The surface area for [email protected] was calculated by N2 adsorption/desorption isotherms using Brunauer/Emmett/Teller

The surface area for [email protected] was calculated by N2 adsorption/desorption isotherms using Brunauer/Emmett/Teller (BET). Figure 4A shows that the isotherm for sorption and desorption of N2 onto [email protected] is nearly similar to ? type of IUPAC classification (Lowell et el., 2011), proving mesopores dominated property. Amount adsorbed increases gradually as a relative pressure increases. The lower line was the nitrogen adsorption isotherm and the upper line was the nitrogen desorption isotherm. The hysteresis loop is explained as type H3 representing aggregates of plate-like particles giving a slit-shaped pore. The surface area of [email protected] (10.6 m2/g) is higher than the surface area of polyurethane foam (2.8 m2/g) (Han et el., 2015). Barrett/Joyner/ Halenda (BJH) methods were used to find pore volume and pore radiuses are 0.017 cm3/g and 4.124 nm (Fig. 4B). The ratio of mesopores to micropores volumes (1.7× 10-2 cm3/g: 1.5×10-3 cm3/g) is 11:1; such a ratio indicates that the [email protected] would be a good candidate for the removal of dyes.
Figure 4
Iodine number (IN) is the way to know the micro-pore content of surface. The iodine molecule is relatively small with an area of 0.4 nm2 and can enter in the smaller micro pores (Alaya et el., 2000; Baçaoui et el., 2001). The iodine number can use for approach determination of surface area and microporosity (? 2 nm) of the sorbent (Nunes and Guerreiro, 2011; Saka, 2012). The iodine number of [email protected] is 3.62 mmol/g (459.05 mg/g). The specific surface area of [email protected] was also estimated using iodine number () (Wu, 2007; Mianowski, 2007) where S is the area occupied by adsorbed iodine molecules at the maximum mono-layer surface coverage (m2/g), N is the Avogadro number (6.02 ×1023), A is the iodine surface area (0.2096 ×10?18 m2) and M is the iodine molar mass (126.92 g/mol). So, the specific surface area obtained is 456.4 m2/g. The BET surface area of [email protected] is very small compared with calculated surface area by iodine number method. It indicates that the iodine number method is incorrect for determination of [email protected] surface area (Tran, 2017). Thus it can be concluded that the adsorption process of iodine molecules occurred not only by the pores of the surface of [email protected] but also through its functional groups e.g. ether groups.
The methylene blue number is defined as the maximum amount of dye adsorbed by 1 g of adsorbent (Nunes and Guerreiro, 2011). Methylene blue can measure mesporsity (2-50 nm) of the sorbent and evaluate its cation exchange (Tounsadi et el., 2016). The surface area of MB is 2.08 nm2 and can enter in micropores and mesopores (Nunes and Guerreiro, 2011). The methylene blue number for [email protected] is 0.84 mmol/g (270.25 mg/g). This value indicates that the surface of [email protected] contains mesopores and also has better cation-exchange capacity compared to other sorbents (Table 1)
Different concentration of Br.G, To.B and Tr.B dyes (2-12 mg/L) was plotted against capacity of [email protected] The R2 values for the sorption of Br.G, To.B and Tr.B dyes [email protected] onto were 0.962, 0.990 and 0.994. Also, the intercept values of these plots were 0.013, 0.019 and 0.011, respectively as shown in table 2. In addition the estimated capacity (Q) of [email protected] for Br.G, To.B and Tr.B were 0.47, 0.30 and 0.19 mmol/g (227, 91.7 and 182.5 mg/g), respectively. The results indicate that the [email protected] has a good sorption capacity compared to other sorbents (Table 1, 2).


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