Fawzi Banat

Removal of iron from industrial lean methyldiethanolamine (MDEA) solvent by adsorption on sepiolite

ABSTRACT Sepiolite clay was used as an adsorbent for the removal of iron ions from industrial methyldiethanolamine (MDEA) solvent. The raw sepiolite clay was modified by different chemical and thermal treatments, and was characterized by FTIR, XRD, SEM-EDX, and BET-specific surface area analysis. Treating sepiolite with nitric acid significantly improved the adsorption capacity of iron ions from lean MDEA. The experimental equilibrium data were represented by Henry, Freundlich, and Langmuir isotherm models. The thermodynamic parameters indicated that the adsorption of iron ions on sepiolite was spontaneous and endothermic process. The kinetic studies showed that the adsorption followed pseudo-second order model.

Sunlight-Induced photochemical synthesis of Au nanodots on α-Fe 2 O 3 @Reduced graphene oxide nanocomposite and their enhanced heterogeneous catalytic properties

In this present study, we report the synthesis of Au nanodots on α-Fe2O3@reduced graphene oxide (RGO) based hetero-photocatalytic nanohybrids through a chlorophyll mediated photochemical synthesis. In this process, chlorophyll induces a rapid reduction (30u2009min) of Au3+ ions to Au° metallic nanodots on α-Fe2O3@RGO surface under sunlight irradiation. The nucleation growth process, photo-induced electron-transfer mechanism and physico-chemical properties of the Au@α-Fe2O3@RGO ternary nanocomposites were systematically studied with various analytical techniques. This novel photochemical synthesis process is a cost-effective, convenient, surfactant-less, and scalable method. Moreover, the prepared ternary nanocomposites enhanced catalytic activity as compared to pure α-Fe2O3 and α-Fe2O3@RGO. The advantages and synergistic effect of Au@α-Fe2O3@RGO exhibit, (i) a broader range of visible-light absorption due to visible light band gap of α-Fe2O3, (ii) lower recombination possibility of photo-generated electrons and holes due to effect of Au and (iii) faster electron transfer due to higher conductivity of RGO. Therefore, the prepared Au@α-Fe2O3@RGO hetero-photocatalytic nanohybrids exhibited a remarkable photocatalytic activity, thus enabling potential active hetero-photocatalyst for industrial and environmental applications.

Prediction of foaming and surface tension of lean MDEA solutions with corrosion inhibitor (bis(2-hydroxyethyl)cocoalkylamine) in continuous foam fractionation column

ABSTRACT Amine foaming is a common problem in gas sweetening unit. Prediction of foaming behavior will help in unraveling the operational challenges faced by the gas industry. This study was performed with the aim of predicting the foam volume and surface tension of lean methyldiethanolamine solutions in presence of bis(2-hydroxyethyl)cocoalkylamine (BHCL) corrosion inhibitor using continuous foam fractionation technique. The effect of BHCL as a model foam creators on foaming tendency was explored. The obtained experimental results were used to determine the empirical parameters k and n of the power law relation previously derived for high viscous fluid (i.e., ), both and are dimensionless parameters. The prediction model gave a good agreement with the experimentally observed results (<6% deviation). The foam height model helped in envisaging the surface tension profile and in turn the separation performance and efficiency of foam creators. The foam height increased with increasing superficial gas velocity and BHCL concentration. For low BHCL concentrations, the minimum surface tension was noticed at superficial gas velocity of 0.02u2009m/s.

Removal of sulfide from aqueous solutions using novel alginate–iron oxide magnetic hydrogel composites

Magnetic hydrogel composite beads were prepared by impregnating iron oxide nanoparticles (NP) into macroporous calcium alginate gel (Alg) and used as an adsorbent (Alg/iron oxide-NP) for the removal of sulfide from aqueous solutions. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopic analyses were performed to characterize the iron oxide nanoparticles and the Alg/iron oxide-NP for exploring the mechanism involved in sulfide removal. The experimental results showed that adsorption of sulfide on Alg/iron oxide-NP beads reached equilibrium within 3xa0h. At pH 7.5 and 25xa0°C, Alg/iron oxide-NP was capable of reducing sulfide concentration from 64.3 to 1.1xa0mg/L, thus achieving more than 98% removal. The removal of sulfide decreased with the increase in solution ionic strength. The equilibrium isotherm studies obeyed Langmuir model better than Freundlich model. The maximum uptake capacity was found to be 136.9xa0mg/g. Pseudo-second-order model described the kinetics of sulfide adsorption having rate constant 0.004xa0gxa0mg−1xa0min−1. The proposed mechanism and the experimental data evidenced that chemical interaction was involved in adsorption wherein elemental sulfur and sulfates were produced as byproducts. The adsorbent was regenerated with calcium chloride solution. In five adsorption–desorption cycles, the adsorbent lost less than 5% of its removal efficiency. The magnetic property of the iron oxide nanoparticles enabled easy and rapid separation of the adsorbent from the solution via magnetic field. The synthesized magnetic composite had comparable if not superior adsorption capacity in comparison with carbon-based adsorbents.

