_applied sciences_  
_Article_  
Iron Removal from Low-Grade Pyrophyllite Ore by Microwave Irradiation and Dry Magnetic Separation  
[PERSON] 1,*\({}^{\text{\text{\textcircled}}}\), [PERSON] 2\({}^{\text{\textcircled}}\) and [PERSON] 3,4,*\({}^{\text{\textcircled}}\)  
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Pyrophyllite is mostly produced in Korea, Japan, India, Thailand, Saudi Arabia, Peru, and South Africa [16]. However, the primary producers of high-purity pyrophyllite, which is widely used in filler and fiberglass applications, are China, Japan, and Korea [16].  
The quality and price of pyrophyllite depend mainly on its content of Al\({}_{2}\)O\({}_{3}\) and impurities [17]. High-purity ore is desirable because of its high alumina content and acceptable levels of iron and titanium, whereas low-purity ore has higher levels of iron and titanium and a lower alumina content, making it less desirable for industrial applications [18,19]. Impurities such as titanium (Ti) and iron (Fe) adversely influence the final product [6,20], affecting its color and other characteristics. The presence of Fe lowers the melting point of refractory materials, reduces the mechanical strength of ceramics, and reduces transmission in optical fibers [21]. Therefore, the acceptable percentages of Fe and Ti in pyrophyllite ore are determined by industry. Industries such as refractory and paper have specific limits for Fe and Ti content < 1%, while pottery, tiles, and fillers this is <0.5% [6,22,23,24]. Since high-grade pyrophyllite ore are rarely found naturally, and the industry's increasing demand has led to their rapid depletion, there has been a need to explore low-quality pyrophyllite ores. Low-quality pyrophyllite ores exist in large quantities with high Fe contents, which hinder their industrial use. Low-grade pyrophyllite ore treatment aims to raise the alumina content and remove impurities, particularly Fe- and Ti-bearing minerals, through economic and effective treatment techniques [4,6,25]. Upgrading processes for low-grade pyrophyllite ore, such as physical and chemical separation and combination techniques, are based on the gangue minerals and ore characteristics [26,27]. Magnetic separation methods are particularly effective for paramagnetic and ferromagnetic impurities. Dry high-intensity magnetic separation is used to remove iron-containing minerals from pyrophyllite for industrial use [6,28,29]. Parameters such as magnetic intensity, particle size, magnetic roll speed, feed rate, and solid content are crucial considerations in this process [4]. The combination of microwave roasting radiation and dry high-intensity magnetic separation is considered a promising and environmentally friendly technique for enhancing the iron removal efficiency from low-grade pyrophyllite [20,30]. Compared with conventional techniques, microwave heating has the advantage of allowing for volumetric heating because of its deep penetration into the sample. Moreover, certain iron minerals react with microwaves in a selective manner to form ferromagnetic phases, which improve their magnetic properties [27,31]. The microwave irradiation time and magnetic field intensity are the most important operating variables for this method [21].  
Therefore, this study examined the removal of iron from Saudi low-grade pyrophyllite ore using two approaches. The first approach involves dry high-intensity magnetic separation, while the second involves microwave pretreatment of the ore samples before dry magnetic separation. For the dry high-intensity magnetic separation approach, the iron removal efficiency was investigated by changing different operating parameters such as roll speed, feed rate, field intensity, and feed particle size. Alternatively, for the combined method (microwave treatment followed by dry magnetic separation), the microwave irradiation time and magnetic field intensity were studied.