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Atrazine and glyphosate are two of the most used pesticides around the world causing serious water contamination. In this study, amine-functionalized Santa Barbara Amorphous-15 silica (SBA-15-NH2) was synthesized and employed for the aqueous adsorption of atrazine and glyphosate. The adsorbent was mesoporous post-functionalization with lower surface area, pore volume, size, and stability when compared to the SBA-15. The pesticides adsorption rates were high with over 85% of potential adsorption having occurred within the initial 180 min. The equilibria for atrazine and glyphosate adsorption were 60 and 360 min, respectively, and the rate data fit the fractal pseudo-second-order and pseudo-second-order models, respectively. Atrazine adsorption was higher at lower solution pH with reduced adsorption as the pH value increased. There was enhanced atrazine adsorption as temperature increased from 22 to 32 °C, but further temperature rise resulted in lower adsorption compared to that recorded at 22 °C. The processes comprise electrostatic interaction, trapping of atrazine within mesopores, and multi-layer adsorption of atrazine on surface-adsorbed atrazine. The equilibrium data fitted the Langmuir adsorption isotherm model better than the Freundlich. The SBA-15-NH2 adsorption capacity for atrazine and glyphosate was better than many adsorbents reported in literature, the adsorbent is reusable, and exhibited sustained efficiencies for atrazine that was ≥82% even after 3-cycles, an indication of chemical stability and renewability. [ABSTRACT FROM AUTHOR]

Domestic, agricultural, and industrial waste has been investigated as a substitute for activated carbon adsorbents. For instance, the transformation of tea waste to biochar can be utilized as a substitute for activated carbon adsorbents. In this study, tea waste-based biochar adsorbents (biochar, biochar/reduced graphene oxide (biochar/rGO), biochar/reduced graphene oxide/deep eutectic solvent-cetyltrimethylammonium bromide (biochar/rGO/DES-CTAB), and biochar/reduced graphene oxide/deep eutectic solvent-glycerol (biochar/rGO/DES-glycerol)) were synthesized by simple thermal treatment of tea waste and sucrose followed by modification with reduced graphene oxide and deep eutectic solvents. The obtained materials were characterized using a range of spectroscopy techniques, Fourier Transformed Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy–Energy-Dispersive X-ray Spectroscopy (SEM–EDS), Brunauer, Emmett, and Teller (BET) surface area analysis, and pH at point of zero charge (pH PZC). The obtained results showed that the principal material, i.e., biochar was modified, and FTIR results confirmed the presence of added functional groups. SEM images revealed surface structural changes, and BET showed a decrease in pore size from 10.16 nm to 6.87 nm. The synthesized materials were applied for the removal of ZDV and phenol from the aqueous medium. Batch adsorption studies were conducted to optimize operating parameters such as the adsorbent dose, solution pH, contact time, and initial concentration. Pseudo-first-order (PFO), Pseudo-second-order (PSO), and intraparticle diffusion (IPD) kinetic models were determined to investigate the mechanism of the adsorption process. The coefficient of correlation, R2, was used to determine the best fit of the kinetic models. The adsorption results showed that the DES-glycerol-modified adsorbent was more efficient in removing the pollutants ZDV and phenol than biochar, biochar/rGO, and biochar/rGO/DES-CTAB adsorbents. In addition, the results showed that an acidic medium of pH 2.00 and a contact time of 1 h 30 min and 30 min is sufficient for removing ZDV and phenol, respectively, from an aqueous medium. [ABSTRACT FROM AUTHOR]

The adsorption of sulfamethoxazole (SMZ) and ketoprofen (KET) using carbon nanotubes (CNTs) and CNTs modified with ionic liquids (ILs) was investigated. Two ionic liquids (1-benzyl, 3-hexyl imidazolium, IL1 and 1-benzyl, 3-decahexyl imidazolium, IL2) were synthesized, and characterized by nuclear magnetic resonance ( 1 H and 13 C NMR) and high resolution-mass spectrometry (HR-MS). CNTs and modified CNTs were characterized using FT-IR, X-ray diffraction (XRD), surface area and porosity analysis, thermal gravimetric analysis (TGA), Zeta potential, Raman and scanning electron microscopy (SEM). Kinetics, isotherm and computational studies were carried out to determine the efficiency and adsorption mechanism of SMZ and KET on modified CNTs. A density functional theory (DFT) method was applied to shed more light on the interactions between the pharmaceutical compounds and the adsorbents at the molecular level. The effects of adsorbent dosage, concentration, solution pH, energetics and contact time of SMZ and KET on the adsorption process were investigated. The adsorption of SMZ and KET on CNTs and modified CNTs were pH dependent, and adsorption was best described by pseudo-second-order kinetics and the Freundlich adsorption isotherm. Ionic liquid modified CNTs showed improved adsorption capacities compared to the unmodified ones for both SMZ and KET, which is in line with the computational results showing performance order; CNT+KET/SMZ < CNT–ILs+SMZ < CNT–ILs+KET. [ABSTRACT FROM AUTHOR]