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Abstract: The treatment of wastes has become one of the most important concerns of modern society to protect the environment. Application of microemulsion modified raw local diatomite (μE-MD) and activated carbon (μE-MAC) as solid extractants for removing inorganic (iron, copper and lead ions) and organic pollutants (soot, oxidations, nitration and sulphation products) from waste lubricants (WL) at a moderate heat have been presented. The results summarised herein are also part of an investigation conducted to evaluate the adsorption removal by taking into consideration the experimental parameters such as initial pollutant concentration and temperature. The raw and modified adsorbents were effective towards all pollutants especially for the inorganic pollutants with high removal percentages (Fe: 34–68%, Cu: ∼65%, Pb: 55–80%) and (oxidation: 7–15%, nitration: 41–46%, sulphation: 5–29%, soot: 42–61%) which indicated the suitability of these new materials for extraction of organic and inorganic pollutants from non-aqueous WL medium. The removal percentages, however, varied from adsorbent to another“. The pHzpc (pH at point of zero charge) was carefully estimated for all adsorbents (raw diatomite (RD), μE-MD, activated carbon (AC), μE-MAC) and found to be (8.6, 7.8, 7.3, 9.1), respectively. The experimental results were also plotted and treated with Langmuir isotherm, uncommon isotherm shapes were obtained. Therefore, it was not fitted to the experimental results which might reflect a complex nature of adsorbing onto the adsorbents. However, this behaviour gave an indication on the complex adsorption mechanisms. Finally, the mode of interaction between the pollutants and the μE-MD and μE-MAC was characterised by comparing the changes in the position and intensity of the surface functional groups using the FTIR technique. Three mechanisms of the adsorption of organic (oxidation, nitration and sulphation) and inorganic (heavy metals) pollutants were possible: (i) adsorption by an electrostatic force of the anionic head group of the surfactant and the positive charge of the organic molecules or the cation metal, (ii) adsorption by tail groups of the surfactant and the hydrophobic character of the organic molecules. The cation heavy metals and the organic compounds have basic characteristics and therefore were expected to interact strongly with the anionic head groups of the surfactants (RCOO−). In the contrary, the cationic heavy metals were not expected to interact by the tail groups of the surfactant where the ionic radii of these ions may explain the differences between every metals removal percentage and (iii) filling the channel (pores) of the RD and the AC by dissolving in the microemulsion micelles. [Copyright &y& Elsevier]

Abstract: The removal of organosulphur compounds (ORS) from diesel fuel is an important aspect of Jordanian''s effort to reduce air pollution by sulphur oxides. The results of this work revealed that activated carbon (AC) has an excellent adsorption for the ORS from non-aqueous diesel medium. Experimental data revealed that percentage removal of the ORS was slightly affected with particle size of the adsorbent, which indicates that elimination of the ORS mainly occurred on the external surface area and the adsorption onto the pores of the adsorbent has a small effect on the entire elimination process. Removal of the ORS by the AC has an endothermic nature where percentage removal values were increased by temperature. The maximum percentage removal value was 72% which was reported at: 2.0g, 300–500μm, 25°C, and 3 days shaking. The experimental results were plotted and treated with Langmuir isotherm, uncommon isotherm shapes were obtained. Therefore, it was not fitted to the experimental results which might reflect a complex nature of adsorbing the ORS onto the AC. However, this behaviour gives an indication on the complex adsorption mechanisms. Finally, the mode of interaction between the ORS and the AC was characterised by comparing the changes in the position and intensity of the surface functional groups using FTIR technique. [Copyright &y& Elsevier]

Abstract: In order to remove the limitations originating from inefficient heat and mass transfer in adsorption refrigeration/heat pump, an innovative arrangement design was proposed. It was equipped with meshed multi-tubular involving activated carbon in a sealed cylindrical adsorber. Related aspects of adsorption refrigeration key parameters were addressed. Working pair, activated carbon–diethyl ether, is used in the above system in order to determine the optimum adsorption refrigeration parameters. In order to estimate the adsorption characteristics and the adsorption capacity of the adsorbent, the adsorption isotherms of that adsorbent, with a specific adsorbate, are carried out. The measured adsorption data were adequately described by the Langmuir equation. The adsorption capacity of the diethyl ether on activated carbon at 26, 35, and 50°C were 0.0159, 0.0220, and 0.0188mmol/g, respectively. Two kinetic adsorption models namely pseudo-first and second order kinetic models were investigated. The thermodynamic parameters, ΔH°, entropy, ΔS°, and Gibbs free energy, ΔG°, of the adsorption process were also obtained from the gas adsorption experiments at various temperatures. These values were −45.84kJ/mol, −88.87J/(molK), and −19.27kJ/mol, respectively. The pseudo-first order model was not applicable in this adsorption system, suggesting that the adsorption process and the rate-limiting step was the pseudo-second order reaction. Therefore, the dominant mechanism might be a chemisorption process between the diethyl ether molecules and the activated carbon surface. The k 2, however, decreased as the initial diethyl ether pressure increased. [Copyright &y& Elsevier]

The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as δ-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the d-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern. [Copyright &y& Elsevier]

The current work presented here focuses on the remediation of mercury from water using modified low-cost materials. Modified date pits, low cost, minimal pretreatment steps and locally abundant agricultural waste materials were effectively employed as an adsorbent for remediating Hg2+ from aqueous media. Physical and chemical modification were developed such as thermal roasting (RDP), sulfur (SMRDP) and silane (SIMRDP) based modifications. Results showed that maximum adsorption by RDP was at pH 6, AC and both modifications was at pH 4. Furthermore, RDP has exothermic adsorption mechanism while AC, SMRDP, and SIMRDP have endothermic. All adsorbents except SIMRDP have spontaneous adsorption process. SEM analysis showed that the surface morphology of RDP was not significantly affected by different treatments while surface of AC was affected. The investigation for good adsorbents for Hg2+ uptake from different anthropogenic sources has been carried out by many investigators worldwide towards having a safe environment. In the current study, the highest Hg2+ adsorption of SMRDP was relatively high compared to other known adsorbents. [ABSTRACT FROM AUTHOR]