Mild Hydrothermal Synthesis of 11Å-TA from Alumina Extracted Coal Fly Ash and Its Application in Water Adsorption of Heavy Metal Ions (Cu(II) and Pb(II))

Non-biodegradable copper (Cu) and lead (Pb) contaminants in water are highly toxic and have series adverse effects. Therefore, it is very important to extract heavy metals from wastewater before it is discharged into the environment. Adsorption is a cost-effective alternative method for wastewater treatment. Choosing a low-cost adsorbent can help reduce the cost of adsorption. In this study, conversion of reside after extracting aluminum (REA) produced by sub-molten salt method transform high-alumina coal fly ash (CFA) into 11Å-tobermorite to adsorb Cu(II) and Pb(II) from aqueous solutions at room temperature. The synthesis of the adsorbent was confirmed using scanning electron microscope (SEM), X-ray diffractometer (XRD) and Brunauer–Emmett–Teller (BET) method surface analysis. To study the adsorption characteristics, factors such as initial Cu(II) and Pb(II) concentration, pH, contact time, adsorption characteristics and temperature were investigated in batch mode. The maximum adsorption capacity of Cu(II) and Pb(II) was 177.1 mg·g−1 and 176.2 mg·g−1, respectively. The Langmuir adsorption model was employed to better describe the isothermal adsorption behavior and confirm the monolayer adsorption phenomenon. The pseudo-second-order kinetic model was used to highlight Cu(II) and Pb(II) adsorption kinetics. Thermodynamic analysis indicated the removal Cu(II) and Pb(II) by TA-adsorbent was a nonspontaneous and exothermic reaction. The obtained results are of great significance to the conversion of industrial waste to low-cost adsorbent for Cu(II) and Pb(II) removal from water.

Gas Adsorption and Storage at Metal-Organic Frameworks

Dry gas is considered one of the most environmentally friendly sources of energy. As a result, developing an efficient strategy for storing this gas has become essential. In this work, MOF-199 was synthesized and characterized in order to investigate the MOF-199 in dry gas adsorption using a built-in volumetric system (methane, ethane, and propane from Basrah gas company). The MOF-199 (metal organic framework) was synthesized using the solvothermal method at 373K for 24h, and then it was characterized. The dry gas adsorption on MOF-199 was studied under various conditions (adsorbent dosage, contact time, temperature, and pressure). The isothermal adsorption of the dry gas had been studied on MOF-199 using two types of models: Freundlich and Langmuir. The results of the isothermal adsorption shown corresponded to the Freundlich model with a correlation coefficient (R²) of 0.9426. Also, the rate of adsorption kinetic of the first and second-order was studied, and the results showed that the reaction rate was second-order.

Thiol-Functionalization Carbonaceous Adsorbents for the Removal of Methyl-Mercury from Water in the ppb Levels

Mercury is a highly toxic pollutant of major public health concern, and human exposure is mainly related to the aqueous phase, where its dominant form is methyl-mercury (MeHg). In the current work, two carbon-based adsorbents, i.e., a commercial activated carbon and a sunflower seeds’ biochar, were modified by the introduction of thiol-active groups onto their surfaces for the MeHg removal from natural-like water in ppb concentration levels. The examined thiol-functionalization was a two-step process, since the raw materials were initially treated with nitric acid (6 N), which is a reagent that favors the formation of surface carboxyl groups, and subsequently by the thiol surface bonding groups through an esterification reaction in methanol matrix. The adsorbents’ capacity was evaluated toward the Hgtotal legislative regulation limit (1 μg/L) in drinking water (denoted as Q1). The respective isothermal adsorption results revealed an increased affinity between MeHg and thiol-functionalized materials, where the commercial carbon showed slightly higher capacity (0.116 μg Hg/mg) compared with the biochar (0.108 μg Hg/mg). This variation can be attributed to the respective higher surface area, resulting, also, to higher thiol groups loading. Regarding the proposed mechanism, it was proved that the S-Hg bond was formed, based on the characterization of the best performed saturated adsorbent.

