Luciana Igarashi-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.

Degradation of an Azo Dye (Ponceau 4R) and Treatment of Wastewater from a Food Industry by Ozonation

Experiments for degradation of the extensively marketed Ponceau 4R dye in aqueous solution and for oxidation of raw wastewater from a confectionary industry have been carried out by using ozone. All the experiments were performed in a cylindrical semi-batch reactor at approximately 20 oC for 7200 s. A mass flow rate of 1.158 × 10−6 kg s−1 of ozone was continuously fed in the reactor. The pH of the azo dye aqueous solution (distilled water + Ponceau 4R) was always kept at approximately 5.8, while in the case of the raw wastewater the same factor was changed from 4.7 to 9.4 in two different experimental runs. Absorbance measurements at 508 nm show that the investigated azo dye found in the azo dye aqueous solution was completely degraded after only 600 s. At this initial period a substantial fall of TOC (Total Organic Carbon) (up to 45%) was noticed, but the rate was exponentially decreased at longer reaction times up to a TOC removal no higher than 60%. The ozonation was also responsible for reducing the apparent color of the raw wastewater to almost 10% of its initial value at the optimum pH (9.4 ± 1.5). The effect of pH was important on apparent color, but it had absolutely no influence on the kinetics results of COD (Chemical Oxygen Demand), which were kept constant over the entire period of reaction.

A comparative approach of methylparaben photocatalytic degradation assisted by UV-C, UV-A and Vis radiations

ABSTRACT Due to the widespread use of methylparaben (MEP) and its high chemical stability, it can be found in wastewater treatment plants and can act as an endocrine disrupting compound. In this study, the photocatalytic degradation and mineralization of MEP solutions were evaluated under UV-A, UV-C and Vis radiations in the presence of the photocatalyst TiO2. In this sense, the effects of the catalyst load, pH and MEP initial concentration were studied. Remarkably higher reaction rates and total photodegradation were achieved in systems assisted by UV-C radiation. The complete degradation was achieved after 60 min of reaction using the MEP concentration of 30 mg L−1 at pH 9 and 500 mg L−1 TiO2. The experimental data apparently followed a Langmuir-Hinshelwood kinetic model, which could predict 88–98% of the reaction behavior. For the best photodegradation condition, the model predicted an apparent reaction rate constant (kapp) equal to 0.0505 min−1 and an initial reaction rate of 1.5641 mg (L min)−1. Mineralization analyses showed high removal for MEP and derived compounds from the initial solution when using UV-C after 90 min of reaction. The lower toxicity was also confirmed by in vivo tests using MEP solutions previously treated by photocatalysis. GRAPHICAL ABSTRACT

Degradation of Odontologic X-Ray Film Developing Wastewaters by Photo-Fenton Process

Effluents from radiographic X-ray film developing processes feature a high contaminant load (COD about 70000 mg/L and total phenols concentration about 16956 mg/L). Photo-Fentons are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence of light to generate hydroxyl radicals (·OH). The photo-Fenton process was explored as a photochemical treatment to degrade wastewater from radiographic X-ray film developing processes coming from odontologic clinics. A response surface methodology was applied to optimize the photo-Fenton oxidation process conditions using total phenol removal as the target parameter to be optimized, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and time and pH as the control factors to be optimized. The best results in terms of maximal total phenol removal and economic process were achieved when wastewater samples were treated at pH 5 in the presence of hydrogen peroxide and iron in the ratios [total phenols]:[H2O2] 1:3 w/w and [Fe2+]:[H2O2] 1:18 w/w and time 1 h.

Effects of freezing and the cryoprotectant lactobionic acid in the structure of GlnK protein evaluated by circular dichroism (CD) and isothermal titration calorimetry (ITC)

Freezing is a widely applied method in food preservation. The technique has negative effects on sensory and textural properties of some foods. In this study the effects of the freeze–thaw process and lactobionic acid (LBA) as a cryoprotectant on GlnK protein solution were evaluated by circular dichroism (CD) analysis and isothermal titration calorimetry (ITC). The freeze–thaw cycles caused changes in GlnK conformation and interactions with small ligands (adenosine triphosphate, ATP). CD assay demonstrated changes in the molar ellipticity values of the samples subjected to freezing, indicating conformational changes to the GlnK protein. Additionally, ITC analysis indicated that the freeze–thaw process caused changes in the interaction properties of GlnK with its ligand ATP. LBA cryoprotectant activity was also evaluated and with both of the techniques it was demonstrated that the compound prevented the damage caused by the freeze–thaw process, thereby maintaining the characteristics of the samples.

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

Tannins are compounds with antinutrient properties that hinder food digestibility, prejudicing human and animal nutrition. This work aimed to evaluate the negative effects of tannic acid on Kluyveromyces lactis β-galactosidase catalytic activity and correlate these changes with the protein structure. β-Galactosidase activity decreased in the presence of tannins, which caused changes to the structure of the enzyme, as demonstrated by circular dichroism. It was verified that tannin binds to the protein by a static mechanism. Additionally, isothermal titration calorimetry suggested that tannic acid modified the molecular interaction between β-galactosidase and o-nitrophenyl-β-d-galactoside, reducing their affinity and prejudicing the protein activity. This study helps to understand the effects of tannins on the β-galactosidase structure and how they are related to the enzyme catalytic activity. The alterations in the conformation and activity of the enzyme should be taken into consideration when dairy products are consumed with tannin-rich food.

Application of Response Surface Methodology for Coffee Effluent Treatment by Ozone and Combined Ozone/UV

ABSTRACT This paper reports a study using ozone (O3) and combined ozone/ultraviolet (O3/UV) processes for color removal and caffeine degradation from synthetic coffee wastewater using a second-order response surface methodology (RSM) with a three-level central composite face-centered (CCF) design. The effects of O3 concentration, initial pH, and reaction time were examined for both processes. The reaction time and pH were statistically significant for caffeine degradation and color removal. In the ozonation process, higher caffeine degradation and color removal were observed in alkaline pH, indicating that ozone attacks indirectly, consequently generating hydroxyl radicals. Regarding the ozone/UV process, it was observed that lower caffeine degradation and color removal occurred at neutral pH, indicating an adverse effect due to lower ozone dissolution and consequently the production of a smaller amount of free hydroxyl radicals. The achieved results showed that the techniques were efficient for color removal (85% and 99%, respectively) and caffeine degradation (88% and 98%, respectively).