Radiolysis performance of ibuprofen using ionizing processes: kinetics and energy consumption.

ABSTRACTIonizing technologies are used for disinfection and treatment of different industrial wastewaters. For this purpose, the radiolytic degradation of ibuprofen (IBP), selected within the main detected pharmaceuticals in different water locations with different concentrations, was investigated. Irradiation was performed with a gamma irradiator (60Co) and with electron beam accelerator. The degree of ibuprofen degradation was monitored following the evolution of its absorbance, the residual concentration by HPLC, carbon oxygen demand and total organic carbon. The degradation of IBP was higher than the removal of TOC or COD and reached 95% according to residual concentration. This pollutant (at 0.1 mM) was totally degraded when irradiated at 3 kGy and needed higher doses (7-10 kGy) for the highest concentrations (0.8-1 mM). The addition of 1 mM of persulfate ion remarkably enhanced IBP degradation by around 2 and 2.8 times for 5 and 10 kGy, respectively. Pseudo-first-order reaction kinetics could be used to depict the degradation process of IBP in all conditions. Electrical energy per order (EEO) was estimated under various conditions. The smallest EEO was obtained when gamma radiation and persulfate ion were combined. The possible degradation pathways of IBP were proposed. The results achieved in this study can be used to optimize large-scale application of nuclear techniques in water treatment in particular in treating pharmaceutical effluents.

Response Surface Methodology for Boron Removal by Donnan Dialysis: Doehlert Experimental Design.

The removal of boron by Donnan dialysis from aqueous solutions has been studied according to response surface methodology (RSM). First, a preliminary study was performed with two membranes (AFN and ACS) in order to determine the experimental field based on different parameters, such as the pH of the feed compartment, the concentration of counter-ions in the receiver compartment, and the concentration of boron in the feed compartment. The best removal rate of boron was 75% with the AFN membrane, but only 48% with the ACS membrane. Then, a full-factor design was developed to determine the influence of these parameters and their interactions on the removal of boron by Donnan dialysis. The pH of the feed compartment was found to be the most important parameter. The RSM was applied according to the Doehlert model to determine the optimum conditions ([B] = 66 mg/L, pH = 11.6 and [Cl-] = 0.5 mol/L) leading to 88.8% of boron removal with an AFN membrane. The use of the RSM can be considered a good solution to determine the optimum condition for 13.8% compared to the traditional "one-at-a-time" method.

Modelling and optimization of hexavalent chromium removal from aqueous solution by adsorption on low-cost agricultural waste biomass using response surface methodological approach.

In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.

Characterization and physicochemical aspects of novel cellulose-based layered double hydroxide nanocomposite for removal of antimony and fluoride from aqueous solution.

A series of novel adsorbents composed of cellulose (CL) with Ca/Al layered double hydroxide (CCxA; where x represent the Ca/Al molar ratio) were prepared for the adsorption of antimony (Sb(V)) and fluoride (F-) ions from aqueous solutions. The CCxA was characterized by Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), elemental analysis (CHNS/O), thermogravimetric analysis (TGA-DTA), zeta potential, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. The effects of varying parameters such as dose, pH, contact time, temperature and initial concentration on the adsorption process were investigated. According to the obtained results, the adsorption processes were described by a pseudo-second-order kinetic model. Langmuir adsorption isotherm model provided the best fit for the experimental data and was used to describe isotherm constants. The maximum adsorption capacity was found to be 77.2 and 63.1 mg/g for Sb(V) and F-, respectively by CC3A (experimental conditions: pH 5.5, time 60 min, dose 15 mg/10 mL, temperature 298 K). The CC3A nanocomposite was able to reduce the Sb(V) and F- ions concentration in synthetic solution to lower than 6 µg/L and 1.5 mg/L, respectively, which are maximum contaminant levels of these elements in drinking water according to WHO guidelines.

Optimization of boron removal from water by electrodialysis using response surface methodology.

Boron removal from water containing 5 mg L-1 of boron using electrodialysis (ED) was studied as a function of several parameters such as flow rates, initial pH, coexisting anions and ED time. An ED cell, equipped with three cation exchange membranes (fumasep FKB) and two anion exchange membranes (fumasep FAB), was applied. The central composite design, which is the standard design of response surface methodology, was used to evaluate the effects and interactions of studied factors on boron removal efficiency. The effectiveness of the considered design parameters was well examined to find the optimum condition. The experimental data obtained were analyzed by analysis of variance for the polynomial model with 95% confidence level. Boron removal by ED showed to be independent of the electrodialysis time, whereas flow rate as well as the pH of the feed solution and also the coexisting anions on the feed solution play a significant role on the deboronation efficiency. According to the desirability function, the maximum response of 43.5% was predicted for boron removal at a pH equal to 10, a flow rate of 10 L h-1, a ratio between sulfates and that of boron equal to 2 and a reaction time of 25 minutes.

Boron removal from water by adsorption onto activated carbon prepared from palm bark: kinetic, isotherms, optimisation and breakthrough curves modeling.

