Characterization of Brazilian palygorskite (Guadalupe region) and adsorptive behaviour for solvatochromic dyes

Abstract

This work presents the results of the physical characterization of palygorskite and its adsorptive behaviour for three solvatochromic dyes (Nile blue chloride (NBC), methylene blue (MTB) and dithizone (DTZ)). Adsorption isotherms were used to determine the maximum adsorption of the solvatochromic dyes on the palygorskite. The characterization of palygorskite was carried out via mineralogical and chemical analysis with X-ray diffraction, X-ray fluorescence, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, surface-charge measurement (ζ-potential), thermogravimetric analysis, textural analysis and cation-exchange capacity analysis. The material consists of palygorskite and quartz and its chemistry is dominated by SiO2, MgO and Fe2O3. The specific surface area and cation-exchange capacity of the palygorskite are 142 m2 g–1 and 41 cmol(+) kg–1, respectively. The SEM and TEM analyses showed a fibrous structure with fibres 20–100 nm long. The thermogravimetric analysis showed three endothermic events at 57.3°C, 171.8°C and 439.6°C. The adsorption capacities of the palygorskite for NBC (basic pH), MTB (basic pH) and DTZ (neutral pH) were 0.082, 0.013 and 0.102 g g–1, respectively. The adsorptions of NBC and MTB were fitted with the Langmuir isotherm model and the adsorption of DTZ was fitted with the Sips model.

Removal of Fe3+ Ions from Aqueous Solutions by Adsorption on Natural Eco-Friendly Brazilian Palygorskites

“…Paly deposits around the world mostly come from arid or semiarid regions [21]. In Brazil, these deposits are mainly located in the municipality of Guadalupe, Piaui state (see Figure 1), and were discovered in 1982 [22][23][24][25][26][27]. Paly has been used in domestic water purification, drilling fluids, cosmetics, pharmaceuticals and polymer formulations [28][29][30][31][32][33][34][35][36], including to remove cations by adsorption [37][38][39][40].…”

Adsorption Behavior of Crystal Violet and Congo Red Dyes on Heat-Treated Brazilian Palygorskite: Kinetic, Isothermal and Thermodynamic Studies

“…Clays are often used as adsorbents for economic feasibility and environmental importance due to their low cost, abundance, immediate availability, non-toxicity and high adsorptive properties [49][50][51]. Due to its fibrous structure and high surface area, the palygorskite clay has gained considerable prominence as an adsorbent to remove various types of pollutants [44,45,[52][53][54][55][56].…”