Determination of copper in seawater based on a liquid membrane preconcentration system

Rapid, sensitive, and selective copper (II) determination using sensitive chromogenic azo dye based on sulfonamide

A simple methods have been developed for determination of Cu(II) ions in aqueous solutions. The spectrophotometric method relied mainly on the reaction between Cu(II) ions and the azo dye ligand named N-diaminomethylene-4-(2,4-dihydroxy-phenylazo)-benzenesulfonamide (H₂L) at pH 10.0. The influence of parameters such as concentration, pH and reaction time were inspected. A linear relationship (R² = 0.9992) between absorbance and the concentration of Cu(II) was obtained at themaximum absorptionpeak of 474 nm within 1.6-9.6 × 10^-6 mol L^-1 concentration range. The limit of detection for Cu(II) ion and limit of quantitation were 1.1 × 10^-7 mol L^-1 and 3.7 × 10^-7 mol L^-1, respectively.The potentiometric method is based on a novel poly(vinyl chloride) membrane, containing the synthesized azo dye as an ionophore, was used to developed a Cu(II)- selective sensor. This newly developed sensor revealed a Nernstian response over Cu²⁺ ion in a concentration range 1.0 × 10^-6-1.0 × 10^-2 mol L^-1 with cationic slopes of 29.5 ± 0.2 mV decade^-1 and detection limits of 3.0 × 10^-6 mol L^-1 copper(II) for o-nitrophenyl-octyl ether (o-NPOE) based membrane sensor. The electrode showed good discrimination toward Cu²⁺ ions with respect to most common cations. The advantages of the proposed methods are their simplicity, selectivity, and high sensitivity. In addition, the sensor has been used as indicator electrode in the potentiometric titration of Cu²⁺ ion against EDTA. The structure and geometry of the complex formed between Cu(II) and H₂L ligand was identified via isolation of the solid complex; Co(II) an Ni(II) complexes were synthesized as well. The geometrical structure around the metal centers were proved to be square planar for Cu(II) complex and tetrahedral for Co(II) an Ni(II) complexes.

Transportation and kinetic analysis of Mo(VI) ions through a MDLM system containing TNOA as carrier

In this report, Mo(VI) ions are transported from an aqueous donor phase into an aqueous acceptor phase by a newly designed method called as multi dropped liquid membrane (MDLM) system prepared by dissolving TNOA as carrier in kerosene. During the extraction of Mo(VI) ions by the liquid membrane system; 100ppm Mo(VI) solutions as donor phase, buffer solution(pH:9.5) and Na2CO3 in different concentrations as acceptor phase and TNOA diluted by kerosen as organic phase are used.In our experimental work, the effect of temperature by using buffer solution and Na2CO3 in the acceptor phase and effect of concentration of acceptor phase on the extraction of Mo(VI) ions were investigated. Appropriate conditions for Mo(VI) transportation were as follows: pH of donor phase is 2.00, concentration of TNOA is 0.005M, 1.00M Na2CO3 as acceptor phase, and flux rate is 50mL/min. Besides, Mo(VI) ion transportation is consecutive first order irreversible reaction and the transportation of Mo(VI) ions is diffusion controlled process. The kinetic parameters (k1, k2, Rm(max), tmax, Jd(max), Ja(max)) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions.

Equilibrium Sampling through Membranes of Freely Dissolved Copper Concentrations with Selective Hollow Fiber Membranes and the Spectrophotometric Detection of a Metal Stripping Agent

A sensitive spectrophotometric method for the determination of freely dissolved copper concentrations in aqueous samples after preconcentration with hollow fiber membrane extraction has been developed. The method is based on the equilibrium sampling through a selective membrane into an acceptor solution containing 4-(pyridyl-2-azo)resorcinol (PAR), which serves as stripping agent and metal indicator. Negligible extraction of interferences and equilibrium enrichment of copper allowed for selective spectrophotometric determination of the Cu-PAR complex. Some important extraction parameters such as acceptor composition, shaking, equilibrium time, and sample volume were studied. The optimized methodology showed good linearity in the range of 5-100 microg/L, an enrichment factor of 93, good repeatability and reproducibility (RSDs < 6%, n = 6), and a detection limit of 4 microg/L. The cationic metals Ni2+, C(2+, Cd2+, Fe3+, Pb2+, Zn2+, and Mn2+ were shown not to interfere with the measurement of Cu2+. Measurements on samples containing mixtures of various ligands and cations were in good agreement with theoretically calculated concentrations, and the method was also applied to environmental samples. The developed technique requires less labor and less sophisticated equipment than conventional methods typically based on atomic absorption spectrometry or ICP.

Determination of free copper concentrations in natural waters by using supported liquid membrane extraction under equilibrium conditions

A method is described for measurement of freely dissolved copper concentrations in natural water samples using supported liquid membrane (SLM) extraction under equilibrium conditions, a technique denoted "equilibrium sampling through membranes" (ESTM). For this purpose, 1,10-dibenzyl-1,10-diaza-18-crown-6 as neutral carrier and oleic acid were used in the membrane phase. The main variables optimised were the carrier used to form the metal complexes, the organic solvent used in the membrane, the countercation, pH, the ligand used in the acceptor phase, the extraction time, and the flow rate of the donor phase. After the optimisation process an enrichment factor of 18.5 was obtained. Equilibrium conditions were reached after extraction for 60 min if a flow rate of 1.0 mL min(-1) or greater was used. When different ligands such as humic acids, phthalic acid, and EDTA were added to the sample solution, and sample pH ranged from 6 to 8, the results obtained for freely dissolved copper concentrations were in a good agreement with results from speciation calculations performed with Visual Minteq V 2.30, Cheaqs V L20.1, and WinHumic V. The developed technique was applied to analysis of stream and leachate water.