Advances and future perspectives of water defluoridation by adsorption technology: A review.

Fluoride contamination in water sources poses a significant challenge to human health and the environment. In recent years, adsorption technology has emerged as a promising approach for water defluoridation due to its efficiency and cost-effectiveness. This review article comprehensively explores the advances in water defluoridation through adsorption processes. Various adsorbents, including natural and synthetic materials, have been investigated for their efficacy in removing fluoride ions from water. The mechanisms underlying adsorption interactions are elucidated, shedding light on the factors influencing defluoridation efficiency. Moreover, the review outlines the current state of technology, highlighting successful case studies and field applications. Future perspectives in the field of water defluoridation by adsorption are discussed, emphasizing the need for sustainable and scalable solutions. The integration of novel materials, process optimization, and the development of hybrid technologies are proposed as pathways to address existing challenges and enhance the overall efficacy of water defluoridation. This comprehensive assessment of the advances and future directions in adsorption-based water defluoridation provides valuable insights for researchers, policymakers, and practitioners working towards ensuring safe and accessible drinking water for all.

Green synthesis of Ag2O nanoparticles using Punica granatum leaf extract for sulfamethoxazole antibiotic adsorption: characterization, experimental study, modeling, and DFT calculation.

Silver oxide (Ag2O) nanoparticles (NPs) were generated by synthesizing green leaf extract of Punica granatum, and afterwards they were used as adsorbent to remove the antibiotic additive sulfamethoxazole (SMX) from aqueous solutions. Prior of their use as adsorbent, the Ag2O NPs were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX), and transmission electron microscopy (TEM). The Ag2O NPs were found to be spherically shaped and stabilized by the constituents of the extract. Further, at SMX antibiotic concentration of 100 mg L-1, the Ag2O NPs achieved almost complete removal of 98.93% within 90 min, and by using 0.8 g L-1 of adsorbent dose at pH=4 and temperature T=308 K. In addition, the experimental data were well fitted with the theoretical Langmuir model indicating homogeneous adsorbed layer of the SMX antibiotic on the Ag2O NPs surface. The maximum uptake capacity was 277.85 mg g-1. A good agreement was also found between the kinetic adsorption data and the theoretical pseudo-second-order model. Regarding the thermodynamic adsorption aspects, the data revealed an endothermic nature and confirmed the feasibility and the spontaneity of the adsorption reaction. Furthermore, the regeneration study has shown that the Ag2O NPs could be efficiently reused for up to five cycles. The geometric structures have been optimized and quantum chemical parameters were calculated for the SMX unprotonated (SMX+/-) and protonated (SMX+) using density functional theory (DFT) calculation. The DFT results indicated that the unprotonated SMX+/- reacts more favorably on the Ag2O surface, as compared to the protonated SMX+. The SMX binding mechanism was predominantly controlled by the electrostatic attraction, hydrogen bond, hydrophobic, and π-π interactions. The overall data suggest that the Ag2O NPs have promising potential for antibiotic removal from wastewater.

Photocatalytic degradation of cefixime in aqueous solutions using functionalized SWCNT/ZnO/Fe3O4 under UV-A irradiation.

In this study, SWCNT/ZnO/Fe3O4 heterojunction composite was prepared for enhancing the degradation of ß-lactam drugs such as cefixime (CFX) from an aqueous solution. The effects of several factors such as pH, initial concentration of CFX, and photocatalyst dose were investigated. Among them, pH was the most effective parameter for the degradation of CFX. Pareto graph revealed that the degradation process was accelerated at acidic conditions. The surface morphology test such as scanning electron microscopy (SEM) was applied to enlighten the surface of the functionalized SWCNT/ZnO/Fe3O4 photocatalyst. Highly advanced analyzes such as X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive Spectrometry (EDX), Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and point of zero charge were included to explain the structure of the photocatalyst. The response surface methodology's results show that the optimum CFX efficiency was fully achieved at 94.19%. The optimal conditions with lower standard error (2.08) were given as pH of 5.93, 22.76 ppm of CFX, and 0.46 g L-1 of the amount of photocatalyst. Besides, the obtained photocatalyst can be easily used many times owing to its high reusability. SWCNT/ZnO/Fe3O4 photocatalyst might be recommended to be used for the mineralizing of drug compounds such as antibiotics in water. Moreover, thiazol-2-ol, N-(dihydroxymethyl)-2-(2-hydroxythiazol-4-yl)acetamide,(S)-N-(2-amino-1-hydroxy-2-oxoethyl)-2-(2 hydroxythiazol-4-yl), and 2-(2-hydroxythiazol-4-yl)-N-((2R,3R)-2-mercapto-4-oxoazetidin-3-yl)acetamide were among the detected intermediates products from the cefixime degradation in the process.

