Reducing the environmental impacts of desalination reject brine using modified Solvay process based on calcium oxide

This is the final version. Available from MDPI via the DOI in this record. : In this research, the influence of a variety of operational factors such as the temperature of the reaction, gas flow rate, concentration of NaCl, and the amount of Ca(OH)₂ for reducing the environmental impacts of desalination reject brine using the calcium oxide‐based modified Solvay process were investigated. For this purpose, response surface modeling (RSM) and central compo‐ site design (CCD) were applied. The significance of these factors and their interactions was assessed using an analysis of variance (ANOVA) technique with a 95% degree of certainty (p < 0.05). Optimal conditions for this process included: a temperature of 10 °C, a Ca(OH)₂/NaCl concentration ratio of 0.36, and a gas flow rate of 800 mL/min. Under these conditions, the maximum sodium removal efficiency from the synthetic sodium chloride solution was 53.51%. Subsequently, by employing the real brine rejected from the desalination unit with a 63 g/L salinity level under optimal conditions, the removal rate of sodium up to 43% was achieved. To investigate the process’s kinetics of Na elimination, three different kinds of kinetics models were applied from zero to second order. R squared values of 0.9101, 0.915, and 0.9141 were obtained in this investigation for zero‐, first‐, and second‐degree kinetic models, respectively, when synthetic reject saline reacted. In contrast, accord‐ ing to R squared’s results with utilizing real rejected brine, the results for the model of kinetics were: R squared = 0.9115, 0.9324, and 0.9532, correspondingly. As a result, the elimination of sodium from real reject brine is consistent with the second‐order kinetic model. According to the findings, the calcium oxide‐based modified Solvay method offers a great deal of promise for desalination of brine rejected from desalination units and reducing their environmental impacts. The primary benefit of this technology is producing a usable solid product (sodium bicarbonate) from sodium chloride in the brine solution

Performance enhancement of specific adsorbents for hardness reduction of drinking water and groundwater

This is the final version. Available from MDPI via the DOI in this record. One of the most advantageous methods for lowering water hardness is the use of low-cost adsorbents. In this research, the effectiveness of natural zeolite (clinoptilolite type), activated carbon, and activated alumina was evaluated. These adsorbents were sequentially modified by NaCl, HCl, and NaCl-HCL to improve their ability to adsorb. The contact time and the amount of adsorbent used in the adsorption process were investigated experimentally to determine their effects. The results indicated that the best contact time for hardness reduction was 90 min, and the best concentrations of adsorbents in drinking water for zeolite, activated carbon, and activated alumina were 40, 60, and 60 g/L, respectively. In addition, for groundwater, these figures were 60, 40, and 40 g/L, respectively. The greatest possible decreases in total hardness under the best conditions by natural zeolite, activated carbon, and activated alumina adsorbents were 93.07%, 30.76%, and 56.92%, respectively, for drinking water and 59.23%, 15.67 %, and 39.72% for groundwater. According to the results obtained from experiments, NaCl-modified zeolite, natural zeolite, and NaCl-HCl-modified activated carbon performed better in terms of parameter reduction. The equilibrium data were well fitted by the Langmuir isotherm model, whereas the kinetic data for the adsorption process were consistent with the pseudo-second-order model. The equilibrium study of the adsorption process by the Morris–Weber model revealed that both chemical and physical adsorption are involved.Bushehr Water & WasteWater Company (Iran

Application of Photo-Fenton, Electro-Fenton, and Photo-Electro-Fenton processes for the treatment of DMSO and DMAC wastewaters

This is the final version. Available from Elsevier via the DOI in this record. Biological treatment, due to the formation of hazardous chemicals to remove organic compounds such as dimethyl sulfoxide (DMSO) and N, N-dimethylacetamide (DMAC), has limited potential. Advanced oxidation processes (AOPs) are regarded as a viable alternative for treating molecules containing carbon-hydrogen bonds that cannot be broken down by traditional physico-chemical methods. In this investigation, various AOPs such as Photo-Fenton, Electro-Fenton, and Photo-Electro-Fenton processes were studied to treat wastewaters containing DMSO and DMAC. The effects of the operating parameters, including various initial concentrations of DMSO and DMAC, initial pH, reaction time, different concentrations of Fenton's reagent, power of UV lamp, different concentrations of electrolytes, the distance between electrodes and current intensity, were investigated. The findings of the experiments revealed that a pH of 3 and a reaction time of 120 min were optimal. At 2000 mg L−1 of DMSO, maximum degradation and the final concentration of TOC were 98.64 % and 256.8 mg L−1, respectively, by the Electro-Fenton process under the optimal conditions. The Electro-Fenton process was successful in determining the maximum degradation of DMAC (96.31 %) and the final TOC concentration (10.03 mg L−1) at 250 mg L−1 of DMAC under optimal conditions. Finally, it can be concluded that the Electro-Fenton process was the best process for the efficient removal of DMSO and DMAC. The second step of the kinetic model follows a pseudo-first-order reaction for 250 and 500 mg L−1 of pollutants and obeyed a pseudo-second-order kinetic model for concentrations of 1000, 2000 mg L−1.Bushehr province water company, Ira

Alginate-based electrospun core/shell nanofibers containing dexpanthenol: A good candidate for wound dressing

