Facile Synthesis of β-SrHPO₄ with Wide Applications in the Effective Removal of Pb²⁺ and Methyl Blue

Abstract

A facile synthesis routine of β-type strontium hydrogen phosphate (β-SrHPO4) nanosheets was provided by the method of solution growing at temperatures below 80 °C. β-SrHPO4 was utilized for removing lead ions (Pb2+) and adsorbing methyl blue. Within the pH values from 2.0 to 6.0 of lead solutions, the adsorption capacity of β-SrHPO4 could reach above 1000 mg·g–1. The maximum removal capacity was 1409 mg·g–1 for Pb2+ within 15 min at pH = 4.5 and remained stable with the increase of temperatures. Different cations (Zn2+, Cr3+, Cd2+, and Co2+) affected slightly on the adsorption of Pb2+. It is revealed that the adsorption mechanism of Pb2+ was based on dissolution–precipitation theory. The maximum adsorption capacity was 335.68 mg·g–1 for methyl blue. The adsorption data of methyl blue accorded with the Langmuir isotherm model with R 2 = 0.994 and the pseudo-second-order kinetic model with R 2 = 0.99996, showing that the removal of methyl blue was dominated by a chemical sorption process. The thermodynamic studies demonstrated that the adsorption process toward methyl blue was endothermic and spontaneous. All of the results showed that β-SrHPO4 possessed potential applications in removing Pb2+ and methyl blue.

Graphene Oxide-Based Fe–Mg (Hydr)oxide Nanocomposite as Heavy Metals Adsorbent

“…To study the effect of temperature on the adsorption process, the thermodynamic parameters, Gibbs energy (ΔG), entropy (ΔS), and enthalpy (ΔH) were calculated from eqs 9 and 10. 49,50 (10) where R is the gas constant (8.314 J/mol•k), T (K) is the absolute temperature, and K c is the equilibrium partition coefficient and can be calculated from eq 11. 49,50…”

“…The positive values of ΔH implied that the adsorption process was endothermic. 49,50 3.6. Adsorption Mechanism.…”

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