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Adsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them. [ABSTRACT FROM AUTHOR]

Adsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them. [ABSTRACT FROM AUTHOR]

Three Schiff bases, 2-acetylpyridine thiosemicarbazone ( I), 2-acetylpyridine-(4-methylthiosemicarbazone) ( I), and 2-acetylpyridine-(4-phenylthiosemicarbazone) ( I) were tested against corrosion of cast iron in aqueous solutions of HCl, NaOH, NHCl, and NaCl by means of a mass loss method and electrochemical measurements. The inhibition efficiency is directly proportional to inhibitor concentration, while it decreases with prolonged immersion time and at low temperatures. In order to study the effect of an additive, synergism of KI was also studied. The adsorption of Schiff bases in corrosive media obeys Langmuir's isotherm, both in the presence and absence of KI. The UV-Vis, FT-IR, WAXD and SEM analyses were carried out to support the mechanism of corrosion inhibition. The ΔG values reveal that the inhibition was mainly due to physisorption of the inhibitor molecules on the surface of cast iron. The electrochemical polarization results showed the predominantly cathodic nature of the inhibitors. [ABSTRACT FROM AUTHOR]

The surface properties of a series of imidazoline-based dissymmetric bis-quaternary ammonium (DBA) salts with different hydrophobic chain lengths DBA-12, DBA-14 and DBA-16 were determined. The adsorption behaviors of these compounds in 1 M HCl solution and their inhibitive effect on Q235 steel (U12350) were investigated using the weight-loss method, polarization, and electrochemical impedance spectroscopy. Results indicate that the three inhibitors all showed good inhibition performance for Q235 Steel in 1 M HCl solution and were found to be mixed-type inhibitors. The adsorption behavior of the three inhibitors can fit the Langmuir isotherm equation and the values of $$ \Updelta G_{\text{ads}}^{0} $$ are around or lower than 40 kJ mol, indicating that there is a stronger chemical adsorption. [ABSTRACT FROM AUTHOR]

A study on the removal of hexavalent chromium ions from aqueous solution by using activated carbon prepared from Ricinus communis has been done. In this process, it was carbonised and activated by treating with concentrated sulphuric acid followed by heating for 5 h at 500°C. Batch adsorption experiments are also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data are fitted well to the Freundlich adsorption isotherm. Thermodynamic parameters such as Δ H°, Δ S° and Δ G° are calculated, which indicated that the adsorption is spontaneous and endothermic in nature. Adsorbent used in this study is characterised by FT-IR and SEM before and after the adsorption of Cr(VI). © 2011 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

The adsorption process is gaining interest as an effective process for advanced water and wastewater treatment. Phenol, as a toxic material in industrial effluents, should be removed because of its environmental and health effects. The present study involves an investigation of the use of three carbonaceous materials-activated carbon laboratory-grade (ACL), almond shell charcoal (ASC), and walnut shell charcoal (WSC)-as adsorbents for the removal of phenol from aqueous solutions. For the first time, the adsorptive removal of phenol using ASC and WSC was investigated. Findings have been compared with (ACL) results. Batch experiments were carried out to obtain adsorption equilibrium isotherms with phenol-spiked synthetic solutions. The effects of adsorbent amounts, pH0, initial concentration, and contact time on the adsorption of phenol were studied. Maximum removals of phenol from contaminant water with ACL, ASC, and WSC were 99.87, 91.36, and 78.17%, respectively, and from industrial wastewater were 99.71, 85.54, and 65.49%, respectively. [ABSTRACT FROM AUTHOR]

The frictional behaviors of methyl oleate (MO), methyl palmitate (MP), methyl laurate (ML), and methyl stearate (MSt) as additives in hexadecane have been examined in a boundary lubrication test regime using steel contacts. It was found that the transient attributes of coefficient of friction (COF)-time spectra are a sensitive measure of adsorption equilibria. Critical additive concentrations were defined and used to perform novel and simple Langmuir analyses that provide an order of adsorption energies: MSt > MP > MO > ML. Application of Langmuir, Temkin, and Frumkin-Fowler-Guggenheim adsorption models via nonlinear fitting of a general cooperative model demonstrates the necessary inclusion of cooperative effects in the applied model. In agreement with the qualitative features of steady-state COF-concentration plots, MSt modeling requires minimal cooperative interaction terms. However, MO, MP, and ML data require large attractive interaction terms to be adequately fitted. Primary adsorption energies calculated via the cooperative model are necessarily decreased, whereas total adsorption energies correlate well with values obtained via critical concentration analyses. These results and comparisons with previous adsorption studies of MO and MSt suggest that primary (ester-surface) and secondary (alkyl-surface) adsorbate-adsorbent, adsorbate-adsorbate, and (free-additive) adsorpt-adsorpt interactions collectively determine both the calculated primary and the cooperative interaction energies. [ABSTRACT FROM AUTHOR]