Table 4.

Metallic mordants utilized for natural dyeing.

Name	Fibers	Key Features	Ref.
Alum Compound - KAI(SO4)2; Al2(SO4)3; AlCl3; Al (NO3)3	Wool	Brightening mordants; Strong affinity for both cellulose and protein fibers; Form an insoluble complexes; Enhanced color depth; Keep original shade; Improve light and wash colorfastness; Less toxicity than others.	(Zarkogianni et al., 2011; Yi and Yoo, 2010; Mansour, 2010; Farizadeh et al., 2010; Erdem Işmal et al., 2013; Deveoglu et al., 2012a, Deveoglu et al., 2012b; Ghaheh et al., 2012; Khan et al., 2012; Shahid et al., 2012; Guesmi et al., 2012a; Yusuf et al., 2012; Deveoglu et al., 2012a, Deveoglu et al., 2012b; Tutak and Benli, 2012; Ghouila et al., 2012; Ebrahimi and Parvinzadeh Gashti, 2016; Sadeghi-Kiakhani, 2015; Nazari et al., 2014; Zhang et al., 2014; Shabbir et al., 2016; Islam and Mohammad, 2018; Shabbir et al., 2018; Shahid-ul-Islam et al., 2018a, Shahid-ul-Islam et al., 2018b; Lee et al., 2018; Yan et al., 2019; Fröse et al., 2019; Rather et al., 2020; Adeel et al., 2020; Peran et al., 2020; Haji, 2020; Zhang et al., 2020; dos Silva et al., 2020; Jabar et al., 2020)
	Cotton; Flax; Jute; Ramie; Bamboo; Lyocell; Viscose		(Vankar and Shukla, 2011; Zarkogianni et al., 2011; Arroyo-Figueroa et al., 2011; Yi and Yoo, 2010; Farizadeh et al., 2010; Bhatti et al., 2010; Rehman et al., 2013; Batool et al., 2013; Velmurugan et al., 2013; Savvidis et al., 2013; Tutak and Benli, 2012; Chattopadhyay et al., 2015; Davulcu et al., 2014; Zhao et al., 2014; Grifoni et al., 2014; Swami et al., 2014; Chattopadhyay et al., 2014; Dehnavi et al., 2016; Benli and Bahtiyari, 2018a; Ding and Freeman, 2017; Nakpathom et al., 2017; Adeel et al., 2017; Rehman et al., 2018; Lee et al., 2018; Sadeghi-Kiakhani et al., 2018a, Sadeghi-Kiakhani et al., 2018b; Azeem et al., 2019; Mir et al., 2019; Faisal and Chafidz, 2019; Kumbhar et al., 2019; Fröse et al., 2019; Jaffer et al., 2019; Giacomini et al., 2020; Inprasit et al., 2020; Manicketh and Francis, 2020; Phan et al., 2020; dos Silva et al., 2020; Lohtander et al., 2020; Sinha et al., 2016; Benli and Bahtiyari, 2018a)
	Silk		(Vankar and Shukla, 2011; Vinod et al., 2011; Yi and Yoo, 2010; Farizadeh et al., 2010; Vinod et al., 2010; Punrattanasin et al., 2013; Deveoglu et al., 2012a, Deveoglu et al., 2012b; Wang et al., 2013; Baliarsingh et al., 2012; Mahmud-Ali et al., 2012; Deveoglu et al., 2012a, Deveoglu et al., 2012b; Torgan et al., 2015; Ajmal et al., 2014; Tayade and Adivarekar, 2016; Dehnavi et al., 2016; Jia et al., 2017; Vankar et al., 2017; Giacomini et al., 2017; Yin et al., 2017; Khan et al., 2018; Lee et al., 2018; Yan et al., 2019; Adeel et al., 2019; Rungruangkitkrai et al., 2020)
	Nylon; Polyester; Acrylic		(Hunger et al., 2005; Guesmi et al., 2012b; Sadeghi-Kiakhani, 2015; Shams Nateri et al., 2016; Ebrahimi and Parvinzadeh Gashti, 2016; Erdem Ismal and Yıldırım, 2020; Erdem Ismal and Yıldırım, 2020; Nakpathom et al., 2019)
Ferrous Compound - FeSO4; FeCl3	Wool	Dulling mordants; Highest achievable K/S values; Form coordination complex – chelating; increase fastness of any colors; Grey to black shades; Prefer to cellulosic fibers.	(Zarkogianni et al., 2011; Yi and Yoo, 2010; Farizadeh et al., 2010; Erdem Işmal et al., 2013; Rehman et al., 2013; Ghaheh et al., 2012; Khan et al., 2012; Yusuf, M. et al., 2012; Mahmud-Ali et al., 2012; Tutak and Benli, 2012; Ghouila H. et al., 2012; Ebrahimi and Parvinzadeh Gashti, 2016; Li et al., 2016; Shabbir et al., 2016; Shabbir et al., 2018; Shahid-ul-Islam et al., 2018a, Shahid-ul-Islam et al., 2018b; Rather et al., 2019; Yan et al., 2019; Fitz-Binder and Bechtold, 2019; Rather et al., 2020; Adeel et al., 2020; Glogar et al., 2020; dos Silva et al., 2020)
	Silk		(Yi and Yoo, 2010; Punrattanasin et al., 2013; Wang et al., 2013; Baliarsingh et al., 2012; Mahmud-Ali et al., 2012; Tayade and Adivarekar, 2016; Patil and Datar, 2016; Patil and Datar, 2016; Jung, 2016; Yasukawa et al., 2017; Jia et al., 2017; Khan et al., 2018; Rather et al., 2019; Adeel et al., 2019; Rungruangkitkrai et al., 2020)
