Search

This research focused on the effect of particle size and flotation time on magnesite flotation, and the flotation performance of various size fractions were predicted by a machine learning (ML) method. Four kinetic models were used to fit the recovery of MgO and SiO2 in various size fractions of magnesite flotation. The results demonstrated that the flotation of magnesite exhibits good agreement with the classical first-order kinetic model. Besides, the effect of various particle sizes on MgO recovery and selectivity index was predicted by ML method. It was shown that the proposed ML model could accurately reproduce the effects of particle size and flotation time on magnesite flotation performance. Furthermore, the developed model revealed that the optimal mean size range for magnesite flotation is 30 to 48 μm. Therefore, this paper is of great significance to the application of ML methods in the prediction of various magnesite size flotation performance.

Curcumin has received considerable interest in functional food areas due to its variety of biological effects. However, its utilization is often limited by its insolubility and instability in aqueous solutions. Herein, curcumin was encapsulated in γ-cyclodextrin metal–organic frameworks (CD-MOFs) to achieve immediate release and rapid dissolution in water just by gentle stirring due to the dissociation of CD-MOFs. The released curcumin exhibited remarkably enhanced stability compared to its free form in aqueous solutions due to the inclusion effects of cyclodextrins. Besides, the impacts of temperature, light and gastrointestinal pH on the chemical stability of curcumin released from basic and neutral CD-MOFs were compared. The molar ratios of curcumin : γ-CD in basic CD-MOFs and neutral CD-MOFs were 1 : 1.7 and 1 : 9.8, respectively. Neutral CD-MOFs were more effective in retarding thermal and gastrointestinal degradation of curcumin because all curcumin molecules can form inclusion complexes with cyclodextrin. Basic CD-MOFs were more conducive to prolonging the half-life time of curcumin during photodegradation since its alkalinity darkened the color of curcumin solution causing lower light transmittance. Moreover, CD-MOFs exhibited higher loading and stability of curcumin due to their unique host–guest structure, than their pure cyclodextrin inclusion complex. Curcumin-loaded CD-MOFs having a fast-dissolving ability accompanied by the improved amorphous form stability of curcumin hold great potential as functional additives in instant food.

In this paper, the effect of sodium butyl xanthate (NaBX) adsorption on the surface of bornite at different pH on flotation was studied by adsorption kinetic and thermodynamic. The flotation results demonstrated that the recovery was the highest when pH was 9 in NaBX solution (4×10−5 mol/L). The adsorption kinetics showed the reaction of NaBX on the bornite conformed to the second order kinetic equation; it belonged to the multimolecular layer adsorption of Freundlich model; the maximum adsorption rate constant was 0.30 g/(10−6 mol·min), and the equilibrium adsorption capacity was 2.70×10−6 mol/g. Thermodynamic calculation results indicated that the adsorption process was spontaneous chemisorption, and the adsorption products of NaBX on bornite surface were cupric butyl xanthate, ferric butyl xanthate and dixanthogen, which were confirmed by infrared spectrum measurements.

Hydrolysis has been commercially practiced for isolating hemicelluloses from wood chips. Acidification has also been reported as means to isolate lignocelluloses from hydrolysate. However, the performance of hydrolysis and subsequently acidification of induced hydrolysate on non-wood species is unclear. In this work, the hot water hydrolysis of wheat straw, rice straw and maize straw and the acidification of the generated hydrolysates were investigated. The hot water hydrolysis process of wheat, rice and maize straws were optimized. The effect of acidification on separating lignin from hydrolysates was also evaluated as a means to generate lignin. The properties of the collected lignocelluloses were determined to identify a potential application for them. The optimal conditions of the hydrolysis for straws were liquid/solid ratio of 12/1 (wt/wt), temperature of 170 °C and time of 60 min, which yielded rice straw hydrolysate containing more sugars than did the hydrolysates of wheat and maize straws. Acidification to pH 1.5 led to 27.49%, 29.17% and 23.38% lignin removals from the hydrolysates of wheat, rice and maize straws, respectively. Acidification decreased the furfural concentration of hydrolysates and increased the acetic acid concentration. The precipitates generated via acidification of hydrolysates had different heating values, thermal stability and ash content, and the precipitates of acidified rice straw hydrolysate had a higher heating value and thermal stability, but lower ash, than did those of acidified wheat and maize straws. The hot water hydrolysis of different straws could be conducted under the same conditions, but the acidification of hydrolysates would generate lignin with varied properties that may be suitable for altered applications. These results provide evidence for the impact of straw type on the thermal properties of extracted lignin of straw and thus its potential applications.

Herein, we present a transition-metal free direct O-arylation of arylhydroxylamines employing diaryliodonium salts as arylation reagents to form transient N,O-diarylhydroxylamines that could subsequently undergo [3,3]-sigmatropic rearrangement and re-aromatization to afford structurally diverse NOBIN analogs in good to excellent yields under mild conditions.

