SORPTION OF DIRECT DYES SORPTION OF DIRECT DYES FROM AQUEOUS SOLUTION ONTO FROM AQUEOUS SOLUTION ONTO A SYNTHETIC ADSORBENT. A SYNTHETIC ADSORBENT. KINETIC STUDY KINETIC STUDY Simona Gabriela Muntean 1 , Sergiu Coseri 2 , Georgeta Simona Gabriela Muntean 1 , Sergiu Coseri 2 , Georgeta Simu 3 , Oana Paska 1 Simu 3 , Oana Paska 1 Institute of Chemistry Timisoara of Romanian Academy, 24 B-dul Mihai Viteazul, 1 Institute of Chemistry Timisoara of Romanian Academy, 24 B-dul Mihai Viteazul, 1 300223 Timisoara, Romania; 300223 Timisoara, Romania; 2 "Petru Poni" Institute of Macromolecular Chemistry, 41A Grigore Ghica Voda Alley, "Petru Poni" Institute of Macromolecular Chemistry, 41A Grigore Ghica Voda Alley, 2 Iasi, 700487, Romania Iasi, 700487, Romania University of Medicine and Pharmacy “V. Babeş” Timiş şoara, Faculty of Pharmacy, oara, Faculty of Pharmacy, 3 University of Medicine and Pharmacy “V. Babeş” Timi 3 Eftimie Murgu 2, 300041 Timişoara, Romania Eftimie Murgu 2, 300041 Timişoara, Romania e-mail: sgmuntean@acad-icht.tm.edu.ro e-mail: sgmuntean@acad-icht.tm.edu.ro
Introduction Introduction Industries such as textile, paper, plastics, etc., use great quantities of water, and chemical substances, for coloring the manufactured articles, and discharge large amounts of wastewater during industrial processing. The discharge of coloured wastewater is a major environmental concern (can produce serious pollution problems) due to their poor biodegradability, carcinogenicity and toxicity. The adsorption process provides an attractive alternative for the treatment of dye contaminated waters because of its simplicity, selectivity and efficiency.
Aim Aim To determine the efficiency of copolymer microbeads, as adsorbent for removal of direct dyes from aqueous solutions To study the influences of process variables: contact time, and initial concentration on the adsorption. The kinetics study of the adsorption of direct dyes onto adsorbent.
Experimental Experimental Molecular structure of the studied direct dyes H 3 C N N CH 3 N N CO NH H N NH N O O N C 6 H 4 SO 3 H C 6 H 4 SO 3 H OD OD HOOC OH NH 2 H O N N CONH N N N N NO 2 HO 3 S SO 3 H GD The chemical structure of investigated copolymer ( StDVBNMe ) CH 2 N + (CH 3 ) 3 Cl - R R: styrene-divinylbenzene copolymer
Method Method Experimental study • Dye concentration: 10 -5 ÷ 10 -4 M; • Adsorbent dose 100mg/100mL; • Temperature: 25 o C; • Solution pH: 7.11. The amount of dye adsorbed − ⋅ ( C C ) V = 0 t q t W q t : amount of dye adsorbed onto the copolymer unit at time t (mg/g), C 0 and C t : dye concentration in solution at initial time, and at time t (mg/L), V: solution volume (L), W: amount of copolymer (g) The percentage of dye removal ( η ) − C C η = × 100 0 e C 0 C e : dye concentration at equilibrium (mg/L).
Results and Discussions Results and Discussions Characterization of copolymer microbeads Characterization of copolymer microbeads (a) (b) (c) Fig. 1. Samples of: (a) StDVBNMe ; (b) OD - StDVBNMe; (c) GD - StDVBNMe . (c) (b) (a) Fig. 2. SEM images for: (a) StDVBNMe ; (b) OD - StDVBNMe ; (c) GD – StDVBNMe.
Effect of initial dye concentration and agitation time Effect of initial dye concentration and agitation time 80 OD GD 80 70 70 60 60 50 50 t (mg/g) t (mg/g) 40 40 q q 30 30 10 mg/L 8 mg/L 45 mg/L 40 mg/L 20 20 90 mg/L 80 mg/L 10 10 0 0 0 50 100 150 200 250 0 50 100 Time (min) Time (min) (b) (a) Fig. 3. Effect of contact time and dye concentration on the percentage removal of dyes (a. OD , b. GD ). Conditions : pH 7.11; T = 25 ± 1 o C, agitating speed 250rpm. Table 1. Amount and percentage of dyes adsorbed Dye Dye concentration q e t e η (mg/L) (%) (mg/g) (min) 8 7.66 35 99.05 OD 40 39.11 75 98.13 80 77.32 90 97.99 10 9.07 65 98.53 GD 45 42.02 130 89.47 90 81.48 205 88.47
Adsorption kinetics The first-order Lagergren model ( ) k − = − log q q log q 1 t e e 2 . 303 The pseudo-second-order kinetic model t = 1 + 1 t q 2 q k q e 2 e q e , q = amount of dye adsorbed on adsorbent at equilibrium, and any time t , respectively (mg g -1 ). k 1 = the Lagergren rate constant of first order adsorption (min -1 ) k 2 = the equilibrium rate constant of second-order adsorption (g mg -1 min -1 )
Fig. 4. First-order-kinetics plots of the experimental data for the adsorption of OD and GD onto StDVBNMe GD 2.0 OD 2 =0.9627 2 2 =0.9132 8 mg/L; R 10 mg/L; R 2 =0.9658 2 =0.9102 40 mg/L; R 1.5 45 mg/L; R 2 =0.9895 2 =0.9441 1 80 mg/L; R 90 mg/L; R 1.0 0 t ) e -q 0.5 t ) e -q log(q log(q -1 0.0 -2 -0.5 -3 -1.0 -1.5 -4 0 50 100 150 200 250 0 50 100 150 200 250 300 Time (min) Time (min) Fig. 5. Second order plots for the adsorption of OD and GD onto StDVBNMe 25 GD OD 20 20 2 =0.9999 2 =0.9956 15 8 mg/L; R 10 mg/L; R 2 =0.9978 2 =0.9971 15 40 mg/L; R 45 mg/L; R 2 =0.9993 2 =0.9939 80 mg/L; R 90 mg/L; R t/q t t/q t 10 10 5 5 0 0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 400 Time (min) Time (min)
Table 4. Comparison of experimental and calculated qe values; first order and second order adsorption rate constant for the adsorption of OD and GD dyes Dye Initial dye q e (exp) First order kinetic model Second order kinetic model concentration (mg/g) q e (calc) k 1 x 10 2 (min -1 ) q e (calc) k 2 x 10 2 (mg/L) (mg/g) (mg/g) (g mg-1 min-1) 8 7.66 2.09 5.645 7.72 11.47 OD 40 39.11 20.65 2.303 41.27 0.244 80 77.32 35.6 2.309 80.26 0.134 10 9.07 6.31 3.418 9.84 0.773 GD 45 42.02 28.95 1.985 45.81 0.096 90 81.48 79.47 1.808 83.81 0.026
Conclusions The removal of two dyes namely OD , and GD from aqueous solution by StDVBNMe was found to be effective. The StDVBNMe microbeads can by used as a adsorbent in adsorption process in low costs working conditions (room temperature, pH ~ 7). The adsorption process for OD , and GD dyes removal, can be described by the pseudo-second order kinetic model.
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