High performance on the moisture reduction in waste oils by a bentonite-based adsorption process.

In this work, the reduction of the moisture content from waste oils by a bentonite-based adsorption process was investigated as an alternative for reuse in energy production. Waste cooking oil (WCO) and waste poultry fat (WPF) were characterised (moisture and viscosity, values of acidity, saponification, and peroxide), as well as bentonite clay adsorbent. The response surface methodology (RSM) was applied to define the best moisture adsorption condition by bentonite-based adsorbent regarding a full factorial experimental design (FFED). In the framework of RSM, the adsorbent mass, oil acidity, and agitation speed were varied in three levels in the range of 1.5-3.0 g, 1-38 mgKOH goil-1, and 50-150 rpm, respectively, while the adsorption time was fixed in 24 h. Under the best moisture adsorption condition, kinetic tests were performed in a 1-24 h contact time range, besides performing equilibrium adsorption tests at 5 h contact time. Around 90% moisture removal was attained with 1.5 g adsorbent, acidity value of 1 mgKOH goil-1, and 50 rpm agitation speed, achieving the equilibrium in 5 h. A multilayer adsorption process, as described by the BET isotherm model, was acting in dried bentonite clay, allowing getting excellent moisture adsorption capacity (∼200 mgwater gBent-1). Therefore, moisture removal from waste oils by a bentonite clay-based adsorption process has provided results that are suitable and recommendable for economically viable biodiesel production.

Use of bentonite calcined clay as an adsorbent: equilibrium and thermodynamic study of Rhodamine B adsorption in aqueous solution.

The Rhodamine B adsorption was realized in batch using calcined bentonite clay. The effects of Rhodamine B initial concentration, pH, and temperature were evaluated and the conditions where the adsorption was favored were in 500 mg L-1, pH 3, and 35 °C. The equilibrium isotherms studied were from Langmuir and Freundlich. The coefficients of determination (R2 > 0.99) were found to confirm the best fitted to Langmuir isotherm, with a monolayer adsorption capacity (qmax) of 552.49 mg g-1. The kinetic data agreed well with the pseudo-second order model (R2 > 0.99). The in natura and calcined clay were characterized by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 physisorption (BET), and scanning electron microscopy (SEM). Thermodynamic parameters including Gibbs free energy (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were calculated to estimate the nature of Rhodamine B adsorption in clay. The results suggested that the adsorption was endothermic and spontaneous, with the enthalpy adsorption increasing with the increase of temperature. Therefore, calcined bentonite can be used as an efficient adsorbent for discoloration of large volume of residual water, presenting low-cost and high adsorptive capacity.

Synthesis and spectroscopic analysis of polydiphenylamine via oxidation with bentonite clay in the solid state.

In this study, solids of polydiphenylamine (PDPA) synthesized mechanochemically by reaction with bentonite (PDPAOB) were studied using Raman spectroscopy. It was possible to identify the chemical species in the PDPA-bentonite compound. The spectra obtained were compared to the spectra of PDPA prepared chemically by oxidation of DPA with K2S2O8 in the solid state, and PDPA produced electrochemically, with the aim of studying the characteristic frequencies of the aromatic segments (DPB), radical cation (DPB(+)) and dication (DPB(2+)) of N,N-diphenylbenzidine (DPB) in the polymer structure of the PDPA. To analyze the segments present, the band characteristic of CC asymmetric stretching of the aromatic ring in the Raman spectra was deconvoluted because of the widening of the band and shifts observed by irradiation at wavelengths of 532 and 785 nm. This procedure showed that there are three distinct contributions in the spectra which facilitate the monitoring of changes in the contributions of the segments in the materials doped with HCl (PDPAOBD) and de-doped with NH4OH, (PDPAOBR).

Polyamide 6 Nanocomposites with Inorganic Particles Modified with Three Quaternary Ammonium Salts.

The purpose of this study was to obtain polyamide 6 nanocomposites with national organically modified clay with three quaternary ammonium salts. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or partially exfoliated structures. The nanocomposites showed similar thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results.