Diego de Quadros Melo

Treatment influence on green coconut shells for removal of metal ions: pilot-scale fixed-bed column

This work investigates copper, nickel and zinc ion biosorption in single- and multi-component systems in a fixed-bed column using green coconut shells (CS). Approximately 85% of biosorbents are in a particle size ranging from 0.25 to 2 mm. Operational parameters selected include a flow rate of 200 mL min−1 and a bed height of 100 cm, which were selected for a shorter execution time and good adsorption capacity. Empty-bed contact time and Thomas models were applied, showing a good fit with the experimental data. The column adsorption capacity increased after the green CS powder was treated in a column with NaOH at a concentration of 0.1 mol L−1. The highest values of adsorption capacities founded were 0.69, 0.45 and 0.39 mmol L−1 for Cu(II), Ni(II) and Zn(II), respectively, using green CS treated inside a column with NaOH of 0.1 M. The pH and chemical oxygen demand were monitored in the treatment solution and indicated that the adjustment of these parameters is necessary before disposal of these solutions. A study of desorption using an acid solution was carried out for recovery of metal ions.

Biosorption of metal ions using a low cost modified adsorbent (Mauritia flexuosa): experimental design and mathematical modeling

ABSTRACT Buriti fibers were subjected to an alkaline pre-treatment and tested as an adsorbent to investigate the adsorption of copper, cadmium, lead and nickel in mono- and multi-element aqueous solutions, the results showed an increase in the adsorption capacity compared to the unmodified Buriti fiber. The effects of pH, adsorbent mass, agitation rate and initial metal ions concentration on the efficiency of the adsorption process were studied using a fractional 24−1 factorial design, and the results showed that all four parameters influenced metal adsorption differently. Fourier transform infrared spectrometry and X-ray fluorescence analysis were used to identify the groups that participated in the adsorption process and suggest its mechanisms and they indicated the probable mechanisms involved in the adsorption process are mainly ion exchange. Kinetic and thermodynamic equilibrium parameters were determined. The adsorption kinetics were adjusted to the homogeneous diffusion model. The adsorption equilibrium was reached in 30 min for Cu2+ and Pb2+, 20 min for Ni2+ and instantaneously for Cd2+. The results showed a significant difference was found in the competitiveness for the adsorption sites. A mathematical model was used to simulate the breakthrough curves in multi-element column adsorption considering the influences of external mass transfer and intraparticle diffusion resistance.

Multielement adsorption of metal ions using Tururi fibers (Manicaria Saccifera): experiments, mathematical modeling and numerical simulation

AbstractA numerical and experimental study of the multielement adsorption of Cd2+, Cu2+, Ni2+, and Pb2+ metal ions in batch and column system were carried out in aqueous solution using Tururi fibers as adsorbent. The kinetics and thermodynamic equilibrium parameters were studied. The adsorption kinetics was fitted to the homogeneous diffusion model and the results showed good linear correlation coefficients. Furthermore, a mathematical model was built to describe the mass transfer kinetics for fixed bed column tests. The effects of constant adsorption equilibrium, external mass transfer, and intraparticle diffusion resistance on breakthrough curves were studied. The equations which describe the phenomenology were discretized using the finite volumes method with the weight upstream differencing scheme and central difference scheme formulations. The results for the breakthrough curves obtained through simulation showed good agreement compared with the experimental data.

Adsorption of Safranin on Pseudostem Banana Fibers

Adsorption assays indicated that the pseudostem banana fibers are an efficient sorbent for the removal of safranin from aqueous solution being dependent on pH, dye concentration, and temperature. Kinetics and thermodynamic studies indicated Sips isotherm as the most suitable model to describe the studied adsorption process, which occurs through a pseudo second-order process. The thermodynamic parameters indicated that the sorption of safranin dye onto pseudostem banana fiber is spontaneous (ΔGads ≅ –30 kJ mol−1) and exothermic (ΔHads ≅ –17 kJ mol−1).

Chemometric Characterization of Alembic and Industrial Sugar Cane Spirits from Cape Verde and Ceará, Brazil

Sugar cane spirits are some of the most popular alcoholic beverages consumed in Cape Verde. The sugar cane spirit industry in Cape Verde is based mainly on archaic practices that operate without supervision and without efficient control of the production process. The objective of this work was to evaluate samples of industrial and alembic sugar cane spirits from Cape Verde and Ceará, Brazil using principal component analysis. Thirty-two samples of spirits were analyzed, twenty from regions of the islands of Cape Verde and twelve from Ceará, Brazil. Of the samples obtained from Ceará, Brazil seven are alembic and five are industrial spirits. The components analyzed in these studies included the following: volatile organic compounds (n-propanol, isobutanol, isoamylic, higher alcohols, alcoholic grade, acetaldehyde, acetic acid, acetate); copper; and sulfates.

Allergenic Fragrances Analysis in Brazilian Perfumes by Headspace Solid Phase Microextraction and Gas Chromatography-Mass Detector (HS-SPME-GC-MS)

Perfumes are products mainly consisting of ethyl alcohol, water and fragrance. These fragrances are responsible for characterizing the pleasant and unique odor of each perfume. Among the fragrances, we highlight a group of fragrances which can cause contact allergy, leading to dermatitis. Brazilian and the European law state that when these concentrations of allergenic fragrances exceed the limit of 0.01% for non-rinse products and 0.001% for products with rinsing, the manufacturer is obliged to discriminate on its label their presence. This work aims to quantify allergic fragrances in original and Brazilian perfume using solid-phase microextraction and analyze by gas chromatography-mass detector.

Hybrid polymers composite: Effect of hybridization on the some propers of the materials

Abstract In recent years, ecological awareness and other environmental issues led to the development of composite materials based on renewable resources. These materials are environment-friendly and low-cost alternatives to replace synthetic fibers like glass and carbon fibers. Composite materials are heterogeneous mixtures of two or more homogeneous phases with properties that could not have been obtained separately. The polymeric matrix materials with suitable and proper filler, better filler/matrix interaction together with advanced and new methods or approaches are able to develop polymeric composites with great prospective applications in constructions and buildings, automotive, aerospace, and packaging industries. In this context, hybrid bio-based composites that exploit the synergy between natural fibers in a nano-reinforced bio-based polymer can lead to improved properties along with maintaining environmental appeal. This chapter will present some properties of the above-mentioned eco-friendly and bio-degradable hybrid polymer composites and the best possible applications of this kind of materials.