The use of encapsulation as a proposed solution to avoid problems encountered with conventional materials in powder form Application in methylene blue removal from aqueous solutions

International audienceThe Ziziphus jujuba stones chemically modified with orthophosphoric acid (PZJS), then encapsulated with sodium alginate (BZJS1 and BZJS2) were used for organic dye adsorption. In this context, the basic dye methylene blue (MB) was chosen as a test molecule. The characteristics of the prepared beads were examined by different characterization techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray diffraction (EDX), X-ray fluorescence (XRF), Thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller method (BET) with nitrogen adsorption-desorption isotherm at 77 °K. In a batch system, initial pH (2−12), temperature (10, 25, 30 and 40 °C), initial concentration (50–200 mg/L), contact time, salt and organic compound effects were studied. The obtained results showed that the maximum MB adsorption amounts were 737.13 mg/g and 660.12 mg/g onto BZJS1 and BZJS2 at ambient temperature respectively, showing that the prepared materials are more efficient than most of the other adsorbents. Moreover, experimental data modeling showed that the adsorption process followed the Redlich-Peterson model. Regarding kinetics modeling, pseudo-first-order (PFO), pseudo-second-order and Pseudo-nth order models were used to correlate experimental data, demonstrating that a mass transfer equation (PFO) could describe MB adsorption. Thermodynamic parameters were also evaluated, demonstrating that the MB adsorption process was achievable, spontaneous and exothermic. The regeneration study showed that both of the beads had excellent adsorption efficiency even at the sixth cycle for the two beads, 92.01 and 82.88 for BZJS1 and BZJS2, respectively. From this and in view of a future implementation at industrial scale, encapsulation by sodium alginate polymer can be therefore promisingly proposed as a solution to avoid the problems of conventional materials in powder form, such as the difficulty of regeneration, performances and mass loss during the recovery step of the powder from the medium. © 202

Molecular dynamic simulation and DFT computational studies on the adsorption performances of methylene blue in aqueous solutions by orange peel-modified phosphoric acid

International audienceAdsorptive removal of methylene blue dye (MB) from aqueous medium using orange peels treated with phosphoric acid (OP-H3PO4) was examined. The OP-H3PO4 was characterized using Fourier transform Infra-red spectroscopy, X-ray diffraction, scanning electron microscopy, Energy Dispersive X-ray Spectroscopy, and thermogravimetric analysis. The effect of different process parameters, namely contact time, initial dye concentration, initial solutions pH, and temperature effect were examined. Equilibrium experimental data were fitted by Langmuir, Freundlich, Redlich-Peterson (R-P) and Sips isotherm models. For the two-parameter models, the data fitted well with the Langmuir isotherm model suggesting a monolayer adsorption of the dye onto the homogeneous adsorbent surface. However, regarding the three-parameter models, for the whole temperature range, both the sips and the Redlich-Peterson models showed high correlation factors, indicating that calculated data were close to those found experimentally and suggesting that MB adsorption occurs on both homogeneous and heterogeneous surfaces of OP-H3PO4 The present study revealed that OP-H3PO4 is an effective and efficient adsorbent for the removal of basic dyes from aqueous solution. In addition, quantum chemical calculations realized with density functional theory (DFT) method were successfully considered to correlate the experimental results. Moreover, the molecular dynamics simulations (MDS) were used to simulate the interactions between the MB molecule and the OP-H3PO4 (110) surface, indicating that the MB molecule adsorbs onto the OP-H3PO4 (110) surface in a nearby horizontal position. (C) 2019 Elsevier B.V. All rights reserved

Thermodynamic study and the development of a support vector machine model for predicting adsorption behavior of orange peel-derived beads in wastewater treatment

International audienceThis study investigates the use of orange peels as a precursor for synthesizing sodium alginate -encapsulated beads for methylene blue (MB) removal. The prepared beads (BOP1 and BOP2) underwent characterization through FTIR, XRF, SEM and TGA. Subsequently, the impacts of various factors, including temperature, the initial pH, initial concentration, salt and humic acid, are studied. The adsorption isotherms show high adsorbed quantities of 764.92 and 659.78 mg/g for BOP1 and BOP2 respectively, while the obtained data are best described by the monolayer with two energies (MMTE) model, which is then used to perform a thermodynamic study of the MB adsorption mechanism. Additionally, the adsorption kinetics data are modeled using three models, with the PFO model identified as the most appropriate. The regenerated beads demonstrate the ability to be reused up to 7 cycles, The effects of NaCl and humic acid on MB adsorption reveal that NaCl inhibits adsorption due to competition with Na +, while humic acid has no effect. Finally, a support vector machine (SVM) model optimized by the Levy Flight Distribution Optimization (LFD) algorithm is developed and found to be capable of accurately predicting the adsorption behavior of the prepared beads. This model is then used in optimizing the process conditions for maximal MB removal. Overall, this study demonstrates that the prepared beads could be potential low-cost and environmentally friendly adsorbents for wastewater treatment applications

The Enhanced Adsorption Capacity of Ziziphus jujuba Stones Modified with Ortho-Phosphoric Acid for Organic Dye Removal: A Gaussian Process Regression Approach

International audienceHere, the chemical modification of Ziziphus jujuba stones (ZJS) treated with ortho-phosphoric acid (ZJS-H3PO4) is investigated to enhance its adsorption properties for organic dyes. The physicochemical properties of ZJS-H3PO4 reveal increased porosity (87.29%), slightly higher bulk density (0.034 g mL−1), and enhanced acidity (31.42 m eq g g−1) compared to untreated ZJS. XRF analysis confirms the successful incorporation of orthophosphoric acid during treatment due to a significant increase in phosphorus content. The maximum adsorption capacity of methylene blue on ZJS-H3PO4 is found to be 179.83 mg g−1, demonstrating its efficacy as a potential adsorbent for organic dyes. These findings suggest that modifying ZJS with orthophosphoric acid could be a promising strategy to enhance its adsorption performance in various environmental applications. Furthermore, Gaussian process regression (GPR) is employed to model MB adsorption by ZJS-H3PO4. Optimization of the GPR model involves evaluating different kernel functions and meticulously adjusting parameters to maximize its ability to capture complex relationships in the data. The obtained GPR model demonstrates remarkable performance with high correlation coefficients (R) and low root mean square errors (RMSEs) across all study phases. Model validation is performed through residual analysis, confirming its effectiveness and accuracy in predicting MB adsorption. Finally, a user-friendly interface is developed to facilitate the usage of the GPR model in future applications, representing a significant advancement in environmental process modeling and ecosystem management