SUPPLEMENTARY INFORMATION SHEET

Facile synthesis of TiO2-PC composites for enhanced photocatalytic abatement of multiple

pollutant dye mixtures: A comprehensive study on the kinetics, mechanism and effects of

environmental factors

Priyanshu Verma, Sujoy Kumar Samanta*

Department of Chemical and Biochemical Engineering,Indian Institute of Technology Patna, Bihta, Patna – 801106 (India)

*Corresponding author E-mail address: sksamanta@iitp.ac.in

S1. Details of instruments used for catalyst characterization:Instrument Company/ Manufacturer Model Conditions

SEM TESCAN VEGA3 LMUHV: 30.0 kV at different

magnifications.

EDX TESCAN + BrukerTescan VEGA3 LMU with

energy-dispersion spectrometer (EDS) Bruker XFlash detector

HV: 30.0 kV

TEM JEOL JEM 2100 HV: 200.0 kV at 20000x magnification.

XRD Rigaku TTRX-IIICuKα (1.542 Å) radiation;

2θ range: 10-80°; Scan rate: 2°/min; Scan step 0.02°.

PL Perkin ElmerLS 55

Fluorescence spectrometer

Excitation@200 nm. The fluorescence was recorded

between 300-650 nm.

BET/N2 IsothermQuantachrome

InstrumentsNOVA-1000 Ver. 3.70

The samples were degassed at 500 °C for 12 hrs. Multiple N2

adsorption and desorption points were recorded between the

relative pressure range of 0.020–0.992 at 77.4 K.

TGA Perkin Elmer STA 6000Heat from 30 °C to 950 °C at the

rate of 20 °C/min under continuous N2 flow @ 20 ml/min.

UV-Visible Spectrophotometer

Thermo Scientific EvolutionTM 200 series1.5 mg of photocatalyst was

dispersed in 5 ml of Millipore water before analysis.

CHNS Elementar vario MICRO cubeAt high temperature in the oxygen rich environment using Helium as

inert carrier gas.

1

S2. Digital photocatalytic reactor used in this study:

A self customized batch photocatalytic reactor was used in this study. This reactor basically has

two parallel UV-rods (PHILIPS TUV 11W G11 T5, a cylindrical low pressure Hg lamp with

irradiation area about 96.94 cm2). It also contains one hot plate cum magnetic stirrer and a

temperature probe inside a perfectly dark enclosure to avoid the surrounding lights and internal

reflections. The reaction vessel used was a beaker with diameter and top exposed area of 50 mm

and ca. 19.63 cm2, respectively. The photometric data of UV source or lamp have been shown in

Fig. S1(a). The UV fluence rate was measured with the help of EIT UV Power Puck® II

Radiometer and was found about 4.918 mW/cm2 (UV-C) at the surface of the single low pressure

Hg lamp. The schematic of the reaction setup is given in Fig. S1(b).

Fig. S1 (a) Emission profile of the low pressure Hg lamp (UV lamp).

Fig. S1 (b) Schematic of the batch photocatalytic reactor.

2

S3. Reaction conditions used to study the influence of different environmental factors:

Variable Factors (3 Level) Other Factors UV Exposure*

Salt Concentration

(NaCl)

1 g/lVolume: 5 ml of Mixed Dyes;Catalyst Dose: 1 mg/ml;Stirring/Mixing Speed: 500 RPM;pH: Neutral; Ambient Temperature: (24 ± 2 °C);Chemical Oxidants: None;Reactor Design Parameters: Fixed or Constant

30 min5 g/l

10 g/l

pH Buffer

pH 4.0Volume: 5 ml of Mixed Dyes;Catalyst Dose: 0.5 mg/ml;Stirring/Mixing Speed: 500 RPM;Ambient Temperature: (24 ± 2 °C);Chemical Oxidants: None;Salts and Additives: NoneReactor Design Parameters: Fixed or Constant

150 minpH 7.0

pH 9.2

Temperature

25 °CVolume: 5 ml of Mixed Dyes;Catalyst Dose: 1 mg/ml;Stirring/Mixing Speed: 500 RPM;pH: Neutral; Chemical Oxidants: None;Salts and Additives: NoneReactor Design Parameters: Fixed or Constant

15 min35 °C

45 °C

Stirring/Mixing Speed

100 RPMVolume: 5 ml of Mixed Dyes;Catalyst Dose: 1 mg/ml;pH: Neutral; Ambient Temperature: (24 ± 2 °C);Chemical Oxidants: None;Salts and Additives: NoneReactor Design Parameters: Fixed or Constant

15 min500 RPM

1000 RPM

Catalyst Dose

0.5 mg/mlVolume: 5 ml of Mixed Dyes;Stirring/Mixing Speed: 500 RPM;pH: Neutral; Ambient Temperature: (24 ± 2 °C);Chemical Oxidants: None;Salts and Additives: NoneReactor Design Parameters: Fixed or Constant

15 min1.0 mg/ml

1.5 mg/ml

*UV Exposure time duration was varied due to different observed degradation speed of mixed pollutant dyes in each instance.

