Evaluation Behavior for the Adsorptive of Ca(II) and Mg(II) Ions (Hardness of Water) from Water by Modified Copper Based on Metal Organic Frameworks and Potentiometric Sensors

Abstract

This study presents adsorption of Ca(II) and Mg(II) ions from water at different concentration. This causes problems such as corrosion and scaling. MOF–Cu (Cu₃(BTC)₂) and modified MOF–Cu were study as an adsorbent of Ca²⁺ and Mg²⁺ ions from water. The morphology and structure of the MOFs adsorbents were characterized by XRD, FT-IR, nitrogen adsorption/desorption and SEM methods. A batch test with various conditions was studied. The adsorption kinetics and isotherms are described. The experimental data were fitted to second-order-kinetics and Langmuir models. The adsorption capacity of MOF–Cu–GSH (4.6 mg/g (90.2%) and 6.2 mg/g (87.2%)) is higher than Cu₃(BTC)₂ (9.2 mg/g (81.2%) and 11.3 mg/g (77.4%)) for Ca(II) and Mg(II) ions respectively, through 6 h, 50 ppm, pH 7, 50 mg and 30°C. These potentiometric sensors respond to Mg(II) and Ca(II) ions in the wide linear concentration range of 1.0 × 10^–2–1.0 × 10^–7 and 1.0 × 10^–2–1.3 × 10^–7 mol L^–1 with Nernstian slopes of 30.04 ± 0.98 and 29.15 ± 0.44 mV decade^–1 of Mg(II) and Ca(II) ions and detection limit of 1 × 10^–7 and 1.3 × 10^–7 mol L^–1 for Mg–CPE (electrode IV) and Ca–CPE (electrode X), respectively. The electrodes were pH independent within the range of 2.5–7.5 and 3.0–8.0, with a fast response time of about 7 and 10 s for electrode (IV) and electrode (X), respectively. The results obtained were compared well with those obtained using inductively coupled plasma atomic emission spectrometry (ICP–AES).