited with ZIF-8 was then used to remove phosphate in water by an adsorption process, the process variables such as adsorption time, temperature, pH, and competitive ions were investigated. The electrostatic attraction was the primary mechanism of phosphate removal. The adsorption reached equilibrium within 90 min, and its sorption capacity increased when adsorption time and temperature increased. Especially, CZD had a rapid adsorption rate and 85% of the phosphate in the solution can be adsorbed within the first 10 min. The maximum phosphate adsorption capacities of the modified diatomite reached 13.46, 13.55, and 13.95 mg/g at 25, 35, and 45 °C, respectively. The removal efficiencies of CZD for phosphate were more than 98% and even came up to 100% at 45 °C. The adsorption isotherms fit well with the Langmuir isotherm model. The Freundlich isotherm and Temkin isotherm showed that the adsorption process is physical in nature. The kinetic data of the adsorption process were fitted by the pseudo-second-order kinetics. Thermodynamic parameters indicated that the adsorption process was endothermic. This adsorbent provided an alternative for phosphate removal on account of the high adsorption efficiency in a short time. Therefore, CZD could be a promising and eco-friendly phosphate adsorbent for wastewater treatment.

Diatomite Modified with an Alkyl Ketene Dimer for Hydrophobicity of Cellulosic Paper.

Multifunctionalization of papermaking chemicals is one of the main developing strategies. Fillers and internal sizing agents are often mutually restricted in practice. Therefore, it is feasible to prepare a new papermaking chemical by combining the functions of both. A process of diatomite modified with an alkyl ketene dimer (AKD) was developed in this study. The modified diatomite (AD) can concurrently play the role of a mineral filler and sizing agent in the papermaking process. With the equal dosage of AKD, the AD showed better sizing and retention performance than the commercial AKD emulsion in the case of cationic polyacrylamide (CPAM) and the CPAM/bentonite retention system. The sizing mechanism of the AD can be interpreted to be due to numerous hydrophobic sites and the microsurface structure of the paper sheet caused by the AD. Since ketones were not detected in Fourier-transform infrared spectra of the paper sheet filled by the AD, the chemical reaction may not be indispensable for its sizing performance. What is more, an interesting "sticky" hydrophobicity phenomenon was observed when filling with AD. The approach in this study to prepare the "sticky" hydrophobic paper sheet can find its applications in some nontraditional application fields of cellulosic paper.

Green assembly of high-density and small-sized silver nanoparticles on lignosulfonate-phenolic resin spheres: Focusing on multifunction of lignosulfonate.

In this work, sodium lignosulfonate (SL) was introduced in the hydrothermal preparation of phenol-formaldehyde (PF) resin sphere that was subsequently used as a green reducer and support for synthesis of Ag nanoparticles (Ag NPs). The results showed that the addition amount of SL had a remarkable effect on the size of the SL incorporated PF (SLPF) spheres and the smallest particle size was obtained when 20% of SL (based on phenol mass) was added. The addition of SL increased the surface area and negative charge of SLPF spheres, which enhanced the Ag NPs loading amount accordingly. Moreover, SL also prevented Ag NPs from aggregating effectively, resulting in the high-density loading of small size Ag NPs on the SLPF spheres. Therefore, the as-prepared Ag@SLPF composites exhibited significantly enhanced catalytic activities in the 4-nitrophenol reduction than that of SL-free Ag@PF. Besides, the Ag@SLPF catalyst demonstrated superior recyclability owing to strong anchoring between the Ag NPs and the support. Consequently, the work demonstrates the incorporation of SL enables the green formation of high-density and tunable Ag NPs on the SLPF support and then endows the composite catalyst with enhanced catalytic performance, which presents a promising value-added application of lignosulfonate for functional catalyst preparation.

[Effect of Ca2+ on the Nitrification Activity and the Flocculation and Sedimentation Performances of the Activated Sludge].

Ca2+ is an important microbial growth factor that can affect the activity, flocculation, and sedimentation of activated sludge. In order to study the roles of Ca2+ in the activated sludge system, the activity changes of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were analyzed using the specific oxygen uptake rates (SOURAOB and SOURNOB). The changes in composition and structure of extracellular polymeric substances (EPS) were analyzed using Fourier transform infrared spectroscopy (FTIR) and three-dimensional excitation emission fluorescence spectroscopy (3D-EEM). The effects of Ca2+on the nitrification activity and microbial metabolites were investigated. The results showed that when the Ca2+concentration increased from 0.45 mmol·L-1 to 3 mmol·L-1, SOURAOB and SOURNOB increased from 6.3 mg·(g·h)-1 to 10.4 mg·(g·h)-1 and from 2.3 mg·(g·h)-1 to 3.7 mg·(g·h)-1, respectively. The EPS concentrations increased from 68 mg·g-1 to 93 mg·g-1, and the flocculation ability (FA) of the sludge was improved. When the Ca2+ concentration was higher than 3 mmol·L-1, SOURAOB and SOURNOBboth decreased. The FA was maintained at about 30%, and the particle size of the sludge continued to increase. Based on FTIR analysis, the main components of EPS were always amino, amide Ⅰ, and carboxyl with an increase in Ca2+ concentration. Based on EEM analysis, the composition of loosely-bound (LB)-EPS did not change, and humic acid substances appeared in the tightly-bound (TB)-EPS at low nitrification rates. Low concentrations of Ca2+ promoted nitrification activity and flocculation of the sludge. However, high concentrations of Ca2+ led to a decline in the sludge nitrification activity.

