N. Boujelben

Heavy metal removal from aqueous solutions by activated phosphate rock.

The use of natural adsorbent such as phosphate rock to replace expensive imported synthetic adsorbent is particularly appropriate for developing countries such as Tunisia. In this study, the removal characteristics of lead, cadmium, copper and zinc ions from aqueous solution by activated phosphate rock were investigated under various operating variables like contact time, solution pH, initial metal concentration and temperature. The kinetic and the sorption process of these metal ions were compared for phosphate rock (PR) and activated phosphate rock (APR). To accomplish this objective we have: (a) characterized both (PR) and (APR) using different techniques (XRD, IR) and analyses (EDAX, BET-N(2)); and, (b) qualified and quantified the interaction of Pb(2+), Cd(2+), Cu(2+) and Zn(2+) with these sorbents through batch experiments. Initial uptake of these metal ions increases with time up to 1h for (PR) and 2h for (APR), after then, it reaches equilibrium. The maximum sorption obtained for (PR) and (APR) is between pH 2 and 3 for Pb(2+) and 4 and 6 for Cd(2+), Cu(2+) and Zn(2+). The effect of temperature has been carried out at 10, 20 and 40 degrees C. The data obtained from sorption isotherms of metal ions at different temperatures fit to linear form of Langmuir sorption equation. The heat of sorption (DeltaH degrees), free energy (DeltaG degrees) and change in entropy (DeltaS degrees) were calculated. They show that sorption of Pb(2+), Cd(2+), Cu(2+) and Zn(2+) on (PR) and (APR) an endothermic process. These findings are significant for future using of (APR) for the removal of heavy metal ions from wastewater under realistic competitive conditions in terms of initial heavy metals, concentrations and pH.

Adsorption of nickel and copper onto natural iron oxide-coated sand from aqueous solutions: study in single and binary systems.

Natural iron oxide-coated sand (NCS), extracted from the iron ore located in North-West of Tunisia, was employed to investigate its capacity to remove copper and nickel from aqueous solutions. The aim of this work was to characterize the considered sorbent (NCS) and to assess the possibility of removing nickel and copper from aqueous solutions by this sorbent. The effects of agitation time, pH, initial metal ion concentration and temperature on the removal of these metals were studied. In order to study the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The effect of solution pH on the adsorption onto NCS was studied in the pH range from 2 to 7 and 2 to 9 for copper and nickel respectively. The adsorption was endothermic and the computation of the parameters, DeltaH degrees, DeltaS degrees and DeltaG degrees, indicated that the interactions were thermodynamically favourable. Experiments with Cu and Ni adsorption measured together showed that Cu severely interfered with Ni adsorption to the NCS and vice versa under the conditions of the two coexisted ions adsorption.

Lead removal from aqueous solutions by a Tunisian smectitic clay.

The adsorption of Pb(2+) ions onto Tunisian smectite-rich clay in aqueous solution was studied in a batch system. Four samples of clay (AYD, AYDh, AYDs, AYDc) were used. The raw AYD clay was sampled in the Coniacian-Early Campanian of Jebel Aïdoudi in El Hamma area (South of Tunisia). AYDh and AYDs corresponds to AYD activated by 2.5 mol/l hydrochloric acid and 2.5 mol/l sulphuric acid, respectively. AYDc corresponds to AYD calcined at different temperatures (100, 200, 300, 400, 500 and 600 degrees C). The raw AYD clay was characterized by X-ray diffraction, chemical analysis, infrared spectroscopy and coupled DTA-TGA. Specific surface area of all the clay samples was determined from nitrogen adsorption isotherms. Preliminary adsorption tests showed that sulphuric acid and hydrochloric acid activation of raw AYD clay enhanced its adsorption capacity for Pb(2+) ions. However, the uptake of Pb(2+) by AYDs was very high compared to that by AYDh. This fact was attributed to the greater solubility of clay minerals in sulphuric acid compared to hydrochloric acid. Thermic activation of AYD clay reduced the Pb(2+) uptake as soon as calcination temperature reaches 200 degrees C. All these preliminary results were well correlated to the variation of the specific surface area of the clay samples. The ability of AYDs sample to remove Pb(2+) from aqueous solutions has been studied at different operating conditions: contact time, adsorbent amount, metal ion concentration and pH. Kinetic experiments showed that the sorption of lead ions on AYDs was very fast and the equilibrium was practically reached after only 20 min. The results revealed also that the adsorption of lead increases with an increase in the solution pH from 1 to 4.5 and then decreases, slightly between pH 4.5 and 6, and rapidly at pH 6.5 due to the precipitation of some Pb(2+) ions. The equilibrium data were analysed using Langmuir isotherm model. The maximum adsorption capacity (Q(0)) increased from 25 to 25.44 mg/g with increasing temperature from 25 to 40 degrees C. Comparative study between sulphuric acid activated clay (AYDs) and powder activated carbon (PAC) for the adsorption of lead was also conducted. The results showed that sulphuric acid activated clay is more efficient than PAC.

