SUMMARY

C HEMICALLY A CTIVATED B AEL S HELL

4.4 SUMMARY

In this chapter, batch adsorption studies of Pb²⁺, Ni²⁺, Sr²⁺, RB and MB dye using H2SO4 activated BS at 30^oC to 50^oC solution temperature was discussed. The results demonstrated that the adsorption capacity and BET surface area of the adsorbent increased significantly with increase in the concentration of H2SO4 for BS activation.

The pH of the metal and dye solution significantly influences the adsorption capacity of metals and dyes onto SBS. The pH 5.2, 5.8, 6.8, 3.5 and 7.0 for Pb²⁺, Ni²⁺, Sr²⁺, RB and MB dye was found to be the most favourable. The adsorption capacity of single metals onto SBS was decreased in binary and ternary system, but no significant alterations in the adsorption capacity in its metal-dye binary system. Presence of other cations at high concentration level decreases the adsorption capacity of three metals onto SBS, but no impact on dye adsorption capacities. The adsorption behaviour of heavy metal ions and cationic dyes onto SBS matched well with Langmuir isotherm model. The sorption kinetics of Pb²⁺, Ni²⁺, Sr²⁺ and MB dye was found to pseudo- second-order kinetics model. The adsorption process was exothermic for Pb²⁺ and

Sr²⁺ and endothermic for Ni²⁺, RB and MB dye. This work provides new insight for developing low-cost adsorbents from BS to remove the multimetal contaminants and cationic dyes from the aqueous solution including industrial wastewater.

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Figure 4.1 Effect of acid concentration on adsorption capacity; (Co = 100 (metals), 150 (dyes) mg/l, W = 0.06 g, V = 50 ml, T = 30^oC, t = 24 hr and R = 180 rpm)

Figure 4.2 SEM picture of (a) BS before H2SO4 treatment (b) BS after H2SO4 treatment

(a)

(b)

Figure 4.3 FT-IR spectra of (a) SBS before and after metal adsorption (b) SBS before and after dye adsorption

(a)

(b)

Figure 4.4 (a) Zeta potentials of SBS as a function of solution pH and (b) Electrophoretic mobility distribution of the SBS at pH 7.0

(b)

(a)

Figure 4.5 EDX spectra of SBS (a) before adsorption (b) after Pb²⁺

adsorption

(b)

(a)

Figure 4.5 EDX spectra of SBS (c) after Ni²⁺ adsorption (d) after Sr²⁺

adsorption

(d)

(c)

Figure 4.6 Effect of pH on adsorption of (a) Pb²⁺, Ni²⁺ and Sr²⁺ metal (b) RB

and MB dye [C_o = 100 (Pb²⁺, Ni²⁺ and Sr²⁺) and 200 (RB & MB dye) mg/l; pH = blank; W = 0.06 (Pb²⁺, Ni²⁺, Sr²⁺ and MB) and 0.05 (RB) g; V = 50 ml; t = equilibrium time (min); and T = 30^oC]

(a)

(b)

Figure 4.7 Effect of pH other ions on metal adsorption of (a) Pb²⁺ and (b) Ni²⁺

onto SBS: [Co = 100 mg/l (Pb²⁺ and Ni²⁺); pH = blank; W = 0.06 g;

V = 50 ml; t (equilibrium) = 90 (Pb²⁺) and 180 (Ni²⁺) min; and T = 30^oC]

(b)

(a)

Figure 4.7 Effect of pH other ions on metal adsorption of (c) Sr²⁺ and (d) RB onto SBS: [C_o = 100 (Sr²⁺) & 150 (RB); pH = blank; W = 0.06 (Sr²⁺) & 0.05 (RB) g; V = 50 ml; t = equilibrium (min); and T = 30^oC]

(d)

(c)

Figure 4.7e Effect of other ions on MB dye adsorption onto SBS: [Co = 150 mg/l; pH = blank; W = 0.06 MB g; V = 50 ml; t = equilibrium (min); and T = 30^oC]

Figure 4.8 Effect of (a) single metal adsorption at various metal concentrations onto SBS: (pH = blank, W = 0.1 g, V = 50 ml, t (equilibrium) = 90 (Pb²⁺), 180 (Ni²⁺) & 180 (Sr²⁺) min and T = 30ºC).

