Characterization of the Physical, Chemical, and Adsorption Properties of Coal-Fly-Ash–Hydroxyapatite Composites

Abstract

(1) Hydroxyapatite (Hap), which can be obtained by several methods, is known to be a good adsorbent. Coal fly ash (CFA) is a commonly reused byproduct also used in environmental applications as an adsorbent. We sought to answer the following question: Can CFA be included in the method of Hap wet synthesis to produce a composite capable of adsorbing both heavy metals and dyes? (2) High calcium lignite CFA from the thermal power plant in Bełchatów (Poland) was used as the base to prepare CFA–Hap composites. Four types designated CFA–Hap1–4 were synthesized via the wet method of in situ precipitation. The synthesis conditions differed in terms of the calcium reactants used, pH, and temperature. We also investigated the equilibrium adsorption of Cu(II) and rhodamine B (RB) on CFA–Hap1–4. The data were fitted using the Langmuir, Freundlich, and Redlich–Peterson models and validated using R2 and χ2/DoF. Surface changes in CFA–Hap2 following Cu(II) and RB adsorption were assessed using SEM, SE, and FT-IR analysis. (3) The obtained composites contained hydroxyapatite (Ca/P 1.67) and aluminosilicates. The mode of Cu(II) and RB adsorption could be explained by the Redlich–Peterson model. The CFA–Hap2 obtained using CFA, Ca(NO3)2, and (NH4)2HPO4 at RT and pH 11 exhibited the highest maximal adsorption capacity: 73.6 mg Cu/g and 87.0 mg RB/g. (4) The clear advantage of chemisorption over physisorption was indicated by the Cu(II)–CFA–Hap system. The RB molecules present in the form of uncharged lactone were favorably adsorbed even on strongly deprotonated CFA–Hap surfaces.

Characteristics of the Properties of Absodan Plus Sorbent and Its Ability to Remove Phosphates and Chromates from Aqueous Solutions

“…Compressed adsorbent samples were mixed with KBr at a constant adsorbent weight to KBr weight ratio of 0.25% and pelleted under pressure. The FTIR spectra were employed in a spectral range of 4000 to 500 cm −1 [ 58 ]. Determination of point of zero charge (PZC) of diatomite: The PZC was determined using three methods: Suspension method: In a series of 250-mL Erlenmeyer flasks, 0.5 g of diatomite was added to 50.0 mL of 0.1 M NaNO 3 solution.…”

“…Compressed adsorbent samples were mixed with KBr at a constant adsorbent weight to KBr weight ratio of 0.25% and pelleted under pressure. The FTIR spectra were employed in a spectral range of 4000 to 500 cm −1 [ 58 ].…”

Biochar supported metallo-inorganic nanocomposite: A green approach for decontamination of heavy metals from water

“…The adsorption kinetics were further investigated to identify the rate-controlling steps occurring during the adsorption process by using the intra-particle diffusion model [43], which is represented by Eq (10).…”

“…The materials like Coal fly ash modified hydroxyapatite, iron doped Ethiopian nano clay, Hydrocalcite/hydroxyapatite impregnated carbon nanotubes, magnetic nanoparticles modified chitosan incorporated biochar, iron nanoparticles impregnated tea waste, magnetic nanoparticles decorated tea waste biochar, etc. have been employed for removal of multiple heavy metals (Cu(II), Ni(II), Cr(VI)) with uptake capacities ranging from 11.97-200.80 mg g -1 , but consumed prolonged time (2-72 hours) to reach equilibrium stage [8][9][10][11][12][13] (S1 Table ). Among these multifarious adsorbents, biochar-based ones have attracted much more attention owing to their low cost and easy availability of the raw materials especially if they are waste-derived.…”

Experimental Studies on the Removal of Textile Dye of Naphthol Green B from Artificially Contaminated Water Using Purolite MB400 Ion Exchange Resin

“…Adsorption has emerged as one of the most promising technique due to its versatility and simplicity (Sočo 2021). The advantages of adsorption process include low cost, simplicity of operation and the capability to treat dye effluent even at high concentrations (Ardila-Leal 2021).…”