Interaction of some essential amino acids with synthesized poorly crystalline hydroxyapatite

This study focused on the release of two essential amino acids, l-lysine and dl-leucine, previously adsorbed onto poorly crystalline hydroxyapatite of Ca/P = 1.59, synthesis by precipitation methods. The composition of the calcium-deficient hydroxyapatite (CDHA) is chemically and structurally similar to the bone mineral. Their surface reactivity is indeed linked to the existence of hydrated surface particles (HPO42- and Ca2+). The adsorption kinetics is very fast while the release kinetics is relatively slow. The adsorption rate reached approximately 70%, but the release rate did not exceed 12%. The chemical composition of solution has an influence on the release processes. The presence of phosphate ions favored the release of amino acids, while the calcium ions inhibited it. Also, the release process is slightly influenced by Ra (ml/mg) ratio and incubation temperature of the medium. The charged –COO− and NH3+ of amino acids are the strongest groups that interact with the surface of hydroxyapatite, the adsorption is mainly due to the electrostatic interaction between the groups –COO− of amino acids and calcium Ca2+ ions of the hydroxyapatite. dl-Leucine (non-polar) and l-Lysine (polar–basic) interact with the hydroxyapatite surface in the zwitterionic and cationic forms, respectively. The study of interactions between amino acids and hydroxyapatite is carried out in vitro by using UV–vis and infrared spectroscopy IR techniques

Adsorption/desorption of Direct Yellow 28 on apatitic phosphate: Mechanism, kinetic and thermodynamic studies

In this study, the adsorption potential of apatitic tricalcium phosphate for the removal of Direct Yellow 28 (DY28) from aqueous solution has been investigated by using batch mode experiments. The effects of different parameters such as pH, adsorbent dosage, initial dye concentration, contact time, addition of ions and temperature have been studied to understand the adsorption behavior of the adsorbent under various conditions. The adsorbent has been characterized by pHzpc measurement, chemical analyses, FTIR, XRD and TEM. The Langmuir and Freundlich models are found to be the best to describe the equilibrium isotherm data, with a maximum monolayer adsorption capacity of 67.02 mg g−1. Thermodynamic parameters including the Gibbs free energy ΔG, enthalpy ΔH, and entropy ΔS have revealed that the adsorption of DY28 on the apatitic tricalcium phosphate is feasible, spontaneous and endothermic. Among the kinetic models tested for apatitic tricalcium phosphate, the pseudo-second-order model fits the kinetic data well. The introduction of orthophosphate ions in the medium causes a decrease of adsorption. The addition of Ca2+ ions favors the adsorption. The results of this study have demonstrated the effectiveness and feasibility of the apatitic tricalcium phosphate for the removal of DY28 from aqueous solution

Removal of fluoride from aqueous solution by adsorption on hydroxyapatite (HAp) using response surface methodology

A study on the adsorption of fluoride onto hydroxyapatite was conducted and the process parameters were optimized using Response Surface Methodology (RSM). Hydroxyapatite has been characterized by using different physicochemical methods. In order to determine the effects of process parameters namely temperature (20–40 °C), initial solution pH (4–11), adsorbent dose (0.1–0.3 g) and initial fluoride concentration (10–20 mg L−1) on fluoride uptake from aqueous solution, a three-level, four-factor, Box–Behnken design has been employed. The second order mathematical model was developed by regression analysis of the experimental data obtained from 29 batch runs. The optimum pH, temperature, adsorbent dose and initial concentration were found by desirability function to be 4.16, 39.02 °C, 0.28 g and 20 mg L−1, respectively. Fluoride removal was 86.34% at the optimum combination of process parameters. Dynamic adsorption data were applied to pseudo-first-order and pseudo-second-order rate equations. The time data fitted well to pseudo second order kinetic model. According to the correlation coefficients, the adsorption of fluoride on the hydroxyapatite was correlated well with the Langmuir and Freundlich models

Interaction of adsorption of reactive yellow 4 from aqueous solutions onto synthesized calcium phosphate

The interaction of reactive yellow 4 with Apatitic Tricalcium Phosphate (PTCa) has been investigated in aqueous medium to understand the mechanism of adsorption and explore the potentiality of this phosphate toward controlling pollution resulting from textile dyes. Transmission electron microscopy (TEM) analysis demonstrates that the adsorbent is composed of needle-like nanoparticles and the SAED pattern exhibits spotted sharp and continuous rings that evidence polycrystalline grains. X-ray diffraction results showed that, the crystallinity of the dye decreased after interaction with RY4 indicatating incorporation of the dye into the micropores and macropores of the adsorbent. The results of Fourier transform infrared (FTIR) spectroscopy indicate that the adsorption is due to the electrostatic interaction between the –SO3- groups of dye and the surface of the Phosphate. The desorption efficiency was very high at about 99.4%. The presence of calcium ions favored the adsorption of the dye, while the phosphate ions inhibited it

The Numidian sand event in the Burdigalian foreland basin system of the Rif, Morocco, in a source-to-sink perspective

During the Tertiary evolution of the Western Mediterranean subduction system, a migrating foreland basin system developed between the Maghrebian orogenic belt and the adjacent African Craton. However, a comprehensive reconstruction of the foreland basin systems of the Rif Chain is still missing. By integrating field observations with quantitative biostratigraphic data from calcareous nannofossil assemblages, sandstone composition, and detrital zircon U-Pb geochronology from selected stratigraphic successions, we reconstruct the foreland basin system that developed in the early Miocene in front of the growing Rif orogen. The successions analyzed are representative of (1) the classical “Numidian Facies” from the Intrarifian Tanger Unit and (2) the Numidian-like deposits (mixed successions) of the “Mérinides Facies” from the “Maghrebian Flysch Basin” and the “Beliounis Facies” from the Predorsalian Unit. Our petrographic analyses and detrital zircon U-Pb ages show that the quartzarenites of the “Numidian Facies” originated from the African Craton, whereas the sublitharenites and feldspathic litharenites from the Mérinides and Beliounis Facies originated from a cratonic area and the exhuming Rif Chain. Our biostratigraphic analyses suggest a simultaneous arrival of the quartz grains in the Numidian, Mérinides, and Beliounis deposits, which indicates that their deposition occurred at ∼1 m.y. (ca. 20–19 Ma, early Burdigalian) and allows us to delineate the early Burdigalian foreland basin system of the Rif Chain. The foreland depozone received the “Numidian Facies,” the foredeep-hosted ~2000 m of the “Mérinides Facies” and the Beni Ider Flysch, whereas the wedge-top depozone was characterized by deposition of the “Beliounis Facies.” The Numidian Sandstones and the Numidian- like deposits analyzed in Morocco show the same age as similar deposits from Algeria, Tunisia, and Sicily, which suggests a comparable early Burdigalian tectono-sedimentary evolution along the southern branch of the Western Mediterranean subductionrelated orogen