Removal of BrO3 from drinking water samples using newly developed agricultural waste based activated carbon and its determination by ultra-performance liquid chromatography-mass spectrometry Mu. Naushad*,1, Mohammad R. Khan1, Zeid A. ALOthman1, Ibrahim AlSohaimi1, Francisco RodriguezReinoso2, Turki M. Turki1, Rahmat Ali1 1 Department of Chemistry, College of Science, Bld#5, King Saud University, Riyadh, Saudi Arabia 2 Laboratorio de Materiales Avanzados, Departamento de Química Inorganica, Universidad de Alicante, Apartado 99 E-03080, Spain *Corresponding author address: Tel. 0096614674198; Email: shad81@rediffmail.com Table of content Index Captions Text S1 Text for adsorption kinetics, isotherm and thermodynamic studies. Fig. S1 N2 adsorption/desorption isotherms Fig. S2 Effect of various operating parameters on the adsorption of BrO3 by DAC (a) contact time, (b) pHi, (c) initial concentration of BrO3 and (d) temperature. Fig. S3 Regeneration studies for DAC (equilibration time 25 min; adsorbent dosage = 50 mg; volume 50 mL; initial concentration of BrO3 2 mg L-1; agitation speed 150 rpm). Fig. S4 Plots of kinetic and isotherm models for the adsorption of BrO3 by DAC (a) pseudo-first-order, (b) pseudo-second-order; (c) Langmuir isotherm and (d) Freundlich isotherm models (adsorbent dosage = 100 mg; volume 200 mL; pH 4; agitation speed 150 rpm and temperature 25 C). Fig. S5 Van’t Hoff plot for the adsorption of BrO3 onto DAC (equilibration time 25 min; adsorbent dosage = 50 mg; volume 50 mL; initial concentration of BrO3 was 2 mg L-1; agitation speed 150 rpm). Text S1. Adsorption kinetics The pseudo-first-order and pseudo-second-order equations are represented as follows: Pseudo-first-order: log qe qt log qe k1t 2.303 (1) Pseudo-second-order: (2) t 1 t 2 qt k 2 q e qe where, qt and qe are the amounts of BrO3 adsorbed at time t, and at equilibrium, respectively, k1(1/min) and k2 (g/mg.min) are the rate constants for pseudo-first-order and pseudo-second-order, respectively. Isotherm studies Adsorption isotherms describe the adsorption equilibrium between the adsorbate and adsorbent. The adsorption isotherm data are important for understanding and practical design of adsorption system. The Langmuir model is mainly applied to designate the sorption processes where no interaction between sorbate species takes place on sites, having the same sorption energies free of surface coverage. Whereas, Freundlich isothermal model is used for multilayer adsorption analysis in heterogeneous systems where adsorption heat distribution is non-uniform and adsorption is the summation result of all the active sites. The Langmuir isotherm model can be represented as: 1 1 1 qe qm bqmCe (3) Where, Ce is the equilibrium concentration of BrO3 (mg L–1); qm (mg g-1) and b (L mg-1) are the Langmuir constants associated to maximum monolayer adsorption capacity and energy of adsorption, respectively. A dimensionless equilibrium parameter (RL) has been defined to evaluate the validity of the Langmuir-type adsorption process: RL 1 1 bCo (4) Where, Co is the lowest initial concentration of BrO3ion. The RL value indicates whether the adsorption is unfavorable (RL> 1), linear (RL = 1), favorable (0 < RL< 1) or irreversible (RL = 0). Freundlich isotherm is expressed by the following equation: log qe log K f 1 log C e n (5) Where, Kf (mg/g(L/mg)1/n) and n (dimensionless) are the Freundlich isotherm constants which are indicators of adsorption capacity and adsorption intensity, respectively. The value of n is a sign of the favorability of adsorption. If the values of n1, it represent the favorable nature of adsorption. Thermodynamic studies The values of ΔG° were calculated as: G 0 H 0 TS 0 (6) where, R is a universal gas constant (8.314 J mol-1. K-1), T (K) is an absolute temperature. The values of ∆Ho and ∆So were calculated from the slopes and intercepts of the plots of lnKc versus 1/T (Figure S5) by using the following equation. H 0 S 0 ln K c RT R (7) Where Kc (L mg-1) is equilibrium constant defined as: Kc C Ae Ce (8) where, CAe (mg L-1) and Ce (mg L-1) are the equilibrium concentrations of adsorbate on solid and in solution phase, respectively. Fig S1. Fig. S2. 100 % Adsorption/Desorption % Adsorption % Recovery 95 90 85 80 75 0 1 2 3 4 Number of cycles Fig. S3. 5 6 3.5 a 1.4 2 ppm 4 ppm 2.5 4 ppm 6 ppm 2 b 6 ppm t/qt 1 log (qe-qt) 3 2 ppm 1.2 0.8 0.6 1.5 0.4 1 0.2 0.5 0 0 0 5 10 15 20 0 5 10 15 Time (min) 25 30 Time (min) 0.7 0.7 c 0.6 d 0.6 0.5 1/qe 0.5 1/qe 20 0.4 0.3 0.3 25 °C 45 °C 0.2 45 °C 55 °C 0.1 25 °C 0.2 0.1 0.4 55 °C 0 0 0 5 10 15 1/Ce Fig. S4. 20 25 0 5 10 15 1/Ce 20 25 3 ln Kc 2.5 2 2 ppm 1.5 4 ppm 6 ppm 1 0.5 0.003 0.0031 0.0032 1/T Fig. S5. 0.0033 0.0034