Facile synthesis and characterisation of novel Sn/Si mixtures for the efficient removal of methylene blue and crystal violet dyes from aqueous media

In this work, novel mixtures based on silicon and tin materials were synthesised via reaction of 2.407, 5.247, 7.195, or 9.59 g of tin chloride dihydrate with 6 g of sodium metasilicate pentahydrate. The samples, which were synthesised using 2.407, 5.247, 7.195, and 9.59 g, are abbreviated as T1, T2, T3, and T4, respectively. XRD confirmed that these mixtures consist of amorphous Sn/Si, sodium tin silicate, tin oxide, and sodium silicate. The average crystallite size of T1, T2, T3, and T4 samples is 5.23, 8.13, 12.26, 15.72 nm, respectively. The synthesised mixtures were used as adsorbents for the removal of methylene blue and crystal violet dyes from aqueous media. 15 min, pH 6, and 298 Kelvin are regarded as the optimum conditions for the removal of studied dyes using T1, T2, T3, and T4 samples. The adsorption process of crystal violet or methylene blue dyes was fitted well with the Langmuir equilibrium isotherm and pseudo-second-order kinetic model. The thermodynamic parameters confirmed that the removal of crystal violet and methylene blue dyes is chemical, spontaneous, and exothermic. The maximum adsorption capacity of T1, T2, T3, and T4 samples towards crystal violet dye is 34.81, 36.83, 29.46, and 11.98 mg/g, respectively. Also, the maximum adsorption capacity of T1, T2, T3, and T4 samples towards methylene blue dye is 30.13, 29.33, 17.09, and 13.43 mg/g, respectively. HCl: butanol (1:3) can efficiently desorb the dyes for three cycles of adsorption/desorption. Hence, the adsorbents can be used successfully several times for the removal of crystal violet and methylene blue dyes.