The skin prevents infection and contamination entering the body, and wound dressings are one of the most serious tools in wound healing. In the present work, the biocompatibility and swelling tendency of nanofibers increased by adding alginates to a polymer solution is investigated. Glutaraldehyde was used in different methods to strengthen nanofibers, and it was found that a better cross-link was made from the combination of glutaraldehyde with the polymer solution before electrospinning. As the use of drug accelerates the healing process, dexpanthenol was added to the polymeric composition of polyvinyl alcohol (PVA) and sodium alginate (SA) using a blending method. The resulting composition was then used as the core of the nanofibers, and drug release was controlled by different shells. The results showed that the presence of chitosan 1% (w/v) in the shell side of nanofibers helped better control the drug release. Also, the drug release from dexpanthenol-loaded wound dressing followed the Fickian diffusion mechanism with the Korsmeyer-Peppas model. MTT analysis and cell culture indicated that dexpanthenol-loaded PVA/SA/Triton-Chitosan nanofibers not only were nontoxic to the fibroblast cells but also appropriately affected the cellular attachment and morphology. It was revealed that PVA/SA/Triton-Chitosan nanofibers could be used for tissue engineering applications

Fabrication, characterization and in vivo evaluation of dexpanthenol sustained-release nanofibers for wound healing

In this study, wound dressings consisting of dexpanthenol (Dex)-loaded electrospun nanofibers were fabricated using polyvinyl alcohol (PVA)/sodium alginate (SA), and chitosan as the core and the shell, respectively. Considering the remarkable properties of chitosan, it was used as a shell against drug release and to improve the thermal stability, and tensile strength of the scaffold. By comparing the thermogravimetric, and tensile strength results of nanofibers with and without shell, it was revealed that the presence of chitosan in the shell side could improve the thermal stability and increased the tensile strength by about three times. The isotherm models of dexpanthenol release from the PVA/SA/Dex-CS scaffold was best described by the Langmuir model. Besides, Fourier transform infrared, scanning electron microscopy, and X-ray diffraction techniques were performed to characterize nanofibers. Furthermore, an in vivo investigation of a wound dressing with dexpanthenol showed better healing compared to the wound dressings without dexpanthenol

Co-sensitization of natural and low-cost dyes for efficient panchromatic light-harvesting using dye-sensitized solar cells

Co-sensitization is an effective strategy to achieve panchromatic light-harvesting and to enhance dye-sensitized solar cell performance. In this work, the potential of the extracted natural dyes from Malva verticillata and Syzygium cumini was evaluated as mono and co-sensitizers in DSSCs. The UV–vis absorption spectra revealed that the combination of studied dyes had a high molar extinction coefficient and cumulative absorption properties in a way that its absorption spectra overlapped the spectral domain where the original sensitizers lacked light-harvesting. Moreover, all investigated dyes were characterized using circular dichroism, dynamic light scattering, zeta potential, cyclic voltammetry, and Fourier-transform infrared spectroscopy. The results of zeta potential analysis showed that the pigment aggregation and their colloidal stability, which has implications for the pigment adsorption process on TiO2 nanoparticles, were effectively controlled by varying the pH of the dye extract. Based on the CV results, the studied dyes indicated excellent redox stability and sufficient thermodynamic driving force for efficient electron injection. Based on the photovoltaic results, the acidified cocktail-DSSC had the highest and of 3.15 mA and 1.84 %, respectively. This superiority could be ascribed to the panchromatic light-harvesting, the excellent optical activity, and the appropriate energy levels of the acidified cocktail. Moreover, the loading of acidified cocktail dyes on the TiO2 surface was enhanced due to their homogeneous dispersion, less steric hindrances, and multi-anchor groups attached to the semiconductor surface. Based on the stability results, the treated cocktail-DSSC retained about 52.51 % of its as-fabricated efficiency after seven days while NDSSCs sensitized with acidified Syzygium cumini, Malva verticillata, Syzygium cumini, and cocktail retained about 26.24 %, 14.80 %, 16.35 %, and 15.25 %, respectively

Efficiency and stability improvement of natural dye‐sensitized solar cells using the electrospun composite of TiO 2 nanofibres doped by the bio‐Ca nanoparticles

The dye-sensitized solar cells (DSSCs) can be effectively improved and stabilized by outstanding electrical and morphological characteristics of TiO2 nanofibres combined with bio-calcium doping. The pristine and bio-Ca-doped TiO2 nanofibres were fabricated using a cost-effective electrospinning technique. Biocompatible calcium carbonate nanoparticles (bio-Ca) were synthesized from the cuttlebone of Sepia Pharaonis. Moreover, a facile one-step procedure was employed to fabricate efficient TiO2 nanofibres-based DSSCs using a Pechini-type sol. This approach produced a highly porous dense film of TiO2 upon sintering without the need for the hot-pressing or adhesion layer steps. Based on the results, the DSSCs fabricated by the bio-Ca-doped TiO2 nanofibres showed the highest Isc, Voc, and η of 2.19 mA, 0.41 V, and 1.48% respectively. This superiority could be due to the higher specific surface area and the relatively smaller average diameter observed for bio-Ca-doped TiO2 nanofibres, which improved dye-loading and guided electron transport respectively. In addition, Ca2+ doping significantly suppressed the photocatalytic activity in the bio-Ca-doped TiO2 nanofibres owing to the formation of the TiO2 rutile-anatase combined phase. Besides, the substitution of Ti4+ with Ca2+ positively affects the conduction band of TiO2 and causes trap sites that retard the charge recombination. Our results also demonstrated that the bio-Ca-doped TiO2 nanofibres-based DSSC maintained about 78.38% of its initial efficiency after two weeks, while DSSCs fabricated by the TiO2 nanofibres and TiO2 nanoparticles retained 63.71% and 27.38% respectively. The superior stability could be due to the combined effect of nanoparticles into nanofibres transformation and bio-Ca doping