Basic Dye Adsorption onto Clay/ MnFe 2 O 4 Composite: A Mechanistic Study Adeela Kanwal 1 , Haq Nawaz Bhatti 1 , Munawar Iqbal 2* and Saima Noreen 1 ABSTRACT: Native, HCl pretreated clay and MnFe 2 O 4 /clay composite were investigated as an adsorbent for crystal violet (CV) removal. The adsorption behavior of dye was studied in batch experiments as a function of contact time, adsorbent dose, pH, dye initial concentration and temperature. The medium pH 8, contact time 30 min, MnFe 2 O 4 /clay composite dose 0.05 mg/ L, temperature 35 8C and 100 mg/L dye initial concentration furnished maximum CV adsorption. Adsorption data fitted well to the Langmuir isotherm model and maximum CV dye adsorption capacity of composite was 49.74 mg/g. The thermodynamic parameters revealed that the adsorption process of CV was exothermic and spontaneous in nature. CV adsorption followed the pseudo second order kinetic model. MnFe 2 O 4 /clay composite exhibited good CV adsorption ca- pacity and can be used as an alternative adsorbent for the removal of basic dyes from effluents. Water Environ. Res., 89, 301 (2017). KEYWORDS: basic dye, clay, composite, isotherm, kinetic, thermodynamics. doi:10.2175/106143017X14839994522984 Introduction Rapid industrial growth leads to contamination of water bodies with toxic chemicals. Among contamination sources, textiles are playing a significant role (Jafarinejad, 2016b; Jamal et al., 2015; Qureshi et al., 2015; Singh et al., 2015; Ukpaka et al., 2015; Ukpaka and Collins, 2016; Van Hoa et al., 2016). An average sized textile mill having a production of about 8000 kg of fabric per day consumed about 1.6 million liters of water (Petcu et al., 2016). Discharge of the colored effluent into water bodies results in the depletion of dissolved oxygen, causing anoxic conditions that are lethal to aquatic organisms (Hayat et al., 2015). As a result of uncontrolled discharge, dyes are frequently found in surface and subsurface water sources as well as in landfill leachates due to the stable nature of the dyes (Iqbal et al., 2013; Jamal et al., 2015; Manzoor et al., 2013; Qureshi et al., 2015; Ullah et al., 2013). Therefore, for the removal of dyes to prevent contamination of water bodies, efficient remediation strategies must be adopted (Amadi and Ukpaka, 2015; Jafarinejad, 2016a; Majolagbe et al., 2016; Peter and Chinedu, 2016; Sayed, 2015; Shindy, 2016; Ukpaka, 2016a; Ukpaka, 2016b, c; Ukpaka, 2016d; Ukpaka, 2016e). The adsorption using different types of adsorbents is an efficient, cheap and simple method for dye remediation. More recently, the application of composites has gained the attention of the scientific community in view of various advantages (Duta and Visa, 2015; Liu et al., 2016). A composite is a combination of two or more components such as a reinforcing agent and a compatible matrix that offer excellent adsorption properties (Rangabhashiyam and Selvaraju, 2015) and to date clinoptilolites ( ¸Coruh et al., 2010), mon- timorillonites (Akar et al., 2009), esmectites (Galindo et al., 2013), kaolinites (Wang et al., 2014) and bentonites (Anna et al., 2015) have been successfully employed as adsorption. Authors have correlated the enhanced adsorption of composites with physicochemical stability, high superficial area and cation exchange capacity of composites (Cantuaria et al., 2015). Bentonite contains a high proportion of swelling clays and is mainly composed of montmorillonite with a composition of SiO 2 , Al 2 O 3 , CaO, MgO, Fe 2 O 3 , Na 2 O, and K 2 O (Guo et al., 2012). Clays offer an attractive and inexpensive option for the removal of organic and inorganic contaminants, which is also low-cost, environmentally friendly, cheap and abundantly present in nature (Adesola et al., 2016; Babarinde and Onyiaocha, 2016; Iqbal and Khera, 2015). The bentonite in different forms i.e., organotailored, acid and base treated, china clay and wallastonite have been extensively studied as sorbent (Hassani et al., 2015; Oliveira et al., 2003). Moreover, supramolecular gel composites reinforced by using halloysite nanotubes loading with in-situ formed Fe 3 O 4 nanoparticles (Zeng et al., 2016), chemically modified nanoclay (Hassani et al., 2015), polyoxometalate-based metal–organic framework (Liu et al., 2016), Co 3 O 4 –ZrO 2 composites (Singh et al., 2015), fly-ash– TiO 2 (Duta and Visa, 2015), activated carbon/c-Fe 2 O 3 (Fayazi et 1 Department of Chemistry, University of Agriculture, Faisalabad 38000, Pakistan 2 Department of Chemistry, The University of Lahore, Raiwind Road, Lahore, Pakistan * Department of Chemistry, The University of Lahore, Raiwind Road, Lahore, Pakistan; email: bosalvee@yahoo.com WATER ENVIRONMENT RESEARCH  April 2017 301