Enhanced removal of methyl violet 6B cationic dye from aqueous solutions using calcium alginate hydrogel grafted with poly (styrene-co-maleic anhydride)

Calcium alginate hydrogel was grafted with poly (styrene-co-maleic anhydride) synthetic polymer (PSMA) and used as an adsorbent for the effective removal of methyl violet 6B cationic dye from aqueous solutions. The characteristics of native and grafted alginate hydrogels were investigated using FTIR, Zetasizer and TGA/DSC. The carboxyl groups’ content and the swelling properties were determined as well. Batch adsorption experiments were conducted as a function of initial dye concentration, adsorbent dosage, solution ionic strength, solution pH, time of contact and temperature. Results revealed that grafting of PSMA onto alginate improved the removal percentage of the dye up to 30%. The highest adsorption capacity of the dye was obtained at a temperature of 40xa0°C, a pH range of 5–11 and at lower solution ionic strengths. The kinetics of adsorption followed the pseudo-second-order model and the equilibrium data could be better described by the Langmuir isotherm. The maximum adsorption capacity was found to be 109.9xa0mg/g suggesting the promising potential of our low-cost adsorbent for the removal of cationic dyes from aqueous solutions. A desorption study was carried out where the adsorbent showed high desorption characteristics and it could be reused at least for five consecutive cycles.

Calcium alginate gel and hard beads for the removal of total organic acid anions and heavy metal ions from industrial lean methyldiethanolamine solvent

Bio-polymeric adsorbents such as calcium alginate gel (CAG) and hard (CAH) beads were prepared to remove both the total organic acid anions (formate, acetate, propionate, etc.) and the heavy metal ions (chromium and iron) simultaneously from industrial lean methyldiethanolamine (MDEA) solvent used in the natural gas sweetening industry. These are undesirable products accumulated in the process which leads to solvent losses and contribute operational problems such as corrosion, fouling and foaming. The adsorbents were characterized using TGA, FTIR and SEM analyses. Kinetic and equilibrium studies at different temperatures including regeneration of the adsorbents were carried out. The maximum uptake capacity for the total organic acid anions using the CAG and CAH adsorbents at 23xa0°C was found to be 322.58 and 19.72xa0mg/g, respectively. Based on the high uptake, feasibility and recyclability, calcium alginate beads exhibit a great potential for MDEA solvent purification.

Removal of Oil from Water by Calcium Alginate Hydrogel Modified with Maleic Anhydride

Calcium alginate hydrogel was prepared and used as a biosorbent for the removal of oil from aqueous solutions. Calcium alginate hydrogel was further chemically modified by esterification with maleic anhydride. The changes in the physicochemical properties of maleic anhydride modified calcium alginate were investigated via multiple techniques (FTIR, SEM, BET and DSC/TGA). Adsorption batch experiments were carried out to compare the oil adsorption capacities of native and modified calcium alginates. Adsorption experiments were carried out as a function of solution pH, temperature and ionic strength to determine the optimal conditions for the adsorption of oil. Equilibrium and kinetic studies were conducted for the modified alginate. Results revealed that the maleic anhydride modification of calcium alginate improved its adsorption capacity towards oil. Higher adsorption capacities of modified alginate were attained at lower temperatures (20xa0°C), higher ionic strengths (1.0xa0M NaCl) and within the pH range of 5–9. The oil adsorption data obtained for modified alginate could be better described by the first order kinetic model (R2u2009=u20090.981) and the BET equilibrium isotherm (R2u2009=u20090.984). The maximum monolayer adsorption capacity predicted by the BET model for the modified calcium alginate was found to be 143.0xa0mg/g.

Carbon Dioxide Solubilities in Decanoic Acid-Based Hydrophobic Deep Eutectic Solvents

The solubility of CO2 in hydrophobic deep eutectic solvents (DESs) has been measured for the first time. Six different hydrophobic DESs are studied in the temperature range from 298 to 323 K and at CO2 pressures up to 2 MPa. The results are evaluated by comparing the solubility data with existing hydrophilic DESs and currently applied physical solvents and fluorinated ionic liquids. The DESs are prepared by mixing decanoic acid with a quaternary ammonium salt with different halide anions and alkyl chain lengths. The measured CO2 solubilities are similar to those found in renowned fluorinated ILs, while the heats of CO2 absorption are in the range of nonpolar solvents. The presented DESs show good potential to be used as CO2 capture agents.

Graphene as an Efficient and Reusable Adsorbent Compared to Activated Carbons for the Removal of Phenol from Aqueous Solutions

The adsorption capacity of graphene for removing phenol from aqueous solutions was evaluated and compared to those obtained for three different commercial activated carbons. In this study, graphene, W-35 activated carbon, RB2H2 activated carbon, and Nuchar granular activated carbon were investigated. Various techniques such as X-ray diffraction, BET surface analysis, and scanning electron microscopy were used to characterize the adsorbents. The adsorption of phenol onto graphene was investigated under different experimental conditions including temperature, solution pH, adsorbent dosage, and initial concentration of phenol. For comparison, adsorption experiments of phenol onto the activated carbons were also conducted. The adsorption of phenol onto graphene and activated carbons could be described by the pseudo-second-order kinetic model and the Langmuir equilibrium isotherm. The maximum adsorption capacities predicted by the Langmuir isotherm for graphene, W-35, RB2H2, and Nuchar granular activated carbons were found to be 233, 200, 91, and 167xa0mg/g, respectively. The thermodynamic study demonstrated that the adsorption of phenol onto graphene and activated carbons is a spontaneous and exothermic process. Regeneration of graphene was found to be possible using sodium hydroxide or methanol as eluents over five adsorption-desorption cycles.