	Cotton; Flax; Jute; Lyocell		(Batool et al., 2013; Yi and Yoo, 2010; Tutak and Benli, 2012; Chattopadhyay et al., 2015; Davulcu et al., 2014; Zhao et al., 2014; Swami et al., 2014; Khan et al., 2014; Chattopadhyay et al., 2014; Li et al., 2016; Benli and Bahtiyari, 2018a; Yasukawa et al., 2017; Ding and Freeman, 2017; Nakpathom et al., 2017; Adeel et al., 2017; Rehman et al., 2018; Azeem et al., 2019; Sheikh et al., 2019; Mir et al., 2019; Faisal and Chafidz, 2019; Kumbhar et al., 2019; Giacomini et al., 2020; dos Silva et al., 2020; Benli and Bahtiyari, 2018a)
	Nylon; Polyester; Acrylic		(Guesmi et al., 2012b; Erdem Ismal and Yıldırım, 2020; Nakpathom et al., 2019; Erdem Ismal and Yıldırım, 2020)
Copper Compound - CuSO4; CuCl2	Cotton; Flax; Lyocell	Dulling mordants; Normally much stronger than those of iron; Higher dye uptake than others; Eco and toxicity concern.	(Yi and Yoo, 2010; Kobayashi et al., 2010; Batool et al., 2013; Tutak and Benli, 2012; Davulcu et al., 2014; Swami et al., 2014; Khan et al., 2014; Benli and Bahtiyari, 2018a; Yasukawa et al., 2017; Nakpathom et al., 2017; Adeel et al., 2017; Rehman et al., 2018; Amemiya and Nakanishi, 2018; Azeem et al., 2019; Mir et al., 2019; Kumbhar et al., 2019; Manicketh and Francis, 2020; Benli and Bahtiyari, 2018a; Yadav et al., 2019)
	Wool		(Zarkogianni et al., 2011; Ghoranneviss et al., 2011; Yi and Yoo, 2010; Farizadeh et al., 2010; Erdem Işmal et al., 2013; Ghaheh et al., 2012; Tutak and Benli, 2012; Ghouila, H. et al., 2012; Ebrahimi and Parvinzadeh Gashti, 2016; Amemiya and Nakanishi, 2018; Yan et al., 2019; Rather et al., 2020; Adeel et al., 2020)
	Silk		(Yi and Yoo, 2010; Punrattanasin et al., 2013; Wang et al., 2013; Baliarsingh et al., 2012; Mahmud-Ali et al., 2012; Torgan et al., 2015; Ajmal et al., 2014; Tayade and Adivarekar, 2016; Yasukawa et al., 2017; Jia et al., 2017; Yan et al., 2019)
	Nylon		(Shams Nateri et al., 2016; Erdem Ismal and Yıldırım, 2020; Erdem Ismal and Yıldırım, 2020)
Stannous Compound - SnCl2; SnSO4; SnCl4;	Wool	Brightening mordants brighter than others; Improve colorfastness; May cause stiff hand; Loss tensile strength of fiber.	(Zarkogianni et al., 2011; Ghaheh et al., 2012; Khan et al., 2012; Shahid et al., 2012; Ghouila et al., 2012; Shabbir et al., 2016; Shabbir et al., 2018; Shahid-ul-Islam et al., 2018a, Shahid-ul-Islam et al., 2018b; Adeel et al., 2020; Barani and Maleki, 2020; Dehnavi et al., 2016)
	Silk		(Punrattanasin et al., 2013; Baliarsingh et al., 2012; Mahmud-Ali et al., 2012; Tayade and Adivarekar, 2016; Torgan et al., 2015);
	Cotton; Flax; Lyocell		(Davulcu et al., 2014; Torgan et al., 2015; Zhao et al., 2014; Swami et al., 2014; Wang et al., 2016; Rehman et al., 2018; Azeem et al., 2019; Kumbhar et al., 2019; Phan et al., 2020)
	Nylon		(Shabbir et al., 2016; Shams Nateri et al., 2016; Erdem Ismal and Yıldırım, 2020; Erdem Ismal and Yıldırım, 2020)
Potassium Compound - K2Cr2O7	Wool	Brightening mordants; Health and toxicity concern.	(Ghaheh et al., 2012)
	Cotton; Lyocell		(Swami et al., 2014; Benli and Bahtiyari, 2018a; Rehman et al., 2018)
	Silk		(Mahmud-Ali et al., 2012; Ajmal et al., 2014; Tayade and Adivarekar, 2016)
Other minor Compounds:∗	Cotton; Acrylic; Wool; Silk; Nylon.	Various, overall improve color depth and/or colorfastness	(Zarkogianni et al., 2011; Yi and Yoo, 2010; Farizadeh et al., 2010; Wang et al., 2013; Guesmi et al., 2012a, Guesmi et al., 2012b; Torgan et al., 2015; Parvinzadeh Gashti et al., 2014; Cerempei et al., 2016; Yasukawa et al., 2017; Khan et al., 2018; Erdem Ismal and Yıldırım, 2020; Yan et al., 2019; Faisal and Chafidz, 2019; Adeel et al., 2020; Peran et al., 2020; Zhang et al., 2020; Jabar et al., 2020)

^∗Zinc [ZnSO₄; ZnCl₂; Zn(BF₄)₂], Calcium [Ca(OH)₂; CaCl₂, Ca(CH₃COO)₂,CaO], Cobalt [CoSO₄], Magnesium [MgSO₄], Manganese [MnSO₄), Lanthanum Oxide [La₂O₃], Rare earth Chlorides [ReCl₃,NdCl₃, ZrOCl₂], Silver nitrate [AgNO₃], Ammonium sulfate [(NH₄)₂SO₄], Sodium acetate [C₂H₃NaO₂], Praseodymium chloride [PrCl₃], Kunipia-F Nano clay [NiSO₄].