Marcos R. Mafra

Adsorption of remazol brilliant blue on an orange peel adsorbent

Abstract - A novel orange peel adsorbent developed from an agricultural waste material was characterised and utilised for the removal of Remazol Brilliant Blue from an artificial textile-dye effluent. The adsorption thermodynamics of this dye-adsorbent pair was studied in a series of equilibrium experiments. The time to reach equilibrium was 15 h for the concentration range of 30 mg L -1 to 250 mg L -1 . The adsorption capacity decreased with increasing temperature, from 9.7 mg L -1 at 20 °C to 5.0 mg L -1 at 60 °C. Both the Langmuir and Freundlich isotherm models fitted the adsorption data quite reasonably. The thermodynamic analysis of dye adsorption onto the orange peel adsorbent indicated its endothermic and spontaneous nature. Thus, the application of orange peel adsorbent for the removal of dye from a synthetic textile effluent was successfully demonstrated. Keywords : Orange peel; Adsorption; Dye; Kinetics; Thermodynamics; Wastewater. INTRODUCTION Wastewaters from the food colouring, paper, carpet, rubber, plastics, cosmetics and textile industries are polluted by dyes (Namasivayam

Adsorption of glycerol, monoglycerides and diglycerides present in biodiesel produced from soybean oil.

The most common methods currently used for the removal of waste glycerol, monoglycerides and diglycerides remaining after phase separation during biodiesel production involve wet processes. These procedures are not environmentally viable because they require large volumes of water and thus generate significant quantities of effluent. In this study, adsorption was employed to replace this purification step. Some commercial activated carbons were tested along with adsorbents chemically modified with HNO3. A kinetics study was conducted at 30°C and adsorption isotherms were obtained at 20°C, 30°C and 40°C. The results indicated that the adsorption of glycerol increased with the use of chemically-modified activated carbon, showing that pH has a strong influence on glycerol adsorption. The pseudo-first-order kinetic model provided the best fit with the experimental data for the monoglycerides while the pseudo-second-order model showed a better fit for the glycerol and diglycerides. The Freundlich model had the best fit with experimental data on the adsorption equilibrium for all temperatures. The thermodynamic study indicated that the adsorption process is endothermic and thus adsorption is favoured by increasing the temperature. The adsorption process using chemically-modified activated carbon was therefore very effective for the removal of waste glycerol resulting from biodiesel production, which is of considerable significance given the legal limits imposed.

Determination of heat-set gelation capacity of a quinoa protein isolate ( Chenopodium quinoa ) by dynamic oscillatory rheological analysis

This work aimed to study the influence of pH (3.5 and 7.0) and CaCl2 and MgCl2 addition on heat-set gelation of a quinoa protein isolate at 10% and 15% (w/w). The protein isolate obtained was composed mainly of 11S globulin as was observed by electrophoresis and mass spectrometry analysis. Heat-set gelation occurred at both pH values studied. Nevertheless, the gels formed at pH 3.5 were more viscoelastic and denser than those formed at pH 7.0, that was coarser and presented syneresis. The CaCl2 and MgCl2 addition increased the gel strength during rheological analysis at pH 3.5, possibly due to the formation of fiber-like connections in the gel network. At pH 7.0, the divalent salts resulted in weaker gels formed by agglomerates, suggesting a neutralization of the protein surface charges. The differences in quinoa protein gelation were attributed to solubility, and the flexibility of proteins secondary structure at the pH studied.

Modelling studies by adsorption for the removal of sunset yellow azo dye present in effluent from a soft drink plant

This paper reports a study on the adsorption of the dye sunset yellow, present in an aqueous synthetic solution and a real effluent from a soft drink plant, onto granular-activated carbon derived from coconut husks, using a batch system. The kinetic equilibrium was investigated using two different dye concentrations (102 and 103 mg L−1) at 25°C and 150 rpm. The adsorption isotherms and thermodynamics parameters were evaluated at 25°C, 35°C, 45°C and 55°C, using the synthetic and real effluents (5–103 mg L−1). Experimental data showed that the adsorbent was effective in the removal of sunset yellow dye and the contact time required to attain the adsorption equilibrium did not exceed 10 h. The adsorption capacity was not influenced within a wide range of pH values (1–12), although at high dye concentrations it increased with increasing temperature for both the synthetic and real effluents. The Redlich–Peterson isotherm best represented the equilibrium data of the system. The negative values obtained for Δ G0 and Δ H0 suggest that this adsorption process is spontaneous, favourable, and exothermic. The positive values for Δ S0 indicate an increase in the entropy at the solid/liquid interface. Based on the results of this study, adsorption appears to be a promising method for the removal of sunset yellow azo dye from effluent generated at soft drink plants.

Effect of heating and ionic strength on the interaction of bovine serum albumin and the antinutrients tannic and phytic acids, and its influence on in vitro protein digestibility

Bioavailability of food nutrients can be reduced in the presence of antinutrients such as phytates and tannins. This work aimed to study bovine serum albumin binding to phytic acid and tannic acid, and its influence on in vitro protein digestibility. The effect of autoclaving and boiling on protein digestibility and the microstructure of complexes was also evaluated. Results showed that high ionic strength promotes greater affinity between tannic acid and bovine serum albumin, and decreases in vitro protein digestibility. For phytic acid and bovine serum albumin, the opposite behavior is observed because interactions are governed by electrostatic forces. A rise in temperature above that causing denaturation of the protein favors its interaction with phytic acid, and disfavors that with tannic acid, probably due to different protein binding site exposure. For both antinutrients, heating treatment increased protein hydrolysis, the size of complexes and their fragility.

Assessment of Sodium Salt Anions (\(\text{SO}_{4}^{2-}\) and \(\text{NO}_{3}^{-}\)) Influence on Caffeine Partitioning in Polyethylene Glycol and 1-Butyl-3-Methylimidazolium Tetrafluoroborate Based ATPS

Liquid–liquid equilibrium (LLE) data of aqueous polyethylene glycol (PEG) + sodium salt and ionic liquid (IL) + sodium salt two-phase systems (ATPSs) were determined experimentally at 298.15 K and atmospheric pressure (91 kPa), applying PEG 1500, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), sodium sulfate (Na2SO4) and sodium nitrate (NaNO3) as phase-forming components. PEG and IL based ATPSs were applied for caffeine partitioning study and the influence of sodium salt anions (SO42-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Effect of tannic acid on the structure and activity of Kluyveromyces lactis β-galactosidase

\text{SO}_{4}^{2-}

Influence of Ternary Complexation between Bovine Serum Albumin, Sodium Phytate, and Divalent Salts on Turbidity and In Vitro Digestibility of Protein

\end{document} and NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}