In view of the fugitive dusts caused by wind disturbance and material handling in coal bunkers, surface plants, and open-air coal stocking yards of coal businesses, the solidifying dust suppressant based on modified chitosan is synthesized and prepared through the chemical modification of –NH2 with chitosan as a raw material and –NH2 was replaced by –CH2CH(OH)CH2N+(CH3)CI− through the technique of Fourier transform infrared spectroscopy. According to viscosity experiment results, the viscosity of the modified solidifying dust suppressant increased significantly. The coal particles suppressed by the dust suppressant as observed with a 50,000X scanning electron microscope were coagulated together, which indicated very good cohesion effect. In addition, wind erosion resistance experiment was conducted to analyze the wind erosion rate of coal powders before and after sprayed with the suppressant at different wind speeds, which indicated that the dust suppressant can effectively prevent fugitive dusts at a wind speed of 17 m/s.
The definition of a nanofiber is discussed, and the history of the development of bubble electrospinning is briefly elucidated, its main properties are emphasized, and the morphology of its products is summarized. A geometrical interpretation of the nanofiber membrane's adsorption is given as a natural intrinsic property of the geometrical potential of nanoscale structure. Nano-effect, Casimir effect, capillary effect, Earth's gravity difference, Newton's gravity, and lotus leaf's highly selective repulsion property can all be interpreted using the geometrical potential or boundary-induced force.
Activated carbons (ACs) were synthesized from golden shower (GS) through chemical activation. Two synthesis processes were used: one-stage and two-stage processes. In the one-stage process, GS that was impregnated with K2CO3 was directly pyrolyzed (GSAC), and the two-stage process consisted of (1) pyrolytic or hydrolytic carbonization to produce biochar or hydrochar and (2) subsequent chemical activation was defined as GSBAC and GSHAC, respectively. The activated carbon’s characteristics—thermal stability and textural, physicochemical, structural, and crystal properties—were thoroughly investigated. Results demonstrated that the characteristics of activated carbons strongly depend on the method used for their synthesis. The Brunauer–Emmett–Teller surface area followed the order GSAC (1413 m2/g) > GSHAC (1238 m2/g) > GSBAC (812 m2/g). The existence of acidic groups was determined through Fourier transform infrared spectroscopy and Boehm titration. The excellent adsorptive capacities of the activated carbons were confirmed from the iodine number (1568–2695 mg/g) and methylene number (143–233 mg/g).
Hydrogel nanocomposites were synthesized by solution polymerization of acrylic acid in the presence of sodium alginate biopolymer and TiO2 nanoparticle. TiO2 nanoparticle and N,N-methylene-bis-acrylamide was used as an inorganic and organic crosslinker, respectively. The structure and morphology of the nanocomposites were investigated using X-Ray Diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and thermogravimetric analysis techniques. The nanocomposites hydrogel was used for the adsorption of methyl violet dye from water. The influence of TiO2 nanoparticle, sodium alginate content and grafting on adsorption were studied. The results showed that a pseudo-second-order adsorption kinetic was predominant in the adsorption of methyl violet onto the nanocomposite hydrogel. The experimental equilibrated adsorption capacity of the nanocomposite hydrogel agrees with Langmuir isotherm. Maximum adsorption capacity of 1156.61 mg g−1 and adsorption efficiency of 99.6% towards methyl violet were obtained for the hydrogel nanocomposite.
We report here a reliable green method for the synthesis of palladium nanoparticles supported on copper oxide as a highly active and efficient catalyst for Suzuki cross-coupling reaction. The experimental synthetic approach is based on microwave-assisted chemical reduction of an aqueous mixture of palladium and copper salt simultaneously using hydrazine hydrate as reducing agent. The catalyst was fully characterized using various techniques showing well-dispersed palladium nanoparticles. The catalytic activity and recyclability of the prepared catalyst were experimentally explored in the ligand-free Suzuki cross-coupling reaction with a diverse series of functionalized substrates. The synthesized Pd/CuO catalyst shows many advantages beside its high catalytic efficiency such as the recyclability of up to five times with negligible loss of catalytic activity, short reaction times, use of environmentally benign solvent systems, and mild reaction conditions.
