Preparation of Activated Carbon From Olive Stone Waste: Optimization Study on the Removal of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from Aqueous Solution Using Response Surface Methodology

The removal efficiencies of Cu²⁺, Cd²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ from aqueous solution with olive stone activated carbon (OSAC) were investigated in this paper. Central composite design method was used to optimize the preparation of OSAC by chemical activation using potassium hydroxide (KOH) as chemical agent. The optimum conditions obtained were 715°C activation temperature, 2 hours activation time, and 1.53 impregnation ratio. This resulted in removal of 99.25% Cu²⁺, 94.98% Cd²⁺, 99.08% Ni²⁺, 99.33% Pb²⁺, 99.41% Fe²⁺, and 99.17% Zn²⁺, as well as 73.94% OSAC yield. The surface characteristics of the activated carbon (AC) prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer–Emmett–Teller (BET) surface area, total pore volume, and average pore diameter of the prepared activated carbon were 886.72 m²/g, 0.507 cm³/g, and 4.22 nm, respectively. The equilibrium data of the adsorption was well fitted to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Fe²⁺ (57.47 mg/g), followed by Pb²⁺ (22.37 mg/g), Cu²⁺ (17.83 mg/g), Zn²⁺ (11.14 mg/g), Ni²⁺ (8.42 mg/g), and Cd²⁺ (7.80 mg/g). The prepared OSAC can be used for efficient removal of metals from contaminated wastewater.     

Sol–gel synthesis of mesoporous silicas containing albumin and guanidine polymers and its application to the bilirubin adsorption

The organic–inorganic composite materials based on mesoporous silica were synthesized using sol–gel method. The surface area of silicas was modified by bovine serum albumin (BSA) and guanidine polymers: polyacrylate guanidine (PAG) and polymethacrylate guanidine. The mesoporous silicas were characterized by nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy, transmission electron microscopy. The obtained materials were used as adsorbents for selective bilirubin removal. It was shown that the structural properties and surface area of modified materials depend on the nature of polymers. Incorporation of polymers in silica gel matrix during sol–gel process leads to the formation of mesoporous structure with high pore diameter and a BET surface area equals to 346 m²/g for SiO₂/BSA and 160 m²/g for SiO₂/PAG. Analysis of adsorption isotherms showed that modification of silica by BSA and guanidine polymers increases its adsorption ability to bilirubin molecules. According to Langmuir model, the maximum bilirubin adsorption capacity was 1.18 mg/g.     

Thermal stabilities of hexagonal and orthorhombic YbFeO3 synthesized by solvothermal method and their catalytic activities for methane combustion

Thermal stabilities of hexagonal and orthorhombic YbFeO₃ samples synthesized by the solvothermal method were investigated. The morphology and BET surface area of hexagonal YbFeO₃ did not change by calcination, while orthorhombic YbFeO₃ easily sintered, resulting in a decrease of the BET surface area. The hexagonal YbFeO₃ sample, which had a high surface area (29 m²/g) after calcination at 800 °C, had higher catalytic activity for methane combustion than the orthorhombic YbFeO₃ samples calcined at 800 °C.     

Surface and Structural Properties of Gold Nanoparticles and Their Biofunctionalized Derivatives in Aqueous Electrolytes Solution

Gold nanoparticles reduced by sodium citrate (d ～ 10 nm) and purchased gold colloid particles (d ～ 500 nm) were examined and compared. The properties of both gold particles and their biofunctionalized derivatives with L-cysteine and L-glutathione were studied in the presence of sodium nitrate. The structural investigations indicated an aggregated inner structure.

The isoelectric points of pure gold, citrate reduced gold, and functionalized gold were measured and compared. The low isoelectric point of pure gold/water interface was explained by considering the distribution and accumulation of H⁺ and OH^? ions within the interfacial water layer, being more pronounced for OH^? ions.      

Separation and Extraction of Uranium from Leach Liquor Containing Uranium and Molybdenum by Solvent Extraction with LIX 622N

The leach liquor (0.5 g/L Mo, 0.05 g/L U) obtained from the leaching process of molybdenum-uranium ore material was treated using solvent extraction to recover U(VI) by LIX 622N, which is a salicylaldoxime derivative. The influence of various basic variables such as pH, concentration of LIX 622N, temperature, different stripping reagents, phase ratio, and diluents was examined. Using 10% LIX 622N with the aqueous solution of equilibrium pH 6.0 and a phase ratio organic phase:aqueous phase (O:A) = 1:1, a two-stage McCabe-Thiele plot was constructed, which showed 99.9% of U extraction with no co-extraction of molybdenum. This was confirmed by a 6-cycle counter current simulation (CCS) study. The obtained data of temperature on the extraction of uranium showed that the extraction process is exothermic with enthalpy change of ?20.949 kJ mol^?1. The stripping of U(VI) was quantitative using 4 M H₂SO₄. The stable complex UO₂(HSO₄)R_org formed during extraction, which supports the cation exchange mechanism, and was confirmed by FTIR spectral analysis.      

Rheological Properties of SiC Suspensions with a Compound Surface Modification Using Ethyl Orthosilicate and Ethylene Glycol

Ultrafine silicon carbide (SiC) powders were surface-modified using ethyl orthosilicate (TEOS) combined with ethylene glycol. SiC suspensions with favorable rheological properties, low viscosity, and high solid loading were successfully obtained. The mechanisms of the compound surface modification for SiC powders as well as the influences of the compound surface modification not only on functional groups and charge state of the surface for SiC powders but also on the rheological properties of SiC suspensions were investigated in the present study. The results show that under alkaline conditions and acidic conditions, the surface charge states of SiC powders were [Si-OCH₂CH₂O]^? and [Si-OCH₂CH₂OH₂]⁺, respectively. The absolute value of zeta potential reached the maximum value of 22.69 mV at pH 11. Additionally, with added 1 wt% TEOS and 3 wt% ethylene glycol, the SiC suspensions exhibited good rheological properties, low viscosity and high stability due to the steric hindrance and electrostatic repulsion offered by the [Si-OCH₂CH₂O]^- with a high concentration.     

Mesoporous activated carbon from <Emphasis Type="Italic">Pentace</Emphasis> species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer–Emmett–Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418 W, radiation time of 6.4 min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15 m²/g, 0.52 cm³/g, and 3.19 nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich–Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Sips equations. However, the exponential value of Redlich–Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14 mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.     

Synthesis and Aqueous Solution Properties of Polyoxyethylene Surfactants with Ultra-Long Unsaturated Hydrophobic Chains

Methoxypolyethylene glycols (M _n = 750, 1000, 2000, and 5000 g/mol) were hydrophobically modified by transestification with mono-unsaturated alkyl chains (UC18, UC22, and UC24), and the obtained ultra-long-chain nonionic surfactants were characterized by ¹H NMR, FTIR and gel permeation chromatographic, respectively. Aqueous solution properties of all these surfactants, including cloud point, surface activities, viscosifying ability, and phase diagrams were examined. It was found that all these ultra-long-chain polyoxyethylene surfactants exhibit good water solubility and typical Newtonian rheological behavior. For the surfactants with the same hydrophobic length, the CP, equilibrium surface tension (γ_cmc), as well as zero-shear viscosity (η₀) increase with increasing their hydrophilic length; for those with same hydrophilic head group, the critical micellar concentration and η₀ increase while the γ_CMC decreases with increasing hydrophobic tail length. Moreover, a decrease in the critical overlap concentration and an increase in the critical temperature were observed in phase diagrams of all these ultra-long-chain polyoxyethylene surfactants. (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)