ISSN (0970-2083)

All submissions of the EM system will be redirected to Online Manuscript Submission System. Authors are requested to submit articles directly to Online Manuscript Submission System of respective journal.


G. Sowmyadevi1, Karuna Sree Merugu2*, M. Sujathai3, Naresh Kumar Katari3, D. Sirisha4

1Department of Chemistry, School of Science, GITAM Deemed to be University, Hyderabad, Telangana, India

2Department of Chemistry, School of Science, GITAM Deemed to be University, Bengaluru, Karnataka, India

3 Department of Chemistry, School of Science, GITAM Deemed to be University, Hyderabad, Telangana, India

4Department of Centre for Environment and Climate Change, Jawaharlal Nehru Institute of Advanced Studies, Hyderabad, Telangana, India

*Corresponding Author:
Karuna Sree Merugu
Department of Chemistry, School of Science, GITAM Deemed to be University, Bengaluru, Karnataka, India E-mail:

Received: 30-Jun -2023, Manuscript No. ICP-23-104414; Editor assigned: 04-Jul-2023, PreQC No. ICP-23-104414(PQ); Reviewed: 17- Jul-2023, QC No. ICP-23-104414; Revised: 20- Jul -2023, Manuscript No. ICP-23-104414 (A); Published: 03-Aug-2023, DOI: 10.4172/0970-2083.39.3.002

Citation: Sowmyadevi G, Merugu KS, Sujathai M, Katari NK, Sirisha D. A Comprehensive investigation into the removal of SO2 from aqueous medium using chemically modified Hibiscus sabdariffa as a novel adsorbent. J Ind Pollut Control. 2023;39:002.

Copyright: © 2023 Sowmyadevi G, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Visit for more related articles at Journal of Industrial Pollution Control


A green synthetic approach to synthesize HCl-treated Hibiscus sabdariffa leaf powder is used as an adsorbent to test feasibility of removing SO2 efficiency of the improved adsorbent in terms of contact duration, SO2 solution concentration and adsorbent dose. The optimized ideal conditions are 60 minutes (contact period), 1 gm (adsorbent dosage) and 20 ppm (concentration). HCl-treated Hibiscus sabdariffa leaf powder for removal of SO2 was characterized by FTIR spectroscopy.

The study assesses adsorption kinetics and isotherms in addition to the optimal circumstances of contact time, adsorbent dosage, and SO2 concentration. The outcomes show that the adsorption procedure adheres to the Temkin isotherm and the first-order kinetic model. This sheds light on the mechanism of adsorption as well as the connection between adsorbate concentration and adsorption capability. The study provides a viable approach for lowering SO2 pollution in watery environments and emphasizes the significance of using natural waste materials for environmental restoration. Overall, this study adds a thorough understanding of the potential of HCl-treated Hibiscus sabdariffa leaf powder as an efficient and long-lasting adsorbent for SO2 removal, with implications for enhanced public health and cleaner air.


Hibiscus sabdariffa, Modified, Adsorbent dosage, Batch studies, Efficiency


Sulphur dioxide has a subliminal leak of is occurring into the atmosphere. Human respiratory systems are adversely affected by SO2, leading to respiratory diseases. Our plants, natural systems, and manufactured materials have suffered due to human activity and other methods. Numerous statistical studies demonstrate that SO2 pollution impacts many urban areas and that there is a strong correlation between respiratory diseases and SO2 levels (Chen, et al., 2021; Song, et al., 2014; Elder, et al., 2018; Razmkhah, et al., 2020; Hao, et al., 2019). Because of the complex topography of the Deccan Plateau in southern India, air flow systems are altered, and the twin cities of Hyderabad's air pollution are affected by distinct directional qualities or flow patterns. Topography considerations should include while assessing air pollution statistics from the pollution control board. Land cover taken into account when attempting to assess the circumstances of cities (Lee, et al., 2016; Zhang, et al., 2020; Guo, et al., 2021; kang, et al., 2020; Xu, et al., 2021; Zhang, et al., 2019).Urbanization, industrialization, mixed traffic, and industrial emissions are examples of human-caused sources of NOx and SOx pollution in cities.According to earlier investigations, industrial complexes in cities have allegedly polluted the city (Li, et al., 2018; Yi et al., 2014; Tailor, et al., 2014; Si, et al., 2019; Wang, et al., 2021; Ahiduzzaman, et al. 2021).In this regard, adsorption factors like duration, concentration, and dosage have been used in adsorption studies to develop and control technology for controlling SO2 pollution and an aqueous solution of SO2 by using green absorbent (Hibiscus sabdariffa).