Boron removal from aqueous solutions by chitosan/functionalized-SWCNT-COOH: Development of optimization study using response surface methodology and simulated annealing.

Boron contamination in water resources (especially drinking waters and agricultural land) is a major problem for the ecosystem. In this study, a novel synthesized chitosan/functionalized-SWCNT-COOH was prepared to separate boron (as boric acid) from aqueous solutions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that SWCNT was dispersed in chitosan homogenously. Moreover, this study has related to the constrained optimization problem with an engineering approach. Response surface method (RSM) with face-centered central composite design (FCCCD) was chosen for maximizing the adsorption capacity as well as determining optimal independent factors such as pH, adsorbent dose, and concentration of boric acid. The optimized response (adsorption capacity) was reached 62.16 mg g-1 under the optimal conditions (98.77 mg L-1 of boric acid concentration, pH of 5.46 and 76 min). The present study has indicated that the synthesized material can be used as an adsorbent for eliminating boric acid from aqueous solutions depending on its high adsorbent capacity to remove boron and has better performance than existing adsorbents. Furthermore, simulated annealing (SA) optimization technique was used to compare the findings of RSM. Moreover, the selected optimization techniques were compared with error functions. The optimal conditions derived from SA were 91.17 mg L-1 of boric acid concentration, pH of 5.86, and 76.17 min. The optimal adsorption capacity of SA was found to be 62.06 mg g-1. These results revealed that the predictions of the two models are very close to each other.

Structural and adsorption behaviour of ZnO/aminated SWCNT-COOH for malachite green removal: face-centred central composite design.

In this study, an effective adsorbent was synthesized to remove malachite green (MG), which is one of the toxic dyes. Firstly, single walled carbon nanotube with carboxylated acid (SWCNT-COOH) was functionalized with diethylenetriamine and a new nanocomposite was obtained using nano zinc oxide (ZnO) powder. The effects of pH (3-7), the amount of adsorbent (5-15 mg) and the initial concentration (10-50 mg L-1) of the solution on the adsorption uptake were investigated. The optimal parameters that maximize the adsorption uptake according to the specified working range are found to be 4.63 for pH, 49.94 mg L-1 for initial concentration, 5.25 mg for the adsorbent dose, and the maximum adsorption capacity has been found as 52.26 mg g-1. The excellent fitting of the pseudo-second kinetic model with (R2 = 0.9912) was fitted the experimental data. The Freundlich isotherm model gave a clue about the type of adsorption. Furthermore, thermodynamic results showed that adsorption process was endothermic.

Preparation of ZnO/BaTiO3 adsorbent using Elaeagnus Angustifolia L. leaf extract and its evaluation for ciprofloxacin removal from aqueous solutions: an optimization study.