(a)

(e)

Figure 4.8 Effect of binary (b) (Pb²⁺+ Ni²⁺) and (c) (Pb²⁺+ Sr²⁺) metal adsorption at various metal concentrations onto SBS: (pH = blank, W = 0.1 g, V = 50 ml, t (equilibrium) = 90 (Pb²⁺), 180 (Ni²⁺) & 180 (Sr²⁺) min and T = 30ºC).

(b)

(c)

Figure 4.8 Effect of binary (d) (Ni²⁺ + Sr²⁺) and (e) ternary metal (Pb²⁺ + Ni²⁺ + Sr²⁺) adsorption system at various metal concentrations onto SBS:

(pH = blank, W = 0.1 g, V = 50 ml, t (equilibrium) = 90 (Pb²⁺), 180 (Ni²⁺) & 180 (Sr²⁺) min and T = 30ºC).

(d)

(e)

Figure 4.8 Effect of binary adsorption system of (f) equal mass of each (metal + dye) and (g) equal mass of each (dye + metal) onto SBS: (Co = 150 mg/l of each metal and each dye; pH = blank; W = 0.06 g; V = 50 ml; t (equilibrium) = 1440 min; and T = 30ºC).

(f)

(g)

Figure 4.9 Langmuir isotherm plots of (a) Pb²⁺ (b) Ni²⁺ and (c) Sr²⁺

adsorption onto SBS: (pH = blank; W = 0.06 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

(c)

Figure 4.9 Langmuir isotherm plots of (d) RB dye and (e) MB dye adsorption onto SBS: (pH = blank; W = 0.05 (RB) & 0.06 (MB) g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(d)

(e)

Figure 4.9 Langmuir isotherm plots of (f) Pb²⁺ (g) Ni²⁺ and (h) Sr²⁺

adsorption onto SBS in binary and ternary system: (pH = blank;

W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(f)

(g)

(h)

Figure 4.10 Freundlich isotherm plots of (a) Pb²⁺ (b) Ni²⁺ and (c) Sr²⁺

adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

(c)

Figure 4.10 Freundlich isotherm plots of (d) RB dye and (e) MB dye adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(e)

(d)

Figure 4.10 Freundlich isotherm plots of (f) Pb²⁺ (g) Ni²⁺ and (h) Sr²⁺

adsorption onto SBS in binary and ternary system: (pH = blank;

W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(f)

(g)

(h)

Figure 4.11 Temkin isotherm plots of (a) Pb²⁺ (b) Ni²⁺ and (c) Sr²⁺

adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(c)

(b)

(a)

Figure 4.11 Temkin isotherm plots of (d) RB dye and (e) MB dye adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(e)

(d)

Figure 4.11 Temkin isotherm plots of (f) Pb²⁺ (g) Ni²⁺ and (h) Sr²⁺ adsorption onto SBS in binary and ternary system: (pH = blank; W = 0.1 g; V

= 50 ml; t = equilibrium (min); and T = 30ºC)

(h) (f)

(g)

Figure 4.12 Halsey isotherm plots of (a) Pb²⁺ (b) Ni²⁺ and (c) Sr²⁺

adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

(c)

Figure 4.12 Halsey isotherm plots of (d) RB dye and (e) MB dye adsorption onto SBS: (pH = blank; W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(e)

(d)

Figure 4.12 Halsey isotherm plots of (f) Pb²⁺ (g) Ni²⁺ and (h) Sr²⁺

adsorption onto SBS in binary and ternary system: (pH = blank;

W = 0.1 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(h) (g)

(f)

Figure 4.13 Pb²⁺ adsorption kinetic plots (a) pseudo-first-order and (b) pseudo-second-order : (Co = 100-300 mg/l; pH = blank; W = 0.06 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

Figure 4.14 Ni²⁺ adsorption kinetic plots (a) pseudo-first-order and (b) pseudo-second-order : (Co = 100-300 mg/l; pH = blank; W = 0.06 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

Figure 4.15 Sr²⁺ adsorption kinetic plots (a) pseudo-first-order and (b) pseudo-second-order : (Co = 100-300 mg/l; pH = blank; W = 0.06 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)

Figure 4.16 RB dye adsorption kinetic plots (a) pseudo-first-order and (b) pseudo-second-order : (Co = 100-350 mg/l; pH = blank; W = 0.05 g; V = 50 ml; t = equilibrium (min); and T = 30ºC)

(a)

(b)