This paper proposes the development of a novel coagulant for dust suppression in open-cast mines. Specifically, pretreated sodium lignin sulfonate and acrylic acid were first cross-linked, then the graft copolymerization of the intermediate product (the cross-linking product) and acrylamide was conducted and finally the resulting gelatinous substances were crushed. During the reaction process, N,N’-methylene-bis-acrylamide and ammonium persulfate were used as the cross-linking agent and initiator, respectively. Subsequently, the functional groups, crystalline structure, and thermal stability of the dust coagulant were examined by means of Fourier transform infrared spectra measurements, X-ray diffraction spectra measurements, and differential scanning calorimeter analysis. Moreover, single-factor experiments were conducted to explore the optimal synthesis condition. According to the experimental results, the coagulant achieved its optimal dust suppression performance under the following conditions: the mass ratio of lignin to acrylic acid was 1:3, the mass ratio of lignin to acrylamide was 2:7, the content of the cross-linking agent was 0.9%, the mass ratio of initiator to acrylamide was 2:100, the reaction temperature was set as 60℃, and the pH value was set as 7. Finally, the coagulant was measured for its swelling kinetics, viscosity, film-forming hardness, peeling strength, and ability to suppress dust. It can be concluded that the coagulant exhibits a very high standard of both dust suppression and wind resistance.
In the present work, a new low-cost activated carbon was prepared from paper mill sludge in order to remove Cr(VI) ions from aqueous solution. The effects of adsorbent dosage, pH, contact time, metal ion concentrations, and temperature on adsorption efficiency were studied by experimental tests. The maximum equilibrium uptake of Cr(VI) by the adsorbent was 23.18 mg g−1 at optimum pH = 4.0, contact time of 180 min, and temperature of 45℃. Analysis of equilibrium adsorption data in terms of several isotherm models revealed that Langmuir isotherm with respect to Freundlich isotherm indicates better agreement with the experimental data. The kinetics of Cr(VI) adsorption onto activated carbon was described with the pseudo-second-order model which indicates the dominance of chemisorption mechanism. Thermodynamic parameters indicated that the Cr(VI) adsorption onto adsorbent was feasible in nature, spontaneous, and endothermic.
Two novel adsorbents derived from shrimp shell were prepared and their adsorption performances on Congo red were investigated. The results suggested that treated shrimp shell powder exhibited a higher adsorption capacity than raw shrimp shell powder. The factors of initial concentration, solution pH, adsorption time, and temperature were investigated. The maximum adsorption capacity of treated shrimp shell powder calculated according to the Langmuir isotherm model was 288.2 mg/g, which is much higher than that of chitin. The adsorption behavior could be fitted well by the pseudo-second-order kinetic model. Intra-particle diffusion model was also used to study the adsorption process. The thermodynamic parameters indicated the spontaneous and endothermic nature of the adsorption. Shrimp shell powder exhibited enough advantages such as large adsorption capacity, low cost, simple processing methods and high specific gravity compared with chitin or chitosan. This work confirmed that the shrimp shell biosorbent had a potential to be applied in dye wastewater treatment area.
The use of bottom ash of expired drugs incineration for removal of Cu(II) ions from aqueous solution has been investigated. Analytical techniques have been employed to find characteristics of adsorbent materials. The removal of Cu(II) was conducted in batch system, and the effects of pH, adsorbent dosage, initial concentrations of copper ions, and contact time on adsorption efficiency were studied. Optimum adsorption was achieved at a pH 5 and equilibrium was established within 15 min of the process. The equilibrium adsorption data were analyzed using eight adsorption isotherm models: Langmuir, Freundlich, Temkin, Redlich–Peterson, Dubinin–Radushkevich, Toth, Harkin–Jura and Halsey isotherms. The energy value obtained by application of Dubinin–Radushkevich model was 2.593 kJ/mol indicating that physisorption was the dominant mechanism of sorption. The values of the correlation coefficient (R2) of the isotherms gave the best fit (>0.99) with the Langmuir, Toth, and Redlich–Peterson isotherms. The adsorption capacity (qm) from the Langmuir isotherm for Cu(II) was found as 13.335 mg/g. The equation constant n of Toth isotherm model is found to be close to 1 (0.945), confirming that the adsorbent studied presents homogeneous surface under conditions used. It is concluded that bottom ash of expired drugs incineration can be used as an effective adsorbent for removing Cu(II) from aqueous solution.