Effects of K+ salinity on the sludge activity and the microbial community structure of an A2O process.

Salt ions are ubiquitous in wastewater and have significant impacts on the microbial activity and nitrogen and phosphorus removal in biological wastewater treatment processes. The effects of KCl salinity on the removal of COD, TN and PO43--P were investigated in a lab-scale A2O process. Meanwhile, the effects of K+ concentration on the composition of extracellular polymeric substances (EPS) and the microbial community structure were demonstrated. The results showed that the pollutant removal efficiencies and the bioactivity of the activated sludge decreased and the EPS content enhanced under high concentration of K+, which resulted in the deterioration of sludge compactness and settleability. The microbial diversity reduced after K+ addition and the microbial community structure was distinct between the system with (10 g L-1 and 40 g L-1) and without K+ addition. The relative abundance of Candidatus-Competibacter, Acinetobacter and Azoarcus decreased in the anoxic zone with the increase of K+ concentration, which might led to the decrease in denitrifying phosphorus removal capacity. However, the relative abundance of some genera of Firmicutes (such as Fusibacter, Acetoanaerobium, Planococcus and Exiguobacterium) increased, which was coincident with the enhanced microbial salt-tolerance capacity. Proteobacteria, Bacteroides, Chloroflexi and Firmicutes were the dominant phyla irrespective of the salinity changed, which guaranteed the removal of organic compounds, nitrogen and phosphorus in salty environment.

[Effect of NaCl Salinity on Extracellular Polymeric Substances and Bioflocculation of Anoxic Sludge in A2/O Process].

In order to improve the biological removal efficiency of nitrogen and phosphorus and bioflocculation performance of salt-containing wastewater, the effect of NaCl salinity on the efficiency of denitrification and phosphorus removal in the anoxic zone of an A2/O process was investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the composition and structure of extracellular polymeric substances (EPS) in activated sludge of the anoxic zone, to discern the effect of salinity on bioflocculation. Results showed that when NaCl salinity was 0-5 g·L-1, flocculation ability (FA) in A2/O anoxic zone was about 44% and the sludge particle size was 45.5 µm. EPS content increased from 52.3 mg·L-1 to 62 mg·L-1 and protein (PN)/polysaccharide (PS) remained at 2.1. When NaCl salinity increased from 10 g·L-1 to 40 g·L-1, bioflocculation of sludge significantly decreased. FA decreased from 40% to 22% and sludge particle size decreased from 43.7 µm to 32.1 µm. EPS content increased from 76.5 mg·L-1 to 101.0 mg·L-1 and PN/PS decreased from 1.5 to 1.3. Based on FTIR analysis, with increase in salinity, the main components of EPS were always amino, amideⅠ, and carboxyl. Based on XPS analysis, increasing salinity led to charge transfer of some groups (such as C, O, and N groups) during the interaction between EPS and Na+, but its form did not change.

[Preparation of Mn-Co/Ceramic Honeycomb Catalyst and Its Performance on Catalytic Ozonation of Hydroquinone].

In order to improve the activity and working life of metal catalysts in the heterogeneous catalytic ozonation of organic wastewater, four kinds of Mn-Co/ceramic honeycomb (CH) catalysts with different mass ratios of Mn and Co were prepared by coating method using cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and manganese nitrate [Mn(NO3)2] as precursors, respectively, and CH as the carrier. The structure of the catalysts was analyzed via X-ray diffraction (XRD), N2 adsorption/desorption, field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The mechanical properties of the catalysts were studied. The reaction kinetics model of O3 alone and catalytic ozonation of the hydroquinone were established and catalytic ozonation performance of catalysts was investigated. The results showed that the crystal phase of Mn0Co1/CH belonged to CoAl2O4 and that the crystal phase of the Mn-Co/CH catalyst (Mn1Co1, Mn2Co1, and Mn3Co1) mainly belonged to Mn3O4 and CoO. In particular, the Mn1Co1/CH catalyst had a large specific surface area of 190 m2·g-1, high pore volume of 0.25 cm3·g-1, and pore size of 4.8 nm. The highest catalytic activity was obtained when Mn∶Co was 1∶1 (Mn1Co1/CH catalyst). The catalytic activity of the Mn1Co1/CH catalyst was the highest, and removal efficiencies of hydroquinone and COD were 78% and 54%, respectively, using Mn1Co1/CH catalytic ozonation. The Mn-Co/CH catalyst had a high compressive strength (15.89-16.94 MPa). The degradation efficiency of hydroquinone decreased significantly after the addition of tert-butanol, which indicated that·OH played an important role in the Mn1Co1/CH catalytic ozonation. The catalytic ozonation process fitted the first-order kinetic model. The apparent rate constant k for O3 alone was only 0.0306. Furthermore, the Mn1Co1/CH catalyst had the highest rate, with an apparent rate constant k of 0.0535 min-1. The Mn-Co/CH catalyst was easy to industrialize owing to its lower consumption, excellent catalytic characteristics, and long working life.