Hydroxyapatite Nanoparticles for Acidic Mine Waters Remediation

Abstract

Mining activities have a high negative impact on the environment and on human health. Environmental impacts can result in contamination of surface water, groundwater, soil and air. Large volumes of wastewater produced by mining activities have to be remediated before being discharged into the environment. Due to the complex composition of wastewater coming from the mining industry and because their negative impacts, numerous remediation techniques have been applied. Adsorption is one of the most extensively used ways to remediate mining wastewater as a consequence of its low cost, easiness to be performed, and also due to the wide variety of materials (natural and synthetic) that can be use as adsorbents. Hydroxyapatite (HAP, Ca10(PO4)6(OH)2), a naturally occurring form of calcium phosphate has a good capacity to remove heavy metal ions from aqueous solutions due to its excellent properties. By preparing hydroxyapatite using different synthesis methods, its properties can be manipulated in order to increase the adsorption properties and reactivity. Herein, we reported synthesis of hydroxyapatite (HAP) samples using different synthesis conditions to establish the effect of synthesis conditions onto HAP properties. The HAP samples prepared have been characterized by the use of X-ray diffraction, FT-IR spectroscopy, specific surface measurements, Scanning Electron Microscopy (SEM). The stoichiometric compounds with high degree of crystallinity, low average particle diameter values, and low specific surface have been prepared by the solid state reaction and high calcination temepratures. The addition of surfactant (dispersant) has resulted in an increase in the specific surface area, which will result in an increase in the retention capacity of heavy metal ions in wastewater. The adsorbents prepared were used to remediate mine water. Results showed that non-calcinated HAP samples have a higher heavy metals adsorption capacity compared to HAP samples calcinated at 600 �C and 900 �C. The HAP samples prepared in presence of surfactant exhibit a higher heavy metals adsorption capacity than samples prepared in absence of surfactant. The values of the retention capacity differ depending on the nature of the metal ion: QMn(II) ] QFe(III) ] QZn(II) ] QPb(II) ] QNi(II). A change in the pH of mine water from 2.6 to 5.5 has occur that means that the metal ion retention mechanism goes through chemical reactions. The metal ions retention capacity suggests application of hydroxyapatite for remediation of mining wastewater.

Pharmaceutical Applications of Chitosan Extracted from Local Marine Sources

“…The vibrations registered at 1638 cm -1 , 1633 cm -1 and 1606 cm -1 are assigned to NH 2 -bending (amino groups) specific to chitosan structure from the three samples [13,14]. It can be observed that the specific peaks of chitosan are found at the specified wavenumbers for all the three analyzed samples, which confirms its structure.…”

Competitive Adsorption of Aqueous Cd(II) and Pb(II) Solutions onto Silicas Synthesized with Saponin as Template Agent

“…Numerous studies have been carried out on the remediation of Pb(II) and Cd(II) ions in industrial effluents and aqueous solutions by adsorption. The following adsorbent materials have been used: activated carbon and its derivatives [6], clays [7], natural and synthetic zeolites [8,9], hydroxyapatite and its composites [10], hydroxides [11], carbon nanotubes [12], simple and small oxides [13,14], silicates and their derivatives [15,16], magnetic nanoparticles [17][18][19], lignin and its derivatives [20], chitosan-based materials [21], geopolymers [22], metal-organic compounds [23], food waste [24], agricultural waste [25], industrial waste [26]. Among these, porous materials are considered alternative adsorbents with improved adsorption performance compared to activated carbon and other conventional adsorbent materials.…”

Electrodeposited MnO2-based Capacitive Composite Electrodes for Pb2+ Adsorption

“…A large amount of wastewater containing Pb 2+ is inevitably produced from non-ferrous metal mining and smelting [1][2][3], lead-acid batteries [4,5] and other chemical production processes [6]. Because of its non-degradability and the enrichment in natural circulation systems Pb 2+ may cause serious harm to humans, animals and plants [7,8].…”