The adsorption mechanism of Cr6+ on biochar prepared from corn stalks (raw carbon) was studied by extracting the organic components (OC) and inorganic components (IC). Scanning electron microscopy, ...X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the properties of three kinds of carbon. Kinetic and thermodynamic experiments were performed. The results showed that the experimental data were fitted well by the Freundlich model and the pseudo-second-order kinetic model, and the adsorptions on the three kinds of carbon were all spontaneous, endothermic processes. The adsorption of Cr6+ by biochar was in accordance with a chemisorption process. The adsorption contribution rate of the OC was 97%, which was much higher than that of the IC. Electrostatic attraction and redox reaction were the main mechanisms of adsorption, and among them, the contribution rate of the redox reaction accounted for 61.49%. The reduced Cr3+ could both exchange ions with K+ and dissociate into solution by electrostatic repulsion; the amount of Cr3+ released into the solution was approximately 17.07 mg/g, and the amount of Cr3+ ions exchanged with K+ was 0.29 mg/g. These results further elucidate the adsorption mechanism of Cr6+ by biochar.
Abstract
To remove NO3-N from water, coconut shell biochar (CSB) was modified by a solution of FeCl3, a solution of AlCl3 and a mixture solution of FeCl3 and AlCl3 respectively. The obtained modified ...biochar with the best effect of NO3-N adsorption was screened out to explore the adsorption behavior and mechanism of NO3-N removal by batch experiments and kinetics and thermodynamics and correlated characterization. The results indicated that the mixture solution of FeCl3- and AlCl3- modified CSB (Fe-Al/CSB) showed the best adsorption performance for NO3-N removal. Iron and aluminum elements existed on the surface of Fe-Al/CSB in the form of FeOOH, Fe2O3, Fe2+, and Al2O3 respectively. The adsorption process could reach equilibrium in 20 min. An acidic condition was favorable for NO3-N adsorption. The presence of coexisting anions was not conducive for NO3-N adsorption. The quasi-second-order model and Freundlich model could be well fitted in the adsorption process. The maximum adsorption capacity of Fe-Al/CSB fitted by the Langmuir model could reach 34.20 mg/g. The adsorption of NO3-N by Fe-Al/CSB was an endothermic and spontaneous process. Ligand exchange and chemical redox reaction were the NO3-N adsorption mechanisms which led to NO3-N adsorption by Fe-Al/CSB.
Four deep eutectic solvents (DESs) were synthesized, and 5–30% polyethylenimine (PEI) was added to make functional DESs (FDESs) for dynamic absorption experiments of hydrogen sulfide. The synthesized ...FDESs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance. The results demonstrated the successful synthesis of FDESs. The interaction between H2S and the FDESs was discussed at a molecular level via the quantum chemical calculations. It was noticed that FDESs prefer chemisorption on H2S. In this work, the 25% PEI/FDES@EG showed the highest desulfurization performance. The effects of H2S concentration and temperature on the desulfurization performance were investigated. It was found that a relatively low temperature (30 °C) was favorable for the absorption of H2S. The 25% PEI/FDES@EG could remove H2S efficiently over a low H2S concentration. Moisture played an important role in the FDES desulfurization system. The absorption/desorption cycle experiment indicated that the FDESs retain their good regeneration performance for at least five times.
In this study, the concentrations of seven heavy metals (Cr, Ni, Cu, Zn, As, Hg, and Pb) and Pb isotope in a sediment core from the Shuanglong reservoir, Southwestern China, were investigated. Based ...on the constant rate of supply (CRS) model, the age span of a 60 cm sediment sample was determined to range from the years 1944 to 2015. Combined with chronology and heavy metal content, the evolution of the sources and pollution levels of heavy metals showed a changing trend composed of various stages. The sources of heavy metals transitioned from natural origins in 1944–1964 to industrial origins in 1965–2004. The subsequent reduction in heavy metal content was mainly due to the vigorous implementation of environmental protection policies from 2005 to 2012. In recent years (2013–2015), the heavy metal content has increased due to frequent human activity. Principal component analysis (PCA), correlation analysis, and the coefficient of variation (CV) analysis indicated that Cr, Ni, Cu, Zn, and As were derived from natural processes, Pb mainly came from automobile manufacturing, and Hg was mainly from industrial sources. The values of the geo-accumulation index (Ig), single pollution index (Pi), and single potential ecological risk index (Er) showed that the contamination of Hg and Pb was slight to moderate. Moreover, the values of the potential ecological risk index (RI), pollution load index (PLI), and Nemerow index (PN) indicated that the Shuanglong reservoir is under low ecological risk.
