Preferential adsorption of pentachlorophenol from chlorophenols-containing wastewater using N-doped ordered mesoporous carbon

Comparative effect of mesoporous carbon doping on the adsorption of pharmaceutical drugs in water: Theoretical calculations and mechanism study

In this study, mesoporous doped-carbons were synthesized from sucrose, a natural source, boric acid and cyanamide as precursors, generating B- or N-doped carbon. These materials were characterized by FTIR, XRD, TGA, Raman, SEM, TEM, BET, and XPS, confirming the preparation of a tridimensional doped porous structure. B-MPC and N-MPC showed a high surface specific area above 1000 m²/g. The effect of B and N doping on mesoporous carbon was evaluated on the adsorption of emerging pollutants from water. Diclofenac sodium and paracetamol were used in adsorption assays, reaching removal capacities of 78 and 101 mg.g^-1, respectively. Kinetic and isothermal studies indicate the chemical nature of adsorption controlled by external and intraparticle diffusion and multilayer formation due to strong adsorbent/adsorbate interactions. DFT-based calculations and adsorption assays infer that the main attractive forces are hydrogen bonds and Lewis acid-base interactions.

Enhancement of Pb (II) adsorption by boron doped ordered mesoporous carbon: Isotherm and kinetics modeling

Boron doped ordered mesoporous carbon (BMC) was prepared to improve the adsorption of Pb(II). The effects of several parameters such as contact time, pH, and ionic strength on the adsorption by both pristine ordered mesoporous carbon (OMC) and BMC were investigated. Thermodynamic, sorption isotherm and adsorption kinetics models were used to study the adsorption mechanisms by each of the adsorbents. Based on intraparticle diffusion model, the adsorption process by the two adsorbents mainly involved the quick liquid-film diffusion stage and slow pore diffusion portion, and fitting experimental data with Temkin model indicates that the adsorption process by both of the adsorbents involve physisorption and chemisorption. Based on Langmuir model, the estimated maximum adsorption capacity for BMC was about 1.3 times higher than the pristine OMC. Moreover, BMC retained good adsorption performance in tap and lake water, and could be regenerated effectively and recycled using EDTA. The results suggested that BMC, with enhanced adsorption performance compared with OMC, could be considered as very effective and promising materials for Pb (II) removal from wastewater.

Pentachlorophenol removal from aqueous solutions using Montmorillonite modified by Silane & Imidazole: kinetic and isotherm study

BACKGROUND

Removal of pentachlorophenol (PCP) from wastewater containing chlorophenols, due to its toxicity, mutagenic and carcinogenic properties, has been attracted much interests of researchers.

METHODS

In this research, K10 montmorillonite was modified by silane and imidazole (Im) for increasing the removal percentage of PCP from aqueous solutions. It was characterized by FTIR, XRF, FESEM, EDS, and BET techniques. The influence of different parameters such as initial concentration, contact time, adsorbent dosage, pH, temperature and agitating speed was investigated.

RESULTS

The maximum removal percentage (95%) were obtained for PCP at pH = 4. The isotherm experimental data for pentachlorophenol was best fitted using the Langmuir model and the kinetic studies were better described by the pseudo-second-order kinetic model. The thermodynamic study indicated that the adsorption of PCP by the adsorbent was feasible, spontaneous and exothermic.

CONCLUSION

In this study, the modified montmorillonite by silane and imidazole is appropriate and low cost adsorbent for increasing of the removal percentage of PCP from aqueous solutions.

In-situ sampling of chlorophenols in industrial wastewater using diffusive gradients in thin films technique based on mesoporous carbon

In-situ sampling of 2-chlorophenol (CP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP) in industrial wastewater was carried out by the diffusive gradients in thin films (DGT) device based on mesoporous carbon (MC). The diffusion coefficients of CP ((1.33 ± 0.05) × 10^-6 cm² s^-1), DCP((1.35 ± 0.04) × 10^-6 cm² s^-1) and TCP((1.09 ± 0.07) × 10^-6 cm² s^-1)) in nylon membrane at 25 °C were independent of pH 3-9 and ionic strength as pNaCl from 0.155 to 3, and were less than their values in water, demonstrating that the nylon membrane with good tolerance and constant diffusion coefficients was suitable as the DGT diffusion layer for controlling the diffusion of CPs. MC-DGT accurately measured the concentrations of CP, DCP and TCP in synthetic solution (C_DGT/C_SOLN = 0.956-1.04) over the deployment of 120 h. The experimental data also agreed well with the theoretical data calculated on the DGT equation. The performance of MC-DGT for sampling CPs was independent of pH (3-8) and ionic strength as pNaCl (1.3-3) due to the change of the interaction between MC and CPs under relatively high pH and ionic strength. Deployments in laboratory and field trials demonstrated that the MC-DGT was a reliable simple, robust and accurate tool for the in-situ sampling of CP, DCP and TCP in the industrial wastewater.