Especially, most papers have reported an increase in antibiotic resistance (AR) bacterial infections during the COVID-19 pandemic. Because of the outbreak of the SARS-CoV-2, antimicrobial resistance (AMR) should be controlled and reduced. Researchers have reported that the adsorption technique is an sufficient procedure for separating drugs such as antibiotics from aqueous solutions. The prepared of ZnO/BaTiO3 nanocomposite using Elaeagnus Angustifolia L. leaf extract was successfully obtained using green route. The synthesized nanocomposite was interacted with ciprofloxacin hydrochloride (CPF) to aim at eliminating the antibiotic from aqueous solutions. The incorporation of Elaeagnus Angustifolia leaf extract onto ZnO/BaTiO3 proved a sustainable chemistry study. Hence, this study indicated that green nanoparticles include neither the use of hazardous chemicals nor toxic chemicals. FTIR, XRD, and SEM-EDX analyses were applied to give information about the structural properties of the green nanocomposite. Box-Behnken design (BBD) was executed by response surface methodology (RSM) to gain optimal conditions. The effect of pH, initial concentration of CPF, and nanocomposite dose on CPF-nanocomposite interaction was examined. The experimental findings of adsorption study revealed that the optimal adsorption capacity of CPF onto ZnO/BaTiO3 was found as 125.29 mgg-1 under optimal conditions (adsorbent dose: 3.00 mg, pH value of solution: 9.88, initial concentration CPF: 49.63 mgL-1).

Comparison of microwave-assisted techniques for the extraction of antioxidants from Citrus paradisi Macf. biowastes.

Microwave-assisted extraction (MAE) and solvent-free microwave extraction and Soxhlet extraction were applied to Ray Ruby grapefruit leaves (Citrus paradisi Macf.) to compare extract efficiency. Face centered composite designs were constructed via response surface methodology. Effects of factors of MAE were investigated on total phenolic content (TPC) and naringin content (NC). The optimized conditions were established as 1.4 kWL-1 for microwave power density, 20.00 gL-1 for solid/solvent ratio, 218.180 s for extraction time, while responses were calculated as 14.210 mg of gallic acid equivalent per g of the dried leaf (mg GAE g-1DL) and 13.198 mg of naringin per g of dried leaf (mg Ng-1DL) for TPC and NC, respectively. SFME and classical Soxhlet methods were also conducted for comparison reasons.

Kinetics and thermodynamics evaluation of oxidative stability in Oleum hyperici: A comparative study.

In this study, Oleum hyperici (St. John's Wort oil) was investigated according to its oxidative stability and antioxidant activity parameters. A homemade and two different brands of oils were used for comparative reasons. Oxidation process regarding kinetics and thermodynamics studies achieved by accelerated Rancimat conditions (100-140 °C). The quality parameters of the oil samples were compared depending on phenolic and flavonoid contents, antioxidant activity, free fatty acid quantity and shelf-life. Principal component analysis (PCA) has been also applied to comprehend the relationship between these three groups and their quality parameters. The homemade oil has been predicted to have almost twice longer shelf-life than that of the commercial ones (119 days versus 66/69 days). Additionally, lipid oxidation in the St. John's Wort oils has been found to be endothermic and non-spontaneous depending on the thermodynamic indexes.

Optimization of ultrasound-assisted extraction of phenolic compounds from grapefruit (Citrus paradisi Macf.) leaves via D-optimal design and artificial neural network design with categorical and quantitative variables.

BACKGROUND: The extraction of phenolic compounds from grapefruit leaves assisted by ultrasound-assisted extraction (UAE) was optimized using response surface methodology (RSM) by means of D-optimal experimental design and artificial neural network (ANN). For this purpose, five numerical factors were selected: ethanol concentration (0-50%), extraction time (15-60 min), extraction temperature (25-50 °C), solid:liquid ratio (50-100 g L-1 ) and calorimetric energy density of ultrasound (0.25-0.50 kW L-1 ), whereas ultrasound probe horn diameter (13 or 19 mm) was chosen as categorical factor. RESULTS: The optimized experimental conditions yielded by RSM were: 10.80% for ethanol concentration; 58.52 min for extraction time; 30.37 °C for extraction temperature; 52.33 g L-1 for solid:liquid ratio; 0.457 kW L-1 for ultrasonic power density, with thick probe type. Under these conditions total phenolics content was found to be 19.04 mg gallic acid equivalents g-1 dried leaf. CONCLUSION: The same dataset was used to train multilayer feed-forward networks using different approaches via MATLAB, with ANN exhibiting superior performance to RSM (differences included categorical factor in one model and higher regression coefficients), while close values were obtained for the extraction variables under study, except for ethanol concentration and extraction time. © 2018 Society of Chemical Industry.