Silica nanoparticles loaded on activated carbon for simultaneous removal of dichloromethane, trichloromethane, and carbon tetrachloride

Characterization and use of activated carbon synthesized from sunflower seed shell in the removal of Pb(II), Cd(II), and Cr(III) ions from aqueous solution

In this work, carbon-based nanomaterials such as active carbon which is prepared from common sunflower (Helianthus annuus) seed shell, and the characterization of the activated carbon NPs were studied using FTIR (Fourier transform infrared spectroscopy), XRD, SEM, EDS, and DTA techniques. Activated carbon NPs have been used in the adsorption of Pb(II), Cd(II), and Cr(III) ions from the aqueous phase. The results showed the highest adsorption efficiency was 99.9%, 92.45%, and 98% for Pb(II), Cd(II), and Cr(III) ions respectively at a temperature of 25 °C, pH = 7-9, and a time of 60 and 180 min, in addition to the accordance of the adsorption models for activated carbon with the Freundlich isotherm model at the value of R2 (0.9976, 0.9756, and 0.9907) and Langmuir isotherm model (0.966, 0.999, and 0.9873) of the Pb(II), Cd(II), and Cr(III) ions, respectively. We conclude the possibility of using activated carbon to have an extremely high sorption capacity across the conditions tested, with the highest adsorption efficiency having been >99% for Pb(II), Cd(II), and Cr(III) ions within the pH range 7-9 and a contact time of 60 to 180 min.

Highly Selective Chloromethanes Detection Based on Quartz Crystal Microbalance Gas Sensors with Ba-MOFs

Three new metal-organic frameworks (MOFs), {(CH₃NH₃)₃[Ba₂(TTHA)(NO₃)(H₂O)₂]}·2H₂O (1), {(CH₃NH₃)₄[Ba₃(HTTHA)₂(H₂O)₇]}·3H₂O (2), and [Ba₇(TTHA)₂(NO₃)₂(H₂O)₁₀]·2H₂O (3) (H₆TTHA = 1,3,5-triazine-2,4,6-triamineh-exaacetic acid) have been synthesized and characterized. The sensing properties of 1-3 were explored with regard to volatile organic compounds (VOCs) by the quartz crystal microbalance (QCM) technique. The results indicated that 1 and 2 have a much higher selectivity and response to chloromethanes (CH₂Cl₂, CHCl₃, and CCl₄) compared with H₂O, CH₃OH, CH₃CH₂OH, CH₃CN, (CH₃)₂CO, C₆H₆, C₆H₅CH₃, C₆H₅CH₂CH₃, and C₆H₅Cl at room temperature. Furthermore, 1 and 2 sensing film also exhibits excellent reversibility and stability, and the response and recovery times are almost within 10 s. 3 displays a lower response and poor selectivity to the above VOCs. The significant difference may be caused by their different structural characteristics. The Ba²⁺ ions are all decacoordinated in 1 and 2, while Ba²⁺ ions have more open metal sites in 3. So, the high selectivity and response of 1 and 2 may be due to the exchange of coordination water molecules with chloromethanes and possible electrostatic effects between (CH₃NH₃)⁺ cations and chloromethanes containing more electronegative Cl atoms. DFT calculation results show that the bond energy of Ba-Cl and Ba-O is not much different, so chloromethanes at high concentrations may exchange coordination water to form weak Ba···Cl interactions and show higher response values. 3 has no obvious VOCs selectivity and higher response due to more open sites of Ba²⁺ ions and smaller pore size. This work develops a fast and effective method to detect chloromethanes, providing a new opportunity for designing QCM gas sensors coated with different MOF materials.

Exhaustive valorization of cashew nut shell waste as a potential bioresource material

In this paper, we report extraction of cashew nut shell liquid (CNSL) from cashew nut shell waste (CNSW) and further use of residues for generation of activated carbon for removal of heavy metals and methylene blue (MB). Solvent extraction yielded 24.6 ± 0.4%, 38.2 ± 0.4% and 40.1 ± 0.9% for petroleum ether, hexane and ethanol respectively. Phytochemical screening showed presence of alkaloids, carbohydrates, saponins, phenols, tannins, flavonoids, amino acids, terpenoids, proteins, steroids, glycosides and carboxylic acids. The CNSL had a pH of 3.2, viscosity (104.6 ± 1.8 mPa s), moisture (6.5%), ash (1.6 ± 0.1%), refractive index (1.52 ± 0.001), specific density (0.9561 ± 0.0002 g/cm³), acid value (118.7 ± 9.2 mg KOH/g), free fatty acid value (60.1 ± 4.7%), saponification number (138.1 ± 3.2 mg KOH/g) and iodine value (188.1 ± 2.3 mgI 2/100 g). The average percentage removal of Cu (II), Pb (II), Cd (II) and Zn (II) was 99.4 ± 0.5, 95.4 ± 1.5, 99.5 ± 0.1, 98.4 ± 0.1%, and removal efficiency of MB at 50, 150, 250 and 350 mg/L was 99.63, 97.66, 96.48 and 94.81%, respectively. Equilibrium data were best described by the Freundlich isotherm model. The maximum monolayer adsorption capacity was 12.1 mg/g. The adsorption kinetics conformed to pseudo-second-order model. ∆G° was negative and a ∆H° of + 22.76 kJ/mol indicated that adsorption was endothermic. The ΔS° (+ 0.086 kJ/mol/K) showed that there was spontaneous interaction of the solution and adsorbate. These results show that CNSW is a potential bioresource for CNSL production for use in the paints, varnishes, surface coatings, agrochemicals and ethnomedicine industries. Residual shells can be exploited as fuels or converted to activated carbon for use as low-cost filters in water purification.