Croton argyrophylloides Muell. Arg. is widely used in Brazilian folk medicine to treat diabetes and venereal diseases. This study examined the acute toxicity and cytotoxicity of the essential oil of C. argyrophylloides (EOCA). In addition, vascular effects of the EOCA have been examined. In mice, an oral acute toxicity test revealed that EOCA could be considered as a non toxic essential oil since it showed a very high LD 50 (9.84 ± 0.01 g/kg). In the brine shrimp (Artemia salina) cytotoxic assay, the LC 50 value of EOCA was 275 [165-534] µg/mL. EOCA (1-1000 µg/mL) relaxed isolated endothelium-intact aortic rings precontracted with phenylephrine with an IC 50 value of 126.7 [89.8-163.7] µg/mL. In rat mesenteric bed preparations precontracted with phenylephrine, EOCA (1-300 µg/mL) also induced a reversible, vasodilator effect with an IC 50 value of 46.0 [33.3-58.7] µg/mL. It is concluded that EOCA is a very interesting agent from the point of view of the possibility of therapeutic application. This is because, whilst showing a very small acute toxicity, EOCA also showed maximal efficacy as a vascular antispasmodic agent with a pharmacological potency similar to that of other Croton species essential oils.

This work investigates the removal of Cd2+, Cu2+, Ni2+, and Pb2+ ions from aqueous solutions using tururi fibers as an adsorbent under both batchwise and fixed‐bed conditions. It was found that modification of the tururi fibers with sodium hydroxide increased the adsorption efficiencies of all metal ions studied. The fractional factorial design showed that pH, adsorbent mass, agitation rate, and initial metal concentration influenced each metal adsorption differently. The kinetics showed that multi‐element adsorption equilibria were reached after 15 min following pseudo‐second‐order kinetics. The Langmuir, Freundlich, and Redlich–Peterson models were used to evaluate the adsorption capacities by tururi fibers. The Langmuir model was found to be suitable for all metal ions. Breakthrough curves revealed that saturation of the bed was reached in 160.0 mL with Cd2+ and Cu2+, and 52.0 mL with Ni2+ and Pb2+. The Thomas model was applied to the experimental data of breakthrough curves and represented the data well. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40883.

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 2(4-1) 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 Cu(2+) and Pb(2+), 20 min for Ni(2+) and instantaneously for Cd(2+). 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.

In this study is reported an interdisciplinary approach to teaching chemistry using case studies seeking to stimulate the students in the learning process as well as to develop their critical thinking. The focuses were in chemical multiple equilibrium from an environmental problem based on the quantitative assessment of the dissolution process of limestone sediment containing in a water body by the action of acid rain and increasing of the CO 2 atmospheric concentration. The variables considered were pluviometric average, CO 2 , SO 2 and NO 2 levels in the atmosphere as well as their dissolution equilibria and CaCO 3 sediment precipitation. This study is an important teaching tool that can be applied in undergraduate and postgraduate chemistry courses with emphasis in Analytical and Environmental Chemistry, engaging students in active discussion about issues and problems inherent to practical applications.