A promising modified polyvinyl chloride for adsorption of boron: Preparation, adsorption kinetics, isotherm, and thermodynamic studies

A new promising N-methyl-D-glucamine modified polyvinyl chloride via methyl glycinate linker (PVC-MG-NMDG) was designed to extract boron from tourmaline ore from the Sikait area in the South Eastern Desert of Egypt, which assays 10.43% B₂O₃. Specifications for PVC-MG-NMDG composite were executed successfully utilizing sundry approaches, such as FT-IR, XPS, GC–MS, TGA, BET, EDX, ¹³C-NMR, ¹H-NMR, ICP-OES, and XRD, which assure an acceptable synthesis of PVC-MG-NMDG. Optimized factors like pH, agitation time, primary boron concentration, composite dose, co-ions, eluting agents, and temperature have been improved. At ambient temperature, pH 9, 10 min of agitation, and 0.0138 mol/L boron ions (150 ppm), the PVC-MG-NMDG composite has a 25 mg/g maximal uptake. The extraction-distribution isotherm modeling suggests that the Langmuir model, with a theoretical value of 25.38 mg/g, more closely matches the practical value of 25 mg/g than the Freundlich model. The adsorption kinetics of boron ions by PVC-MG-NMDG were predicted with high accuracy using a pseudo-second order kinetic model, yielding a theoretical retention capacity of 27.93 mg/g. The extraction process was predicted, as shown by thermodynamic calculations, exothermic, spontaneous, and optimal extraction at low temperature; the thermodynamic factors controlling ΔS (−0.04 kJ/mol), ΔH (−13.74 kJ/mol), and ∆G values rise from −1.82 kJ/mol at 298 K to −0.19 kJ/mol at 338 K. Boron ions can be eluted from the overloaded composite by 0.5 M H₂SO₄ with a 95% efficiency rate. It was established that PVC-MG-NMDG composite reveals a worthy separation factor to most co-ions and gives a good separation power. Boric acid with a boron content of 17.23% and purity of 98.56% can be obtained through alkali fusion with NaOH flux and subsequent adsorption using a PVC-MG-NMDG composite.

Highlights

• A New modified polyvinyl chloride (PVC-MG-NMDG) was successfully prepared.
• The characteristics of new composite were verified via different techniques.
• The new composite reached its maximum boron absorption of 25 mg/g at 25°C.
• The extraction as an exothermic, spontaneous process at low temperature.
• The new composite has been applied to a real sample of Sikait tourmaline ore.