Influence of alternating current on the adsorption of indigo carmine

The main purpose of this work is to study the effect of a new process of accelerating which consist to couple the electrochemical process with the adsorption to remove an anionic dye, the indigo carmine. That is why, we investigated the effects of the new process of accelerating the adsorption process by using alternating current (AC) on the retention of an anionic dye, the indigo carmine. The adsorption capacity of dye (mg/g) was raised with the raise of current voltage in solution, temperature, and initial indigo carmine concentration and decreased with the increase of initial solution pH, current density, and mass of carbon. The results demonstrate that the removal efficiency of 97.0 % with the current voltage of 15 V is achieved at a current density of 0.014 A/cm², of pH 2 using zinc as electrodes and contact time of 210 min for adsorption in the presence of AC. Concerning the adsorption without AC, the results obtained showed that for an initial concentration equal to 20 mg/L, more than 95 % amount of adsorbed dye was retained after 405 min of contact in batch system. The comparison between adsorption in the presence and absence of an alternating current shows the importance of the alternating current in the acceleration of the adsorption method and improve the performances of FILTRASORB 200. For both cases, the adsorption mechanism follows the fractal kinetics BSf(n,α) model and the Brouers-Sotolongo isotherm model provides a good fit of the experimental data for both adsorption with and without alternating current.

Behaviours of direct yellow 12 adsorption on mesoporous carbons with different pore geometries

Four kinds of mesoporous carbons, C1-h-w, C2-h-h, C3-s-w, and C4-s-h, with different pore geometries were prepared and characterised, and their adsorption behaviours with aqueous direct yellow 12 (DY-12) were investigated. The results of X-ray diffraction and transmission electron microscopy show that C1-h-w and C3-s-w have wormlike pore characteristics, whereas C2-h-h and C4-s-h have 2-D hexagonally arranged pores. According to the N₂ adsorption/desorption results, the specific surface area of C1-h-w (1,378 m²/g) is the largest among the four carbons. The adsorption isotherms could be effectively fitted using the Langmuir model. The maximum adsorption amounts of C1-h-w, C2-h-h, C3-s-w and C4-s-h are 0.968 mmol/g, 0.726 mmol/g, 0.161 mmol/g and 0.156 mmol/g, respectively. The pseudo-second-order rate constants of C1-h-w (39.8 g/(mmol·min)) and C2-h-h (7.28 g/(mmol·min)) are substantially larger than those of C3-s-w (0.0046 g/(mmol·min)) and C4-s-h (0.014 g/(mmol·min)), indicating that an open and interconnected pore geometry is favourable for DY-12 adsorption. Furthermore, DY-12 diffusion in 2-D hexagonally ordered cylindrical pores is superior to that in wormlike pores due to the smoothness of the channels in the former. External mass transfer and intraparticle diffusion both play roles in the adsorption process.

Preparation of magnetic mesoporous carbon from polystyrene-grafted magnetic nanoparticles for rapid extraction of chlorophenols from water samples

A magnetic mesoporous carbon material (Fe₃O₄@C) was fabricated by carbonizing polystyrene grafted polydopamine-coated magnetic nanoparticles.

Sorption of chlorophenols on microporous minerals: mechanism and influence of metal cations, solution pH, and humic acid

Sorption of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) on a range of dealuminated zeolites were investigated to understand the mechanism of their sorption on microporous minerals, while the influence of common metal cations, solution pH, and humic acid was also studied. Sorption of chlorophenols was found to increase with the hydrophobicity of the sorbates and that of the microporous minerals, indicating the important role of hydrophobic interactions, while sorption was also stronger in the micropores of narrower sizes because of greater enhancement of the dispersion interactions. The presence of metal cations could enhance chlorophenol sorption due to the additional electrostatic attraction between metal cations exchanged into the mineral micropores and the chlorophenolates, and this effect was apparent on the mineral sorbent with a high density of surface cations (2.62 sites/nm(2)) in its micropores. Under circum-neutral or acidic conditions, neutral chlorophenol molecules adsorbed into the hydrophobic micropores through displacing the "loosely bound" water molecules, while their sorption was negligible under moderately alkaline conditions due to electrostatic repulsion between the negatively charged zeolite framework and anionic chlorophenolates. The influence of humic acid on sorption of chlorophenols on dealuminated Y zeolites suggests that its molecules did not block the micropores but created a secondary sorption sites by forming a "coating layer" on the external surface of the zeolites. These mechanistic insights could help better understand the interactions of ionizable chlorophenols and metal cations in mineral micropores and guide the selection and design of reusable microporous mineral sorbents for sorptive removal of chlorophenols from aqueous stream.