In aqueous solutions, hexavalent chromium Cr(VI) was successfully removed by activated carbon “Z. jujuba rubidium carbonate-activated carbon” obtained from waste lignocellulosic material (Ziziphus jujuba cores). Rubidium carbonate was used to prepare Z. jujuba rubidium carbonate-activated carbon by chemical activation using a 1:1 w/w ratio. Our results indicate that the obtained surface area of the activated carbon was equal to 608.31 m2/g. The adsorption study of Cr(VI) was investigated under batch conditions at constant stirring speed (220 r/min). Factors such as pH (1–6), temperature (20–40°C), adsorbent concentration (0.5–3 g/l), and initial Cr(VI) concentration (50–500 mg/l) were all studied to attain the maximum removal efficiency. Prior to the adsorption process, the morphology, elementary composition, and loss mass of activated carbon were characterized using scanning electron microscopy, X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Fourier transform infrared analysis of the adsorbent demonstrated the presence of key functional groups associated with the adsorption phenomenon such as those of hydroxyl and aromatic groups. The obtained results showed that the optimal conditions for a maximum adsorption efficiency are 2 for pH, 1 g/l for activated carbon dosage and 100 mg/l for Cr(VI) concentration. The removal percentage increased from 27.2 to 62.08%. The kinetic sorption was described by a pseudo-second-order kinetic equation (R2 ≈ 0.995). The Tóth (R2 = 0.997) and Elovich models were best to explain the sorption phenomenon. Thermodynamic studies showed that the adsorption of Cr(VI) onto activated carbon was feasible, spontaneous, and endothermic at 20–40°C. This novel Z. jujuba rubidium carbonate-activated carbon derived from Z. jujuba core has been found to be effective for the removal of Cr(VI) and not harmful to the ecosystem.
Biodegradable and efficient filtration membrane is essential to practical oil–water separation. Herein, we fabricated highly porous membrane induced by the humidity. The resulting poly(lactic acid) fiber membrane exhibits superhydrophobicity due to more trapped air by the increased roughness of fiber at the relative humidity of 80%. Meanwhile, the increased humidity favors to the membrane porosity improvement from 81 ± 3.3% to 92 ± 4.1% with the humidity change from 40% to 80%. The superhydrophobicity company with the increased membrane porosity makes the functional poly(lactic acid) membrane with enhanced flux for practical oil–water separation.
In the present article, the optimization of removal of Cu2+, Ni (2+), and Pb (2+) using sugarcane-based activated carbon was studied. The activated carbon synthesized from low-cost sugarcane bagasse via ZnCl2 activation process was found to possess surprisingly high surface area (> 1500m(2)/g). In adsorption study, the individual and interactive effects of three critical parameters including initial concentration, pH of solution, and activated carbon dosage on removal efficiency of Cu2+, Ni2+, and Pb2+ were assessed by applying the response surface methodology combined with central composite design. The established second-order polynomial regression models provided an excellent interpretation of experimental data with acceptable coefficients of determination (R-2) and analysis of variance demonstrated statistical significance of the model terms. In the examined region, the predicted maximum removal efficiency and adsorption capacity were found in the order: Ni2+ (66.4%, 2.99 mg/g)< Cu2+ (90%, 13.24 mg/g)< Pb2+ (99.9%, 19.3 mg/g), which were also confirmed in the verification experiments.
A novel, cheap, less toxic, and easier-prepared gelatin surfactant is successfully used as corrosion inhibitor for the corrosion of copper in 0.1 M H2SO4 at the temperature range: 25–55°C. The critical micelle concentration of the surfactant was determined from surface tension measurements. The inhibition efficiency was determined from potentiodynamic polarization and electrochemical impedance spectroscopy techniques. For surfactant acted by adsorption at copper/solution interface, an inhibition efficiency up to 68 was obtained at critical micelle concentration (70 ppm) of surfactant at 35°C. The free energy of adsorption was calculated and discussed. The surface parameters of gelatin surfactant were calculated and correlated to the inhibition efficiency. They were also calculated from its surface tension profile including: critical micelle concentration), maximum surface excess (Γmax), and minimum surface area (Amin). The thermodynamic of micellization, free energies of micellization (ΔGmic) and entropy of micellization, was calculated and discussed. The formation of compact and adherent monomolecular adsorbed film on copper substrate was confirmed.