The performance of calcined serpentine to simultaneously remove fluoride, iron and manganese

To solve the problem of high fluoride, iron and manganese concentrations in groundwater, serpentine (Srp) was modified by metal salt impregnation, acid-base activation and calcination, and the effects of these three modifications on removal performance of Srp were compared. Specifically, the effects of the calcined serpentine (Csrp) dose, reaction time, pH, and temperature on the removal performance of F−, Fe2+ and Mn2+ on Csrp were analysed. An isothermal adsorption model and adsorption kinetic equation were established and confirmed through SEM, EDS, XRD and FTIR spectroscopy to analyse the mechanism of removing F−, Fe2+ and Mn2+ by Csrp. The results show that when 3 g/L Csrp was used to treat water samples with 5 mg/L F−, 20 mg/L Fe2+, and 5 mg/L Mn2+ (pH of 6, reaction temperature of 35 °C, and time of 150 min), the removal rates of F−, Fe2+, and Mn2+ were 94.3%, 99.0%, 98.9%, respectively. The adsorption of F−, Fe2+ and Mn2+ on Csrp follows the quasi-second-order kinetic equation and Langmuir isotherm adsorption model. After 5 cycles of regeneration of Csrp, Csrp can still maintain good properties of fluoride,iron and manganese removal.

Mechanism of Oxytetracycline Removal by Coconut Shell Biochar Loaded with Nano-Zero-Valent Iron

In this paper, coconut shell biochar (BC), pickling biochar (HBC), and nano-zero-valent iron-loaded biochar (nZVI-HBC) were prepared; these were used to remove oxytetracycline (OTC), and the removal mechanism and degradation product were analyzed. These biochars were characterized using SEM, XRD, FTIR, and XPS. The effects of biochar addition amount, pH, ion type, and ion concentration on OTC adsorption were studied by a batch adsorption experiment. Under the optimal conditions, the equilibrium adsorption capacity of nZVI-HBC to OTC was 196.70 mg·g−1. The adsorption process can be described by Langmuir isothermal adsorption equations, conforming to the pseudo-second-order dynamics model, indicating that adsorption is dominated by single-molecule chemical adsorption, and a spontaneous process of increasing heat absorption entropy. Mass spectrometry showed that the OTC removal process of nZVI-HBC included not only adsorption but also degradation. These results provide a practical and potentially valuable material for the removal of OTC.

Molecular Simulation of the Adsorption Characteristics of Methane in Pores of Coal with Different Metamorphic Degrees

In order to study differences in the methane adsorption characteristics of coal pores of different metamorphic degrees, 4 nm pore structure models based on three typical coal structure models with different metamorphic degrees were constructed. Based on the molecular mechanics and dynamics theory, the adsorption characteristics of methane in different coal rank pores were simulated by the grand canonical Monte Carlo (GCMC) and molecular dynamics methods. The isothermal adsorption curve, Van der Waals energy, concentration distribution, and diffusion coefficient of methane under different conditions were analyzed and calculated. The results showed that at the same pore size, the adsorption capacity of CH4 is positively correlated with pressure and metamorphic degree of coal, and the adsorption capacity of CH4 in high metamorphic coal is more affected by temperature. The relative concentration of CH4 in high-order coal pores is low, and the relative concentration at higher temperature and pressure conditions is high. The CH4 diffusion coefficient in high-rank coal is low, corresponding to the strong Van der Waals interaction between CH4 and coal. The research results are of great significance for further exploration of the interaction mechanism between CH4 and coal with different metamorphic degrees and can provide theoretical support for the selection of gas extraction parameters.

