In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X‐ray diffraction, elemental analysis X‐ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo‐second‐order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.
A multiscale investigation including computational chemistry calculations and experimental studies was performed to elucidate and understand the methylene blue (MB) adsorption on polyaniline (PANI) from an aqueous solution. Static DFT and DFT-based ab initio molecular dynamics were used to characterize the intermolecular interactions of this dye molecule with nondoped and doped PANI. Experimental adsorption studies at different operating conditions were performed to complement the mechanism analysis of this adsorption system. Infrared spectroscopy studies and ab initio calculations showed the important role of π-π stacking and van der Waals interactions for the dye adsorption on PANI. Experimental results of MB adsorption on the PANI surface indicated that alkaline conditions were more favorable than acidic conditions where the MB adsorption capacity ranged from 9.91 mg/g at pH 1.8 to 23.16 mg/g at pH 10.9. Equilibrium adsorption studies with nondoped PANI revealed a fast removal of the dye molecules where the equilibrium adsorption was reached after 45 minutes. The kinetic parameters were calculated with the pseudo-second and pseudo-first order models, while the adsorption mechanism was analyzed using the intraparticle diffusion, Boyd, and Elovich models. Dye adsorption equilibrium was studied at pH 8 and 30 °C where Temkin, Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) isotherm models as well as a statistical physics monolayer model were employed in data analysis. The saturation dye adsorption capacity was 40.2 mg/g where an inclined adsorption orientation of dye molecules on the PANI surface could be expected with an adsorption energy of 14.0 kJ/mol. This interaction energy clearly indicated that only physical interactions were involved in the MB dye adsorption mechanism, which was also confirmed by the calculations with the D-R isotherm model. These theoretical and experimental results are important to understand the dye adsorption properties of conductive polymers and to consolidate their application in the synthesis of new adsorbents and composites for water treatment.
The objective of this study is to present numerical aspects related to the implementation of the interaction integral method for the purpose of determining the stress intensity factors in mode I and mixed-mode crack problems of functionally graded materials (FGM) and homogenous materials for a different form of cracking. This numerical development is based on the use of the finite element method (FEM), by the coupling of the Ansys-Matlab calculation codes. To validate the accuracy and reliability of the approach, the results obtained will be compared with other numerical results in the literature. The interaction integral method is one of the methods most compatible with the formulation of the finite element method. Therefore, we are interested in this study, in terms of the presentation of necessary steps which allow the resolution of a problem by finite elements for the mechanical problems. It is very important to note that the principle of the implementation of the “Integral M†technique is using scripts based on the coupling of two commercial software.
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