Nanoscale composites of hydroxyapatite coated with zero valent iron: preparation, characterization and uranium removal

Eco-friendly hydroxyapatite and emerging MXenes for uranium adsorptive uptake

“…13 Zeng et al also found that one of the adsorption mechanisms between U( vi ) and HAP–ZVI was ion exchange. 52 Similarly, the higher than expected effluent Ca concentrations observed in the experiment by Lammers et al were likely ascribed to ion exchange of UO 2 2+ for Ca 2+ among incongruent dissolution of a metastable form of hydroxyapatite (mHAP) to produce chernikovite. 41 Interestingly, the pH and bicarbonate concentrations of solutions can influence ion exchange of uranium onto HAP.…”

“…U(VI) adsorption onto HAP-ZVI and PAAm-HAP was also found to be an endothermic and spontaneous process. 52,55 2.2.3. Influence of adsorption time and kinetic analysis of HAP-based materials.…”

“…13 Zeng et al also found that one of the adsorption mechanisms between U(VI) and HAP-ZVI was ion exchange. 52…”

“…U( vi ) adsorption onto HAP–ZVI and PAAm-HAP was also found to be an endothermic and spontaneous process. 52,55…”

Removal of Aqueous Uranyl and Arsenate Mixtures after Reaction with Limestone, PO43–, and Ca2+

“…Apatite minerals are found in igneous rocks such as pegmatites, and the natural formation of HAp is more commonly observed through biological pathways . Chemical precipitation can also be used to synthesize HAp, but the structural Ca and P stoichiometry and byproducts such as dicalcium phosphate dihydrate (brushite, CaHPO 4 ·2H 2 O) and octacalcium phosphate (Ca 8 H 2 (PO 4 )­6·5H 2 O) are influenced by solution pH, temperature, and reaction rates. , HAp has been applied in the removal of both U and As through mechanisms such as electrostatic attraction and dissolution–precipitation. − Other studies have reported HAp coatings were utilized to enhance the reactivity of activated carbon, , minerals, − polymeric materials, and biotic materials − for removal reactions. However, further investigations are necessary to identify the key adsorption and precipitation removal mechanisms under both acidic and neutral pH conditions for U and As mixtures using natural limestone with additions of Ca 2+ and PO 4 3 .…”