3

S4. Signature spectrum of different pollutant dyes used in this study:

Fig. S2 represents the individual dye’s UV-Visible absorption spectrum in the scan range of 200

to 750 nm. In this figure, individual λmax has been identified and considered as 667 nm, 553 nm,

518 nm and 466 nm for MB, RhB, Amaranth and MO, respectively. The absorbance at

individual λmax has been calibrated as the remaining concentration of the respective pollutant dye

in a synthetic pollutant dye mixture.

Fig. S2 UV-Visible absorption spectra of individual pollutant dyes.

The percentage removal of individual pollutant dye can be calculated using the given formula:

Removal∨decomposition∨degradation percentage=CO−C t

CO∗100(%)

Where, CO is the initial concentration or absorbance at λmax of individual pollutant dye and C t is

the concentration or absorbance at λmax of individual pollutant dye at time ‘t’.

4

S5. Degradation kinetic analysis:

The kinetic data of photocatalytic degradation of individual pollutant dye in a synthetic pollutant

dye mixture using TiO2 and TiO2-PC photocatalysts were analyzed using a pseudo-first-order

kinetic model which was proposed by Langmuir–Hinshelwood and is as follows:

dCdt

=−kC

Where C represents the concentration of individual pollutant dye in a synthetic pollutant dye

mixture at time ‘t’, and ‘k’ is the apparent degradation rate constant. The integration of above

equation yields:

ln (CO

C )=kt

Plotting ln(C0/C) as a function of time yields the ‘k’ values. Here, C0 is the initial concentration

of individual pollutant dye in a synthetic pollutant dye mixture. A linear relation between

ln(C0/C) and ‘t’ was observed in the Fig. 8. Then, the individual pollutant dye’s ‘k’ value for the

photocatalytic degradation of synthetic pollutant dye mixture using TiO2 and TiO2-PC

photocatalysts were determined graphically; they are listed in Table 1. The agreement between

experimental data and the results obtained using the pseudo-first-order kinetic model was

evaluated from the coefficients of determination (R2). The high values of R2 in most of the cases

revealed that the photocatalytic degradation of individual pollutant dyes in a mixed synthetic

pollutant dyes matrix using TiO2 and TiO2-PC photocatalysts obeyed the pseudo-first-order

kinetic model. In addition, the first half life of individual pollutant dye was calculated using a

given formula:

t 1/2=0.693

k

5

S6. Characterization results:

E

6

Fig. S3 EDX spectrum of TiO2, PC and TiO2-PC composite.

Fig. S4 EDX map of TiO2-PC nano-micro composite.

Fig. S5 TEM image of bare-TiO2 nanoparticles used for the preparation of TiO2-PC nano-micro composites.

7

Fig. S6 PL patterns of bare-TiO2, PC and TiO2-PC nano-micro composite.

Fig. S7 (a) UV-Visible absorption spectra of bare-TiO2 and TiO2-PC nano-micro composite and (b) Band gap measurement using the Tauc plot method.

8

S7. Visuals of mixed synthetic pollutant dyes matrix during photocatalytic degradation:

Fig. S8 Initial synthetic pollutant dye mixture (a); Dye mixture+TiO2-PC (b) and Dye mixture+TiO2 (c), after 30 mins of dark stirring; UV photolysed (4 hr) initial synthetic pollutant

dye mixture (d).

Fig. S9 Synthetic pollutant dye mixture treated with bare-TiO2: Here, 1, 2, 3, 4, 5, 6 and 7 show the degraded samples after 30, 60, 90, 120, 150, 180 and 240 min, respectively.

Fig. S10 Synthetic pollutant dye mixture treated with TiO2-PC: Here, 1AC*, 2AC, 3AC, 4AC, 5AC, 6AC and 7AC show the degraded samples after 30, 60, 90, 120, 150, 180 and 240 min,

respectively.

*Note: ‘AC’ basically indicates ‘added processed carbon (PC)’.

9

10

Fig. S11. Mass spectra of: (a) Initial; (b) bare-TiO2 treated; (c) TiO2-PC treated synthetic pollutant dye mixtures.

S8. Effect of different PC weight fractions on photocatalytic activity of TiO2-PC composites:

Fig. S12 RhB degradation performance of TiO2-PC composites with different PC weight fractions (Catalyst dose= 1 g/l; Reaction volume= 10 ml; RhB concentration = 5 ppm; UV-C

irradiation= 1 h).

11