The calcium silicate hydrate synthesized from electrolytic manganese residue was investigated as adsorbents to remove the phosphate from aqueous solutions. The effects of different experimental parameters, including contact time, initial phosphate concentration, solution pH, and temperature on the phosphate adsorption were investigated. The results showed that the phosphate adsorption was highly pH-dependent, with removal being more efficient under the pH range of 10.0–11.0. The Freundlich and Langmuir models were used to simulate the sorption equilibrium, and the results indicate that the adsorption data fitted well to the Langmuir model with which the maximum phosphate adsorption capacity was estimated to be 65.79–85.47 mg/g at 25–35°C. Meanwhile, the kinetic data confirmed that the sorption of phosphorus onto electrolytic manganese residue–calcium silicate hydrate can be best described by the pseudo-second-order kinetic model, suggesting that the adsorption process might be chemical sorption. Furthermore, thermodynamic studies illustrated that the adsorption process was endothermic and spontaneous in nature.
Nowadays, phenol and chlorophenols give rise to many organic pollutants. Concurrently, the occurring of phenolic compounds in aquatic ambit creates potential human health and environmental problems. There are a lot of technologies available for the treatment of organic pollutants. To remove phenol and chlorophenols, adsorption is a wastewater purification method. In this study, natural and activated clinoptilolite were carried out for the removal of phenol, ortho-chlorophenol, para-chlorophenol, and meta-chlorophenol. Activated clinoptilolite was prepared via acid activation and evaluated by means of Fourier transform infrared, scanning electron microscope, X-ray diffraction, X-ray fluorescence, and Brunauer–Emmett–Teller analysis. Phenol and chlorophenols have high adsorption rate, and equilibrium was reached in approximately 30 min. The maximum adsorptions of phenol, ortho-chlorophenol, meta-chlorophenol, and para-chlorophenols on the activated clinoptilolite were 6.7386, 8.6300, 9.5787, and 7.3758 mg g−1, respectively. The affinity order was in the following order: m-CP > o-CP > p-CP > Ph. The adsorption of phenol and chlorophenols decreased after pH = 6.25. Using the thermodynamic data, Gibbs free energy of the activated clinoptilolite was evaluated. The effects of different conditions such as pH, adsorption time, and initial concentration were analyzed. The adsorption rates of phenol and chlorophenols were constituted to be the maximum at approximately pH 6.5. Desorption of phenol and chlorophenols was carried out using ethyl alcohol solution (30%, v/v). The adsorption isotherms of phenol and chlorophenols on activated clinoptilolite were evaluated. The equilibrium adsorption data were the best suited to Freundlich adsorption isotherm pattern.
The isosteric heat of adsorption (IHA) is one of the key thermodynamic variables for evaluating the interaction between shale and methane, which is rarely studied especially under high pressure. In this work, we conducted methane adsorption experiments at pressures up to 30 MPa and different temperatures on shale samples collected from Longmaxi formation in Sichuan Basin, China. Based on the definition of IHA and Langmuir adsorption model, we proposed a new method to analyze the IHA of methane on shale under four conditions. The calculated results show that the commonly used Clausius–Clapeyron equation overestimates the true isosteric heat of shale, especially under high pressure. IHA under four conditions yield a fixed order as qst,i-va > qst,r-va > qst,i+va > qst,r+va, indicating both the real gas behavior and the adsorbed-phase volume have a negative influence on it, and the effect of adsorbed-phase volume is dominant. Moreover, IHA at zero coverage ( qst0) in Henry region determined by linear fitting can be regarded as a maximum value in the above four cases, which is independent of pressure and temperature. Therefore, qst0 can be used as a unique descriptor to evaluate the adsorption affinity of the shale. This work modified the method to obtain the true IHA of supercritical methane on shale more accurately, which lays the foundation for future investigations of the thermodynamics and heat transfer characteristics of the interaction between high pressure methane and shale.
