Kinetic Studies of Zn(II) Removal from Single and Binary Solutions by Synthetic Hydroxyapatite - Based Nanopowders

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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.

mentioning

confidence: 99%

Hydroxyapatite Nanoparticles for Acidic Mine Waters Remediation

Simonescu¹,

Culiță²,

Marinescu³

et al. 2019

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“…As it is known, heavy metals are not biodegradable and they are bioaccumulated through all the levels of trophic chain having negative effects to all the living organisms [1]. Even at low level, almost all heavy metals are toxic to human beings [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The main anthropogenic sources of heavy metals are wastewater from industries such as: mining, plating, metal-finishing, electronic, metallurgical, fertilizers, synthetic chemicals, pulp and paper, pesticides, tanning, pigments, rubber and plastics, batteries and petroleum products [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…The different traditional remediation methods available for removal of toxic heavy metals from the water/wastewater include chemical precipitation, chemical coagulation and flocculation, electrochemical processes, ion exchange, membrane filtration, and adsorption [1,[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In the category of unconventional methods can be mentioned biosorption and bioremediation.…”

Section: Introductionmentioning

confidence: 99%

“…Zeolites are crystalline aluminum-silicates, with group I or II elements as counterions [20]. Their structure consists of a framework of [SiO4] 4 -and [AlO4] 5 -tetrahedra linked to each other at the corners by sharing their oxygen atoms [20]. The arranging of tetrahedra in the zeolite's structure leads to a threedimensional network with numerous voids and open spaces.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Zeolitic Materials Synthetized from Coal Fly Ash as Potential Cd(II) Adsorbents from Aqueous Solutions

Simonescu¹,

Melinescu²,

Culiță³

et al. 2020

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The aim of this research paper is to present a simple and efficient method to prepare zeolite materials from thermal power plant fly ash which is one of the most important waste resulted from power plants. The method of preparation of zeolite materials consists of alkaline activation followed by calcination at different temperatures. The zeolite materials prepared were studied by FT-IR spectroscopy, specific surface determination, X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM) and particle size composition. XRF data indicated that the zeolites synthesized are characterized by Si/Al ratio between 1.21 and 1.26, being mainly composed of Na-P1 zeolite. The optimum conditions of cadmium ions removal process by adsorption onto zeolite materials have been determined. It was concluded that increase of calcination temperature has as result increase of specific surface area and cosequently the increase of sorption capacity. An equilibrium, kinetic and thermodynamic study has been performed. The high value of correlation coefficient for the Langmuir isotherm reveals that the Cd(II) sorption onto zeolite materials occurs as a monolayer coverage of Cd(II) ions on homogenous zeolite surface. The pseudo-second-order kinetic model fits the experimental results of the Cd(II) sorption onto zeolite materials processes. As a results, the mechanism involved in Cd(II) sorption onto zeolite materials is based on chemical reactions. The thermodynamic results indicate that the Cd(II) adsorption process is more encouraging at higher temperatures.The results established that valuable NaP1 zeolite materials with high adsorption capacity can be prepared from thermal power plant fly ash through a simple method. The materials prepared can be utilized to remediate cadmium ions-bearing wastewater.

“…Due to their tendency to accumulate in organisms and cause diseases, their presence in the environment is not desirable. Different chemical treatments have been tried to avoid water pollution, such as chemical precipitation [13], chemical reduction [14], extraction [15], adsorption [16,17].…”

Section: Introductionmentioning

confidence: 99%

Optimization by Experimental Design of Copper Adsorption on Natural Clay

Stănăşel¹,

Bota²,

Stănăşel³

et al. 2020

Natural clay from the Felix geothermal area was used to assess the possible removal of heavy metals from wastewaters. Several experimental conditions, including pH, contact time and temperature, depending on the initial concentration were studied. The design of experiments method was applied in order to get the highest percentage of adsorbed copper. The factorial experiments were performed according to the matrix program developed by Design Expert. The obtained mathematical model assessed the optimal values of the factors that influence the adsorption of copper, taking into account maximum productivity, as well as economic criteria. The estimated values were in accordance with the experimental research.