The occurrence of boron in water and its inefficient removal are the key issue in desalination and water treatment. Adsorption by fixed-bed column is usually used to remove mineral and organic contaminants from the aqueous phase. The adsorption of the boron onto activated carbon, prepared from palm bark, is studied. Batch adsorption experiments are developed to determine the equilibrium time and the best isotherm model. The kinetic adsorption data can be described by the second-order equation. Among the adsorption isotherm models, Langmuir and Sips models give better fit of the equilibrium data. The calculated thermodynamic parameters show that the boron adsorption is exothermic in nature. The effects of inlet boron concentration, feed flow rate and weight of activated carbon on the fixed-bed adsorption are determined by two-level factorial experimental design. Breakthrough and saturation times are higher at high adsorbent weight and low flow rates. The increase of boron initial concentration decreases breakthrough and saturation times. The volume treated per gram of activated carbon is higher at lower initial concentrations and at higher adsorbent weight. Compared to other models, the Yan model fits better the experimental data of the breakthrough curves with R2 of 0.993.

Synthesis of novel adsorbent by intercalation of biopolymer in LDH for the removal of arsenic from synthetic and natural water.

This study focuses on the synthesis of nanocomposites named CCA and CZA that were prepared by the incorporation of cellulose (CL) in the Ca/Al and Zn/Al layered double hydroxide (LDH), respectively. These materials were then used for the uptake of As(III) and As(V) from aqueous medium. Characterization of both nanocomposites (CCA and CZA) was done using FTIR and Raman analysis to identify the functional groups, N2 adsorption-desorption isotherms to determine the specific surface area and pore geometry and XPS analysis to obtain the surface atomic composition. Some other characters were investigated using simultaneous TGA and DTA and elemental chemical analysis (CHNS/O). The crystallinity of the prepared nanocomposites was displayed by XRD patterns. Furthermore, the sheet-like structure of the LDHs and the irregularity of surface morphology with porous structure were observed by TEM and SEM microphotographs. Optimization of maximum adsorption capacity was adjusted using different parameters including pH, contact time and adsorbent dosage. The pseudo-second-order model was in good fitting with kinetics results. The adsorption isotherm results showed that CZA exhibits better adsorption capacity for As(III) than CCA and the Langmuir isotherm model described the data well for both nanocomposites. Thermodynamic studies illustrated the endothermic nature of CCA and exothermic nature on CZA, as well as the fact that the adsorption process is spontaneous. A real water sample collected from well located in Gabes (Tunisia), has also been treated. The obtained experimental results were confirmed that these sorbents are efficient for the treatment of hazardous toxic species such as.

Response surface methodology for dyes removal by adsorption onto alginate calcium.

The removal of dyes from solution by adsorption onto alginate calcium beads has been studied. A methodology of surface response was used, this kind of designs estimate the coefficients of a quadratic polynomial mathematical model, whose essential interest is to be able to predict in any point of the experimental region, the values of the response. The effects of initial concentration, pH, adsorbent dose and temperature were investigated. A full factor design was performed to determine the effect of the main parameters and their mutual interaction for the adsorption process. Using the experimental results, a linear mathematical model representing the influence of the different parameters as well as their interactions was obtained; it shows that the temperature is the most significant parameter affecting the dyes' removal. The effect of various experimental parameters and optimal experimental conditions was ascertained by response surface methodology using the Doehlert model.

Removal of phosphate by Donnan dialysis coupled with adsorption onto calcium alginate beads.

In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.

Intensification of light green SF yellowish (LGSFY) photodegradion in water by iodate ions: Iodine radicals implication in the degradation process and impacts of water matrix components.

The results of this work showed that UV/IO3- oxidation process supplies good performance in the degradation of light green SF yellowish (LGSFY) dye in deionized water. This process generated reactive iodine radicals that make the degradation much faster than the sole UV irradiation. The assistance of UV-irradiation by 10 mM of iodate increased the LGSFY removal after 10 min from 36% to 90% for C0 = 10 mg/L and from 18% to 85% for C0 = 20 mg/L. In parallel, a 2.5 and 4.72-fold increase in the LGSFY initial degradation rate, as compared with UV alone, were recorded for, respectively, 10 and 20 mg/L of LGSFY. IO2 and IO played the most important role in the degradation of LGSFY by the UV/IO3- process. The degradation was not affected by the presence of chloride and nitrate ions even at high dosage levels (up to 0.1 M), whereas sulfate ions reduced the valuable effect of iodate to the half when they are present at 0.1 M. Correspondingly, humic acids, at usual concentrations as those measured in natural waters, did not affect significantly the LGSFY degradation upon photoactivated iodate process. These results revealed, in one part, that iodine radicals are selective oxidants and, in another part, that the process is likely to remove organic dyes from natural water which often contains mineral constitutes and humic substances.

Treatment of heavy metal polluted industrial wastewater by a new water treatment process: ballasted electroflocculation.