Retention of nickel from aqueous solutions using iron oxide and manganese oxide coated sand: kinetic and thermodynamic studies

In this study, the removal of nickel ions from aqueous solutions using iron oxide and manganese oxide coated sand (ICS and MCS) under different experimental conditions was investigated. The effect of metal concentration, contact time, solution pH and temperature on the amount of Ni(II) sorbed was studied and discussed. Langmuir and Freundlich isotherm constants and correlation coefficients for the present systems at different temperatures were calculated and compared. The equilibrium process was well described by the Langmuir isotherm model: the maximum sorption capacities (at 29 K) were 2.73 mg Ni/g and 3.33 mg Ni/g of sorbent for ICS and MCS, respectively. Isotherms were also used to evaluate the thermodynamic parameters (ΔG°, ΔH°, ΔS°) of adsorption. The sorption kinetics were tested for the pseudo‐first‐order, pseudo‐second‐order and intra‐particle diffusion models. Good correlation coefficients were obtained for the pseudo‐second‐order kinetic model, showing that the nickel uptake process followed the pseudo‐second‐order rate expression.

Removal of nickel and cadmium from aqueous solutions by sewage sludge ash: Study in single and binary systems

Sewage sludge ash can potentially be used for the removal of metal ions from wastewater because its chemical composition is similar to that of fly ash. The aim of this work was to investigate the adsorptive characteristics of this material, including specific surface area and pH of zero point of charge (pHzpc), and to assess the possibility of removing nickel and cadmium from aqueous solutions by this sorbent. The effects of agitation time, pH, initial metal ion concentration and temperature on the removal of these metals were studied. In order to study the sorption isotherm, two equilibrium models, the Langmuir and Freundlich isotherms, were analysed. The effect of solution pH on the adsorption on to sewage sludge ash was studied in the pH range from 2 to 8. The adsorption was endothermic and the computation of the parameters, ΔH°, ΔS° and ΔG°, indicated that the interactions were thermodynamically favourable. Experiments with Ni and Cd adsorption measured together showed that Cd severely interfered with Ni adsorption to sewage sludge ash and vice versa.

Removal of Lead(II) Ions from Aqueous Solutions Using Manganese Oxide-Coated Adsorbents: Characterization and Kinetic Study:

Manganese oxide-coated sand (MOCS) and manganese oxide-coated crushed brick (MOCB) were characterized and employed for the removal of Pb(II) ions from aqueous solution. Scanning electron microscopy (SEM), FT-IR, X-ray diffraction (XRD) methods and BET analyses were used to study the surface properties of the adsorbents. Adsorption of Pb(II) ions from aqueous solutions was investigated by batch experiments. The estimated optimum pH for Pb(II) ion retention by the considered adsorbents was 5. Both the Freundlich and Langmuir isotherms provided a reasonable fit to the experimental data for the adsorption of Pb(II) ions. The adsorption capacities of the coated adsorbents at a pH value of 5 and a temperature of 20 °C were 0.029 mmol/g and 0.030 mmol/g for MOCS and MOCB, respectively. The adsorption kinetics were tested using the pseudo-first-order and pseudo-second-order equations as well as the intraparticle diffusion model, with the rate constants from the three kinetic models being calculated. The best correlation coefficients were obtained using the pseudo-second-order kinetic model. Results from this study suggest that the manganese oxide-coated sorbent is potentially suitable for the removal of Pb(II) ions from aqueous solutions.

Studies of lead retention from aqueous solutions using iron-oxide-coated sorbents.

In this research, experiments were conducted to study Pb2+ sorption onto engineered iron‐oxide‐coated sand (IOCS) and iron‐oxide‐coated crushed brick (IOCB), as well as onto naturally iron‐oxide‐coated sand (NIOCS). Optical and scanning electron microscopy (SEM) analyses were realised to investigate the surface properties and morphology of the coated sorbents. Infrared spectroscopy and X‐ray diffraction techniques were also used to characterise the sorbent structures. Adsorption of lead from synthetic aqueous solutions was investigated by batch experiments. Results show that adsorption is slightly dependent on pH. The maximum adsorption capacity obtained at pH 6 was 5, 5.5 and 2.9 mg g−1 for IOCS, IOCB and NIOCS, respectively. Both Freundlich and Langmuir isotherms can describe experimental data. The influence of temperature on the adsorption process was also evaluated. Results indicated that adsorption of Pb2+ on the three sorbents is endothermic. The thermodynamic parameters (ΔG°, ΔH° and ΔS°) for Pb2+ sorption on all considered sorbents were also determined from the temperature dependence. All considered sorbents could be an alternative emerging technology for water treatment without any side effects or treatment process alterations. However, IOCB has the best performances due to its greater capacity for the retention of lead.

Removal of phosphorus ions from aqueous solutions using manganese-oxide-coated sand and brick

AbstractManganese-oxide-coated sand (MOCS) and manganese-oxide-coated crushed brick (MOCB) were characterized and employed for the removal of phosphorus ions () from aqueous solution. Scanning electron microscope (SEM), FTIR, X-ray diffraction spectrum (XRD), and BET analyses were used to study the surface properties of the sorbents. Sorption of from aqueous solutions was investigated by batch experiments. The estimated optimum pH of phosphorus ions retention for the considered sorbents was 5. Both Freundlich and Langmuir isotherms may reasonably explain adsorption of phosphorus ions. The adsorption capacities of coated sorbents obtained at pH 5 and 20°C were 1.96 and 2.08 mg/g for MOCS and MOCB, respectively. The sorption kinetics were tested for pseudo-first order and pseudo-second order reactions as well as for intraparticle diffusion model and the rate constants of the three kinetic models were calculated. The best correlation coefficients were obtained using the pseudo-second-order kinetic model, ind...