Miniscrew implants (MSIs) have been widely used as temporary anchorage devices in orthodontic clinics. However, one of their major limitations is the relatively high failure rate. We hypothesize that ...a biomimetic calcium phosphate (BioCaP) coating layer on mini-pin implants might be able to accelerate the osseointegration, and can be a carrier for biological agents. A novel mini-pin implant to mimic the MSIs was used. BioCaP (amorphous or crystalline) coatings with or without the presence of bovine serum albumin (BSA) were applied on such implants and inserted in the metaphyseal tibia in rats. The percentage of bone to implant contact (BIC) in histomorphometric analysis was used to evaluate the osteoconductivity of such implants from six different groups (n=6 rats per group): (1) no coating no BSA group, (2) no coating BSA adsorption group, (3) amorphous BioCaP coating group, (4) amorphous BioCaP coating-incorporated BSA group, (5) crystalline BioCaP coating group, and (6) crystalline BioCaP coating-incorporated BSA group. Samples were retrieved 3 days, 1 week, 2 weeks, and 4 weeks post-surgery. The results showed that the crystalline BioCaP coating served as a drug carrier with a sustained release profile. Furthermore, the significant increase in BIC occurred at week 1 in the crystalline coating group, but at week 2 or week 4 in other groups. These findings indicate that the crystalline BioCaP coating can be a promising surface modification to facilitate early osseointegration and increase the success rate of miniscrew implants in orthodontic clinics.
Polymethyl methacrylate is a polymer commonly used in clinical dentistry, including denture bases, occlusal splints and orthodontic retainers.
To augment the polymethyl methacrylate-based dental ...appliances in counteracting dental caries, we designed a polymer blend film composed of polymethyl methacrylate and polyethylene oxide by solution casting and added sodium fluoride.
Polyethylene oxide facilitated the dispersion of sodium fluoride, decreased the surface average roughness, and positively influenced the hydrophilicity of the films. The blend film made of polymethyl methacrylate, polyethylene oxide and NaF with a mass ratio of 10: 1: 0.3 showed sustained release of fluoride ions and acceptable cytotoxicity. Antibacterial activity of all the films to Streptococcus mutans was negligible.
This study demonstrated that the polymer blends of polyethylene oxide and polymethyl methacrylate could realize the relatively steady release of fluoride ions with high biocompatibility. This strategy has promising potential to endow dental appliances with anti-cariogenicity.
The adsorption mechanisms of mercury ion (Hg2+) by different fractions of biochar were studied, providing a theoretical basis and practical value for the use of biochar to remediate mercury ...contamination in water. Biochar (RC) was prepared using corn straw as the raw material. It was then fractionated, resulting in inorganic carbon (IC), organic carbon (OC), hydroxyl-blocked carbon (BHC), and carboxyl-blocked carbon (BCC). Before and after Hg2+ adsorption, the biochar fractions were characterized by several techniques, such as energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Obtained results indicate that the reaction mechanisms of RC for Hg2+ removal mainly include electrostatic adsorption, ion exchange, reduction, precipitation, and complexation. The equilibrium adsorption capacity of RC for Hg2+ is 75.56 mg/g, and the adsorption contribution rates of IC and OC are approximately 22.4% and 77.6%, respectively. Despite the lower rate, IC shows the largest adsorption capacity, of 92.63 mg/g. This is attributed to all the mechanisms involved in Hg2+ adsorption by IC, with ion exchange being the main reaction mechanism (accounting for 39.8%). The main adsorption mechanism of OC is the complexation of carboxyl and hydroxyl groups with Hg2+, accounting for 71.6% of the total OC contribution. BHC and BCC adsorb mercury mainly via the reduction–adsorption mechanism, accounting for 54.6% and 54.5%, respectively. Among all the adsorption mechanisms, the complexation reaction of carboxyl and hydroxyl groups with Hg2+ is the dominant effect.
