Montmorillonite k10 nanoclay

Montmorillonite K10 nanoclay (CAS No: 1318-93-0; surface area according to the quality certification is 220–270 m²/g) was purchased from Sigma Aldrich Chemie GmbH (Steinheim, Germany). Carnauba wax (CAS No: 8015-86-9; it is in the form of yellow-brown flakes) was purchased from Naturprodukte Lembke GbR (Faulenrost, Germany).
Montmorillonite was mixed with carnauba wax at a temperature of 120–130 °C using a magnetic stirrer for 30 min before it was rapidly cooled with cold water to prevent the sedimentation of the nanoclay. The obtained solid samples of composite materials of wax/nanoclay with 50/50, 60/40, and 70/30 mass ratios were ground for 20 min to provide polydisperse powders, which were used for all experiments [69 (link)]. Further heat treatment (annealing) at 60 °C for 1 month of a sample of PCMs of wax/nanoclay and a 50/50 mass ratio was applied to study the effect of temperature on the storage condition of PCMs.

All chemicals, including sulfuric acid (H₂SO₄, 98%), sodium hydroxide (NaOH, ≥ 97.0%), and tetrazolium solution of Pb (II) ions (1000 mg/L) with 99% purity were purchased from Merck Co, (Germany). The montmorillonite-K10 nanoclay was purchased from Sigma Aldrich Company. Pb (II) ions concentrations measurement was performed using Atomic Absorption Spectrometer (YOUNGLIN, Model AAS 8020). The laboratory pH meter (Metrohm model 827 pH meter) was used for the pH determination.