The capacity and underlying mechanism of hydrochars derived from commercial D-glucose and wasted orange peels (designated as pristine-hydrochars) and further modified with nitric acid (designated as oxidized-hydrochars) to adsorb methylene blue were investigated. Both pristine- and oxidized-hydrochars were characterized by scanning electron microscopy, Brunauer–Emmet–Teller-specific surface area, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and mass titration. The maximum methylene blue adsorption capacity at 30°C estimated by the Langmuir model was found to follow the order: mGH (246 mg/g) > mOPH (107 mg/g) > OPH (59.6 mg/g) > GH (54.8 mg/g). Six adsorption mechanisms were elucidated, in which the electrostatic interaction and hydrogen bonding were identified as the primary methylene blue-hydrochar adsorptive interaction; furthermore, because the nitric acid modification process enhanced oxygen- and nitrogen-containing functional groups and unsaturated bonds on the surface of oxidized-hydrochars, the π–π and n–π interaction became minor pathways for methylene blue adsorption onto oxidized-hydrochars. Our results suggest that modified hydrochars could be used as environmentally friendly adsorbents alternative to activated carbon in dealing with methylene blue contamination in aqueous solutions.
The occurrence of coal and gas outbursts is closely linked to the presence of tectonic coal. To study the pore structure characteristics and adsorption characteristics of different destruction types of coal, nondestructive coal, destructive coal, strongly destructive coal, pulverized coal, and fully pulverized coal are selected based on the coal and gas outburst mine identification specifications. The experimental methods used are liquid nitrogen adsorption, mercury intrusion porosimetry and CH4 isothermal adsorption. The results show that the pore volume obtained by the Barrett–Joyner–Halenda method and the specific surface area increase with increasing destruction type. For all tested coal samples, the N2 adsorption/desorption hysteresis loop is not closed when the relative pressure is low, indicating the existence of ink-bottle pores, an elastic structure of the coal and nitrogen affinity in the coal. With increasing tectonic stress, it becomes more advantageous to produce micropores. The pore volume obtained by the mercury intrusion porosimetry experiment increases with increasing destruction types except for the case of fully pulverized coal. High-pressure mercury causes pore deformation and collapse. When the f value is <0.5, the compression effect of the pores is obvious. The smaller the value of f is, the wider is the pore range affected by the high-pressure mercury. The degree of destruction is positively correlated with the porosity, specific surface area, and Langmuir volume. However, the degree of destruction is negatively correlated with the f value and mercury extrusion efficiency.
The quantitative kinetic and equilibrium adsorption parameters for chlorure de méthylrosaniline (gentian violet, crystal violet) removed by commercial activated carbon were studied by UV–visible spectroscopy.Activated carbon with a high specific surface area 1250 m2/g was characterized by the Brunauer, Emmett et Teller (BET) method and the zero charge point pH (pzc). The adsorption properties of both activated carbon with gentian violet were conducted at variable stirring speed 100–700 trs/min, adsorbent dose 1–8 g/l, solution pH 1–14, initial gentian violet concentration 5–15 mg/l, contact time 0–50 min, and temperature 299–323 K using batch mode operation to find the optimal conditions for a maximum adsorption. The adsorption mechanism of gentian violet was studied using the pseudo-first-order, pseudo-second-order, and Elovich kinetic models. The adsorption kinetics was found to follow a pseudo-second-order kinetic model with a determination coefficient (R2) of 0.999. The Weber–Morris diffusion model was applied for the adsorption mechanism. The equilibrium adsorption data of gentian violet were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation (qmax = 22.727, 32.258 mg/g at 26 and 40°C, respectively). The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters, i.e. free energy (ΔG° = − 2.30 to −5.34 kJ/mol), enthalpy (ΔH° = 36.966 kJ/mol), entropy (ΔS° = 0.131 kJ/mol K), and activation energy (Ea) 40.208 kJ/mol of gentian violet adsorption. The negative ΔG° and positive ΔH° indicate that the overall adsorption is spontaneous and endothermic in nature.