Effect of the magnetic field produced by a Halbach array magnetizer on water UV absorption, removal of scale and change in calcium carbonate polymorphs

Abstract

In this paper, the influence of magnetic fields on the ultraviolet (UV) absorption of water circulated within three different magnetic configurations (inside, outside, and dual Halbach array magnetizers) is presented. Permanent magnets were inserted in the designed magnetizer and magnetic flux densities were varied between 380 and 580 mT. The samples presented evident UV absorption under magnetic fields due to the change of polarization in water molecules. The effectiveness of the magnetic field to remove the scale was investigated by measuring the calcium ion concentration after magnetic treatment. The dual Halbach array configuration enhanced scale removal by 41.4% at a water flow rate of 380 ± 3 mL min⁻¹. Different magnetic configurations were used to study the magnetic effect on calcite-aragonite CaCO₃ polymorphs. The magnetic memory of the magnetizer was assessed using the percentage formation of aragonite crystals. Overall, magnetizers improved the aragonite formation. Dual Halbach array magnetizers yielded the highest aragonite percentage. Even after 24 h (memory effect) of storage, the presence of the magnetic effect indicated the superiority of the proposed method for scale removal. Thus, magnetic technology is an environmentally friendly, cost-effective, and simple treatment for scale removal.