Synthesis of Ca-Mg-Al layered double hydroxide from dolomite with ultrasound-assisted method. Application in phosphate removal

Vanessa Jurado-Davila,Ivo Andre H Schneider,Liliana Amaral Féris

doi:10.1016/j.inoche.2023.111829

Vanessa Jurado-Davila, Ivo Andre H Schneider + Show 1 more

Open Access

https://doi.org/10.1016/j.inoche.2023.111829

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Abstract

The aim of this work was to obtain a Layered Double Hydroxide (LDH) from natural dolomite and to apply the synthetized solid (CaMgAl-LDH) for phosphate removal by adsorption. Both the conventional coprecipitation method and ultrasound-assisted method were used to obtain CaMgAl-LDH. The obtained solids were characterized by N2 adsorption/desorption, size of pores, X-ray diffraction, and FTIR. Batch scale experiments were carried out to evaluate the phosphate adsorption capacity on CaMgAl-LDH using design of experiments (DOE). The studied parameters were pH, solid dosage, contact time and phosphate removal percentage, which was selected as the response function. Experimental data were fitted to kinetics and isotherms mathematical models. The process thermodynamics was also studied. Results showed that the ultrasound-assisted method was more efficient to obtain LDH even in a short period of sonication. The solids presented good crystallization, structure between layers, and high purity. Besides, LDH obtained by ultrasound exhibited a surface area of about 40% greater than the LDH obtained by the conventional method. The results of LDH application for phosphate removal showed high adsorption capacity (>94%) in several conditions of contact time and pH, even in low solid dosage. The kinetics of the process followed the pseudo-second-order model and Redlich-Peterson was the isotherm model that presented the best adjust. The thermodynamic parameters suggested a spontaneous, endothermic, and randomness process at the solid/solution interface, confirming an adsorption system favorable. The results exhibited that the ultrasound-assisted method is promissory to obtain LDH from mineral sources such as dolomite due to decrease energy expenditure and short synthesis time. It was found the ultrasound-assisted method also improve the solid physicochemical characteristics for its use in the adsorption process, enhancing the phosphate removal.

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