Cu2+, Cr3+, and Ni2+ in mono- and multi-component aqueous solution adsorbed in passion fruit peels in natura and physicochemically modified: a comparative approach

Among the low-cost adsorbent are agricultural residues, which can be used in natura or modified forms. This work evaluated the adsorption of Ni²⁺, Cu²⁺, and Cr³⁺ in mono- and multi-component aqueous solutions using passion fruit peels in natura (Nat-PF) and physicochemically modified (Mod-PF). The adsorption was investigated by kinetic and isotherm models. A comparative investigation was conducted to analyze the effect of the experimental conditions by statistical test, adsorption capacity ratio, selectivity of adsorbate, and distribution coefficient. In both adsorbents, the process occurs in monolayer by chemosorption. Equilibrium was reached after 30 min, with highest adsorption capacity for Cu²⁺ as 0.495 mg g^-1, for Cr³⁺ as 0.483 mg g^-1, and for Ni²⁺ as 0.464 mg g^-1. The adsorption in Mod-PF was less affected in multi-component solutions, reducing the adsorption capacity by 0.06-0.15 times when compared to monocomponent solutions, while in Nat-PF a reduction of more than half of adsorption capacity was obtained. The modifications imposed on the biomass led to a change in its adsorptive selective, being Cr³⁺  > Cu²⁺  > Ni²⁺ for Nat-PF and Cu²⁺  > Ni²⁺  > Cr³⁺ for Mod-PF.

Comparison of design, materials selection and characterization of pacifiers produced in Brazil

BACKGROUND

A pacifier is an object designed for use by children aged two weeks to around five years old. Although a convenient and an efficient alternative to children sucking their thumb, its use is highly questionable. With the advancement of medicine and technology, harms related to its use were discovered and were related to poor development of the teeth. Furthermore, the use of some industrial raw materials may cause damage to the child's health during the growing process.

METHOD

This study evaluates different models of pacifiers available on the market, taking into consideration the design, materials and attendance to Brazilian Standards.

RESULTS

The Fourier Transform Infrared Spectroscopy (FTIR) analysis of the five different models of pacifiers indicates the use of different materials. For models A, B and E, the nipple is basically composed of silicone, while the guard is made of polycarbonate. For model C and D, the nipple is basically composed of natural rubber, while the guard and the ring are made of polycarbonate. For model D and E, however, the presence of Bisphenol A (BPA) was also used in composition. For the tensile strength tests, only model C was disapproved.

CONCLUSION

Silicon and natural rubber satisfy the requirements for technical performance. However, this does not take into account hygiene and toxicity as parameters for the selection, which are also important when considering child health.