Synthesis of C,N,S-tridoped TiO2 distribute onto silicone for photocatalytic on degradation of tetracycline under visible light irradiation

Using carbon, nitrogen, and sulfur sourced from thiourea to co-doped TiO2 (C,N,S-TiO2), was prepared via hydrothermal method using precursors of titanyl sulfate TiOSO4, obtained by decomposition of ilmenite ore in Binh Dinh. The material used to make the substrate is glass and distributed onto it is silicone and photocatalytic. The structure and properties of materials system were investigated by modern physicochemical analysis methods including scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, diffuse reflection spectroscopy UV-Vis, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and nitrogen isothermal adsorption. The photocatalytic ability of materials system after being carried by silicone is demonstrated by decomposing tetracycline (10 mg/L) in aqueous solution with the yield more than 88% efficiency after 6 hours under visible light irradiation. The optimum dose of the photocatalyst was 0.6 g/L under visible light irradiation. The results indicated that C, N, S co-doped TiO2 demonstrated the highest photocatalytic efficiency and a perspective recyclable potential when it is distributed onto silicone.

Determination of Phthalate Esters in Beverages and Water Samples by Solid Phase Extraction with Resin Based COFs as Filler

Resin based covalent organic framework material was used as filler for solid phase extraction (SPE), and the solid phase extraction effect was compared with that of traditional COF material (TpBD COFs). The enrichment capacity of four phthalate esters (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate) in beverage samples was investigated by SPE. Adsorption experiments showed that the kinetic adsorption behavior of COF materials for phthalate esters (PAEs) was more consistent with the quasi-second-order kinetic adsorption model, and the static adsorption behavior is more in line with the Freundlich isothermal adsorption model. Solid phase extraction experiments proved that the SPE column prepared with two COF materials as adsorbents had good adsorption effects, high recovery (water: 97.99–100.56% and beverage: 97.93–100.23%) and were reusable (50 cycles), which could meet the requirements for trace detection of phthalate ester. It was found that the solid phase extraction effect was better than the four types of commercial SPE columns. The new COF material reduced the cost of monomer use and provided the possibility for its industrial production. Meanwhile, it also provided a new feasible scheme for enriching trace phthalate esters in practical samples.

Cr(VI) Adsorption from Aqueous Solution by UiO-66 Modified Corncob

To adsorb hexavalent chromium (Cr(VI)) in polluted water, this paper prepared a UiO-66 (Zr6O4(OH)4(BDC)12) modified granular corncob composite adsorbent by hydrothermal method with in situ loading of UiO-66 on pretreated corncob particles. The physicochemical properties of the synthesized samples were characterized. Batch adsorption experiments were conducted to investigate the adsorption process of aqueous Cr(VI) under various conditions (different ionic strength, pH and co-existing anions). The results showed that UiO-66 was successfully loaded on the modified corncob particles. The isothermal adsorption data of Cr(VI) adsorption by the UiO-66 modified corncob fit well with the Langmuir model with the maximum adsorption capacity of Cr(VI) on UiO-66@Corn+ being 90.04 mg/g. UiO-66 loading could increase Cr(VI) adsorption capacity of Corn+. The kinetic study showed that the equilibrium time for Cr(VI) adsorption on UiO-66 modified corncob was about 180 min and the kinetic data followed the pseudo-secondary kinetic model. The Cr(VI) adsorption capacity on UiO-66@Corn+ decreased with the increasing solution pH, and the optimum pH range was 4–6. The ionic strength has little effect on the Cr(VI) adsorption capacity, but the coexistence of CO32−, SO42− and PO43− in the solution could significantly decrease the equilibrium adsorption capacity of Cr(VI). The adsorption mechanism analysis showed that Cr(VI) was adsorbed on the surface of adsorbents through electrostatic attraction and was reduced further to the less toxic Cr(III) by the electron donor on the surface of adsorbent. The electrostatic interaction was the main force affecting the adsorption of Cr(VI) by UiO-66. UiO-66@Corn+ had an excellent removal efficiency of Cr(VI) and excellent reusability. UiO-66@Corn+ could effectively remove Cr(VI) from water and have a promising application.