Multi-Element Analysis Based on an Automated On-Line Microcolumn Separation/Preconcentration System Using a Novel Sol-Gel Thiocyanatopropyl-Functionalized Silica Sorbent Prior to ICP-AES for Environmental Water Samples

A Low-Cost Colorimetric Assay for the Analytical Determination of Copper Ions with Consumer Electronic Imaging Devices in Natural Water Samples

This study reports a new approach for the determination of copper ions in water samples that exploits the complexation reaction with diethyldithiocarbamate (DDTC) and uses widely available imaging devices (i.e., flatbed scanners or smartphones) as detectors. Specifically, the proposed approach is based on the ability of DDTC to bind to copper ions and form a stable Cu-DDTC complex with a distinctive yellow color detected with the camera of a smartphone in a 96-well plate. The color intensity of the formed complex is linearly proportional to the concentration of copper ions, resulting in its accurate colorimetric determination. The proposed analytical procedure for the determination of Cu²⁺ was easy to perform, rapid, and applicable with inexpensive and commercially available materials and reagents. Many parameters related to such an analytical determination were optimized, and a study of interfering ions present in the water samples was also carried out. Additionally, even low copper levels could be noticed by the naked eye. The assay performed was successfully applied to the determination of Cu²⁺ in river, tap, and bottled water samples with detection limits as low as 1.4 µM, good recoveries (89.0-109.6%), adequate reproducibility (0.6-6.1%), and high selectivity over other ions present in the water samples.

Tailoring Nanoadsorbent Surfaces: Separation of Rare Earths and Late Transition Metals in Recycling of Magnet Materials

Novel silica-based adsorbents were synthesized by grafting the surface of SiO₂ nanoparticles with amine and sulfur containing functional groups. Produced nanomaterials were characterized by SEM-EDS, AFM, FTIR, TGA and tested for adsorption and separation of Rare Earth Elements (REE) (Nd³⁺ and Sm³⁺) and Late Transition Metals (LTM) (Ni²⁺ and Co²⁺) in single and mixed solutions. The adsorption equilibrium data analyzed and fitted well to Langmuir isotherm model revealing monolayer adsorption process on homogeneously functionalized silica nanoparticles (NPs). All organo-silicas showed high adsorption capacities ranging between 0.5 and 1.8 mmol/g, depending on the function and the target metal ion. Most of these ligands demonstrated higher affinity towards LTM, related to the nature of the functional groups and their arrangement on the surface of nanoadsorbent.

Dual-Modal Photoelectrochemical and Visualized Detection of Copper Ions

Copper is one of the extensively utilized heavy metals in modern industry and can be easily released into the environment due to high solubility of copper ions (Cu²⁺). Its percolation in water and accumulation along the food chain pose a serious threat to human health. Hence, it is of great significance to explore a novel, facile, and sensitive detection method for Cu²⁺. Based on the intriguing photo-to-electricity conversion process of CdS QDs, as well as desirable electrochromic property of WO₃ NFs, a dual-modal photoelectrochemical (PEC) and visualized detection platform for Cu²⁺ is fabricated. The electrochromic WO₃ NFs act as a display for the Cu²⁺ concentration, of which the color change could be observed directly by the naked eye, while the PEC signal provides accurate data for further analysis. In this work, a sensitive detection of Cu²⁺ in the range of 1 × 10^-5 to 5 × 10^-4 M is achieved, with a detection limit of 3.2 × 10^-6 M. The dual-modal analysis gives more choices for signal readouts with enhanced quantification reliability, which is adaptive for diverse application scenarios, especially for on-site investigation. This protocol offers a prototype for quick and reliable detection of the Cu²⁺ concentrations, and is promising for other environmental pollutants.