Extração e pré-concentração de cádmio utilizando argila expandida como uma nova fase sólida em sistema DPX com detecção espectrofotométrica e eletroquímica

Abstract

The development of new analytical methods is crucial for solving environmental contamination issues and ensuring the safety of human life and the environment. In recent years, solid-phase extraction (SPE) has been successfully used for the extraction and determination of low levels of metal ion concentrations. While solid-phase extraction is well-established, its application for trace metal determination has been less explored compared to classical SPE, which is mostly focused on organic compounds. The objective of Chapter 1 of this thesis was to utilize the Disposable Pipette Extraction (DPX) procedure to develop a new solid phase using expanded clay. This solid phase was used for the extraction and pre-concentration of Cd(II) ions in drinking water. Characterization of the expanded clay through scanning electron microscopy revealed favorable morphological characteristics for adsorption. Energy-dispersive spectroscopy confirmed the composition of the clay with elements important for adsorption. Zero point of charge studies indicated that the clay surface has negative charges, enhancing the interaction with cationic ions. The adsorption capacity was evaluated using Langmuir isotherms, resulting in a maximum adsorption capacity of 1384.38 mg g-1. Studies were conducted to determine the optimal conditions for analyte extraction and elution, and the method validation demonstrated satisfactory results in terms of determination coefficient, pre-concentration factor, detection limit, and recovery. The method was successfully applied to river water samples. In Chapter 2, a miniaturized electrochemical device with integrated electrodes printed using a 3D pen was developed, coupled with DPX, for the determination of Cd(II) by square wave anodic stripping voltammetry. This system achieved lower detection limits than the FAAS detection method and exhibited similar DPX characteristics (pre-concentration factor), with the advantage of being lower cost, more portable, and requiring a smaller eluent volume.