Abstract
CaCr LDH materials were synthesized by the co-precipitation method, using Gastropod shell as a biogenic source of Ca2+. The mineralogical, surficial morphology and elemental composition analysis of the materials showed characteristics typical of hydrotalcite-like materials, composed of Ca, Cr, O, C and Cl. Batch equilibrium adsorption studies showed that phosphate sorption on the LDH reached equilibrium within 5 min with about 98% removal. The sorption of phosphate was well described by the Langmuir isotherm model. The monolayer adsorption capacity of the CaCr LDH for phosphate was 142.86 mg/g. Mechanistic studies of phosphate removal by the LDHs was elucidated via instrumental analysis, vis-a viz, SEM-EDX, XRD and FTIR. Results revealed that phosphate was removed via the combination of ion exchange and precipitation. It could be inferred that CaCr LDH synthesised using Gastropod shell as a biogenic source of Ca2+ is a suitable adsorbent for phosphate removal from aqua system.
Highlights
Layered double hydroxides (LDH) are laminar anionic clay materials known as hydrotalcite compounds and characterized with high exchange capacity [1]
CaCr LDH synthesised using Gastropods shell as Ca2+ source was evaluated for phosphate removal from a synthetic feed phosphate wastewater in a
The dissolution phenomenon of the LDHs is responsible for the lost of the layered structure after phosphate uptake (Figure 20). These findings are in conformity with the removal of Ca-based LDHs for removing different P species in other previous studies [11, 25,26,27,28]. These findings reveal that the dual combinations of ion exchange and precipitation were the mechanisms of phosphate removal by the LDH sample
Summary
Layered double hydroxides (LDH) are laminar anionic clay materials known as hydrotalcite compounds and characterized with high exchange capacity [1]. The M1−x2+ Mx3+ (OH) represents the layer, while (An)x/n·mH2O represents the interlayer composition. Varying the M2+/M3+ ratio alters the charge density and the anion exchange capacity of the LDHs [2]. M is the amount of water in moles, present in the LDH. M2+, M3+, x, and Anidentities may vary over a wide range, giving rise to a large class of isostructural materials with different physicochemical properties [5,6]. Due to the high ionexchange properties of the interlayer anions, LDHs have attracted high research interests as promising materials for the selective uptake of polyatomic anions including phosphate from aqueous system [8]. CaCr LDH synthesised using Gastropods shell (a biogenic precursor) as Ca2+ source was evaluated for phosphate removal from a synthetic feed phosphate wastewater in a
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