We have synthesised two kinds of graphitic carbon nitride (g-C3N4) through a pyrolysis process involving urea and melamine. The obtained products were characterised by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflection spectroscopy, and nitrogen adsorption–desorption. The product derived from the urea shows a mesoporous honeycomb-like nanosheet structure (denoted by h-g-C3N4): compared with the bulk product obtained from melamine (denoted by b-g-C3N4), the h-g-C3N4 showed better adsorption and higher photo-activity for rhodamine B (RhB) reduction. The h-g-C3N4 also shows good reusability after cyclic adsorption–regeneration. The present results evinced an efficient design, an eco-friendly and convenient photocatalyst, and a tunable photo-reactivity for use in sustainable light-to-energy conversion.

Chemithermo-mechanical pulp (CTMP) has been widely utilized in papermaking industry because of its high yield. However, the poor strength properties arising from the high contents of hemicellulose and lignin have limited its applications. In this study, ultrasonicassisted cold caustic extraction (CCE) on hemicellulose removal was applied to ascertain its influence on the properties of CTMP. It was found to have a positive effect on hemicellulose removal and resultant pulp properties. At the same alkali concentration (3 wt%), hemicellulose removal and Canadian Standard Freeness (CSF) in ultrasonic-assisted CCE (360 W, 10 min) increased 53.4% and 9.6%, respectively. Ultrasonic-assisted CCE reduces alkali concentration from 5 wt% to 2 wt% to obtain similar hemicelluloses removal, whereas the pulp yield at 2 wt% NaOH was higher than that of CCE alone at 5 wt% NaOH. In addition, at the same alkali concentration (3 wt%), the tensile index, bursting index and tearing index of CTMP in ultrasonic-assisted CCE (120 W, 10 min) increased by 12.7%, 11.34% and 3.0%, respectively. Ultrasonic-assisted CCE enhanced the fibrillation of fibers at optimal conditions, as determined by SEM.

In this study, the hydrogenotrophic denitrifying bacterium Ochrobactrum anthropi was added in to the process of nitrate removal by starch-stabilized nanoscale zero valent iron (nZVI) to minimize undesirable ammonium. The ammonium control performance and cooperative mechanism of this combined process were investigated, and batch experiments were conducted to discuss the effects of starch-stabilized nZVI dose, biomass, and pH on nitrate reduction and ammonium control of this system. The combined system achieved satisfactory performance because the anaerobic iron corrosion process generates H2, which is used as an electron donor for the autohydrogenotrophic bacterium Ochrobactrum anthropi to achieve the autohydrogenotrophic denitrification process converting nitrate to N2. When starch-stabilized nZVI dose was increased from 0.5 to 2.0 g/L, nitrate reduction rate gradually increased, and ammonium yield also increased from 9.40 to 60.51 mg/L. Nitrate removal rate gradually decreased and ammonium yield decreased from 14.93 to 2.61 mg/L with initial OD600 increasing from 0.015 to 0.080. The abiotic Fe0 reduction process played a key role in nitrate removal in an acidic environment and generated large amounts of ammonium. Meanwhile, the nitrate removal rate decreased and ammonium yield also reduced in an alkaline environment.

Controllable degradation is important for the biodegradable polymers used as drug carriers, because the drug release rate can be regulated by the degradation rate. Here, we synthesized chitosan-graft-poly(D, L-lactic acid) copolymers (CgPCs) with high MSPDLLA (molar substitution of poly(D, L-lactic acid)), which possessed controllable biodegradability for regulating the drug release rate. CgPCs with high MSPDLLA were prepared efficiently through an eco-friendly system of 1-ethy-3-methyimidazolium acetate (EmimAc)/4-Dimethylaminopyridine (DMAP). The MSPDLLA reached the maximum of 12.00 within 5 hours, which involved 2.91 of DSPDLLA (the degree of substitution of poly(D, L-lactic acid)) and 4.13 of DPPDLLA (the degree of polymerization of poly(D, L-lactic acid)). Importantly, the biodegradation rate of CgPCs could be regulated by the MSPDLLA. CgPCs with MSPDLLA of 3.98 showed good hydrophilicity and fast degradation leading to burst release of curcumin, whereas CgPCs with MSPDLLA of 12.00 exhibited relatively poor hydrophilicity and slower degradation resulting in sustained release of curcumin. This study provides some new possibilities for controllable biodegradation of drug carriers and optionality of burst or sustained drug release.

The adhesion behavior between particles in the pulp will seriously affect the index of concentrate. In this paper, the effect of citric acid on chlorite in hematite reverse flotation system was studied. The flotation test and settlement test of artificial mixed ore showed that a lower dosage of citric acid could significantly improve the removal rate of chlorite. The mineral contact angle measurement and zeta potential analysis, combined with the extended DLVO theory showed that chlorite is easily adsorbed on the surface of hematite, results in a lower removal rate, and the phenomenon was analyzed by a laser particle size analyzer and optical microscope. The results showed that citric acid can reduce the apparent grain size of artificial mixed ore and improve the dispersion degree of pulp by changing the wettability and surface potential of the minerals, thus increased the removal rate of chlorite.