This laboratory study investigated the parameters efficiency of the new technology: ballasted electro-flocculation (BEF) using aluminum (Al) electrodes to remove cadmium and zinc from industrial mining wastewater (MWW). The principle of the BEF process is based on the use of micro-sand and polymer together to increase the weight of the flocs and the rate at which they settle is radically changing the electrocoagulation-electroflocculation settling methodology. Based on the examination of the operation parameters one by one, the best removal percentage was obtained at a current intensity of 2A, a the flow rate of 20L/h, a micro-sand dose of 6g/L, a polyéthylèneimine (PEI) polymer dose of 100mg, the contact times of 30min, a stirring speed of 50 RPM, a monopolar configuration of the electrodes, and an electrodes number of 10. The results showed that the flow rate and the current density have a preponderant effect on the variability of the quality of the settled water. In comparison, filterability was found to be more sensitive to number of electrodes, micro sand dosages and current density. It was dependent on the ratio of microsand to PEI polymer dosage, and improved when this ratio increased. Response surface methodology was applied to evaluate the main effects and interactions among stirring speed, polymer dose, current intensity, and electrodes number. The removal of Cd and Zn from industrial MWW was done for very low cost of 0.1TND/m3 equivalent to 0.04€/m3. The investigation of BEF process proposes a highly cost-effective wastewater treatment method if compared to Actiflo TM and electrocoagulation.

Hexavalent Chromium Removal from Model Water and Car Shock Absorber Factory Effluent by Nanofiltration and Reverse Osmosis Membrane.

Nanofiltration and reverse osmosis are investigated as a possible alternative to the conventional methods of Cr(VI) removal from model water and industrial effluent. The influences of feed concentration, water recovery, pH, and the coexisting anions were studied. The results have shown that retention rates of hexavalent chromium can reach 99.7% using nanofiltration membrane (NF-HL) and vary from 85 to 99.9% using reverse osmosis membrane (RO-SG) depending upon the composition of the solution and operating conditions. This work was also extended to investigate the separation of Cr(VI) from car shock absorber factory effluent. The use of these membranes is very promising for Cr(VI) water treatment and desalting industry effluent. Spiegler-Kedem model was applied to experimental results in the aim to determine phenomenological parameters, the reflection coefficient of the membrane (σ), and the solute permeability coefficient (Ps ). The convective and diffusive parts of the mass transfer were quantified with predominance of the diffusive contribution.

Application of response surface methodology and artificial neural network: modeling and optimization of Cr(VI) adsorption process using Dowex 1X8 anion exchange resin.

We report the adsorption efficiency of Cr(VI) on a strong anionic resin Dowex 1X8. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of this adsorbent were investigated. Response surface methodology was applied to evaluate the main effects and interactions among initial pH, initial Cr(VI) concentration, adsorbent dose and temperature. Analysis of variance depicted that resin dose and initial pH were the most significant factors. Desirability function (DF) showed that the maximum Cr(VI) removal of 95.96% was obtained at initial pH 5, initial Cr(VI) concentration of 100 mg/L, resin dose of 2 g and temperature of 283 K. Additionally, a simulated industrial wastewater containing 14.95 mg/L of Cr(VI) was treated successfully by Dowex 1X8 at optimum conditions. Same experimental design was employed to develop the artificial neural network. Both models gave a high correlation coefficient (RRSM(2) = 0.932, RANN(2) = 0.996).

Competitive adsorption of fluoride and natural organic matter onto activated alumina.

Natural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.

Removal of Cd(II) ions from aqueous solution and industrial effluent using reverse osmosis and nanofiltration membranes.

Industrial effluents loaded with cadmium have contributed to the pollution of the environment and health troubles for humans. Therefore, these effluents need treatment to reduce cadmium concentration before releasing them to public sewage. The purpose of the research is to study the major role of reverse osmosis (RO) and nanofiltration (NF) processes, which can contribute to the removal of cadmium ions from model water and wastewater from the battery industry. For this reason, two RO and two nanofiltration membranes have been used. The effects of feed pressure, concentration, ionic strength, nature of anion associated with cadmium and pH on the retention of Cd(II) were studied with model solutions. Thereafter, NF and RO membranes were used to reduce cadmium ions and total salinity of battery industry effluent. Among these membranes, there are only three which eliminate more than 95% of cadmium. This was found to depend on operating conditions. It is worth noting that the Spiegler-Kedem model was applied to fit the experimental results.

Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

Iron removal from brackish water by electrodialysis.

The aim of this work is to study the removal of iron from brackish water using electrodialysis (ED). Experiments were carried out on synthetic brackish water solutions using a laboratory-scale ED cell. The influence of several parameters on process efficiency was studied. This efficiency is expressed by the removal rate, transport flux, current efficiency and power consumption. The applied voltage, the feed flow rate, the pH and iron initial concentration ofthe feed solution have a significant effect on the process efficiency and mainly on the iron transfer from dilute to concentrate compartment. Nevertheless, feed ionic strength does not have an effect on the iron removal. However, the effect is only noted on the specific power consumption.