Inorganic salts prohibit seriously the biological treatment of the wastewater discharged from the production of long-chained dicarboxylic acids from liquid paraffin by microbial fermentation. First, ...the inorganic salts in wastewater were removed partly by means of neutralization–precipitation. Second, the neutralized wastewater was treated in an anaerobic baffled reactor (ABR) and a sequencing batch reactor (SBR). The digested sludge from the sewage treatment plant was taken as the seed sludge for ABR and the returned sludge for SBR, respectively. After adding glucose and rice-washing water as carbon sources, a sludge free of salt to degrade organic pollutants was cultivated. The sludge samples were observed through fluorescence microscope. It was found that the microorganisms in the SBR sludge are mainly zoogloea with a small quantity of infusorians, while the microorganisms in the ABR sludge are mainly filamentous bacteria and bacillus. More than 90% COD in the wastewater can be removed after the treatment by the neutralization–precipitation combined with ABR-SBR technique.
► A combined technique was used to treat the hypersaline wastewater. ► After treated, the COD removal rate of the wastewater can reach more than 90%. ► The influences of HRT, OLR, pH, temperature on COD removal rate were investigated. ► The results may have implications in studies on wastewater with high salt.
The H2S removal performances of four deep eutectic solvent (DES) based nanofluid (NF) systems were measured using dynamic absorption experiment. The Cu containing NF system is found to be an ...excellent absorbent for H2S removal with a significantly enhanced desulfurization performance compared with DES original solution. Besides, the NF systems have relatively high regeneration performance. The NF systems and Cu nanoparticles before and after absorption as well as after regeneration were characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive spectrum (EDS). It is found that the ethanolamine, choline cation and sulfur were accumulated on the surface of Cu nanoparticles after absorption, and the bulk elements on the surface were identified as Cu and S after regeneration. The S−2 was existed in the form of Cu2S, and some sulfur was oxidized to zero-valent sulfur after regeneration.
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•Nanofluid systems based on nonaqueous solution were used for H2S removal.•The H2S removal performance was enhanced after the introduction of Cu nanoparticles.•The desulfurization rate increased due to the interaction of Cu and ethanolamine.•The nanofluid systems showed relatively high regeneration performance.•Sulfur was accumulated on the surface of Cu in the form of Cu2S and S(0).
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•In the absence of strain, its energy band value is the largest. Under compress, its energy band value decreases slowly, but under stretch, its energy band value decreases to metallic ...properties.•The formation of the heterojunction can change the light performance very well. Under the visible light, the adsorption efficiency is greatly increased.•Under different strain, the charge density and the charge density difference change with the variation of the strain.
Strain modulation is one of the most popular tuning methods for the electronic properties of low-dimensional systems. In the present work, by using first principles study, strain engineering is used to module the band gap transition of two novel van der Waals (vdW) heterostructures based on two-dimensional (2D) Blue P (Blue Phosphorene) supported on MoSe2, producing Blue P-MoSe2 systems. The Blue P-MoSe2 vdW heterostructures could withstand 8% of the applied tensile strain. The electronic structure of the Blue P-MoSe2 vdW heterostructures could be changed effectively under the tensile force. The band gap changed from direct to indirect under the strain and could be tuned in the range of 0.075–1.284 eV. At approximately −4% of the applied strain, there was a transition of the valence band maximum (VBM). A wider range of light absorption could be obtained under the strain. Furthermore, MoSe2 acts as an electron-donating layer in the Blue P-MoSe2 vdW heterostructure, and the potential drop across the interface can generate a large built-in electric field across the interface; this electric field plays a crucial role in preventing the recombination of photogenerated charges. Our results provide a prospect for the future applications of two-dimensional materials in electronic and optoelectronic devices.
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