Considering the need to reduce the SO2 in natural sources like aqueous medium, a natural adsorbent is prepared from abundantly available Hibiscus sabdariffa leaf powder (non-conventional and biodegradable). Hibiscus sabdariffa is a novel adsorbent for adsorption of SO2 from aqueous solutions. FTIR studies and control technology developed for controlling SO2 pollution and aqua solution of SO2 by using green absorbent, which is widely grown Hibiscus sabdariffa (Ahiduzzaman, et al. 2021; Jeffery, et al., 2021). In these current studies, adoption studies have been carried out with adsorption parameters such as time concentration dosage and temperature. FTIR studies to develop and control technology for controlling SO2 pollution and aqua solution of SO2 by using green absorbent which is widely grown in India, namely Hibiscus sabdariffa leaf powder.

Materials and Methods

Sodium metabisulphite, para-rosaniline purchased from Sigma Aldrich.and Formaldehyde, Mercurous chloride,and HCl, from Sisco Research Laboratories (SRL). All the reagents of analytical grade and deionized water used for the preparation of all the aqueous solutions.


We investigated HCl-treated Hibiscus sabdariffa leaf powder’s optical properties with a UV–Visible spectrophotometer (UV 1800, Shimadzu, Japan).To investigate the functional groups of the HCl-treated Hibiscus sabdariffa leaf powder, Fourier-Transform Infrared (FT-IR) Bruker ATR-FTIR, U.S.A. Experiments are carried out in triplicates.

Adsorbent Preparation from Hibiscus sabdariffa

Hibiscus sabdariffa leaves are collected from our house garden as cultivated there. The leaves are air dried, sun dried and powdered using a domestic blender. Then the powder is stored in airtight container for future use and after which it is treated with 0.1 N HCl and further dried.

Preparation of standard samples

In 1000 mL standard flask, 15 gms of sodium meta bisulphites is dissolved in deionized water to prepare a 1000 ppm stock solution. Appropriate quantities to prepare working standards, to get the desired concentration of SO2 from the stock solution.

Experimental Procedure for Percentage Removal of SO2

The west gaeke method treats the prepared working standards with green adsorbent HCl-treated Hibiscus sabdariffa. Batch adsorption experiments are carried out concerning contact time (10,20,30,40,50,60 (in min)), SO2 concentration (20,40,60,80,100 (ppm)) and adsorbent dosage (0.5,1.0,1.5,2.0 (in gm)) for the removal of SO2. The initial and final concentrations of SO2 color determined using the color compatibility method by the West-Gaeke method. Uv-Vis Spectrophotometer recorded the Percentage removal of SO2. HCl-treated Hibiscus sabdariffa leaf powder how effective is at removing SO2 from aqueous solutions is calculated with this equation


Where (SO2) f=Final concentration after adsorption

(SO2) i=Initial concentration before adsorption.

Results and Discussion

FT-IR Analysis of Hcl-Treated Hibiscus Sabdariffa Leaf Powder Treated with Hcl for Adsorption Capacity

For adsorption studies, consider functional group analysis. Figs. 1 and 2 show FT-IR spectra for SO2 removal, illustrating the adsorbent behavior before and after adsorption. Aliphatic amines(R-NH2), Carbonyl( >C=O), C-H and C=C (Benzene) functional groups at 2998.80, 2936.89, 2872.54 (concerning R-NH2) and many peaks were smoothened in the range of 2330-3000cm-1 indicating the participation of adsorption by lysine, phenols, flavanoid, lysine groups. The carboxylic acids and acid groups also participate in the adsorption of NO2 molecules. The decrease in the intensity of the peaks in 1790.16 to 1738.68 cm-1,1780.66 cm-1 to 1657.18 cm-1, 1634.30 cm-1 to 1521.35 cm-1 indicates the involvement of aromatic and aliphatic amines and carbonyl groups. There is a tremendous change in the finger print region of FTIR.


Figure 1: FTIR of HCl-treated Hibiscus sabdariffa leaf powder before adsorption.


Figure 2: FTIR of HCl-treated Hibiscus sabdariffa leaf powder after adsorption.

Betacyanin pigment in leaf extract has been decreased i.e in the range of 1653.918 cm-1 is not observed after adsorption, indicating protonated molecular form Betalanine and participated in the adsorption of NO2 molecules.

Efficiency Studies of Hcl-Treated Hibiscus Sabdariffa Leaf Powder Dosages as Adsorbent for SO2

We carried out batch adsorption studies with 0.5 gms to 2 gms of chemically treated Hibiscus sabdariffa leaf powder for the initial concentration of aqueous solution of SO2 (Table 1). Fig. 3 shows the removal of SO2 ions with various doses of chemically treated Hibiscus sabdariffa leaf powder, with a dosage optimum of 1.0 gm. The percent removal of SO2 ions decreased from 1.0 gms to 2.0 gms as the dose increased, indicating that the optimal dose of 1.0 gm.

HCl-treated Hibiscus sabdariffa (60 mins, 20 ppm).
Adsorbent dosage 0.5 1 1.5 2
OD 0.2 0.05 0.07 0.09
Final concentration 30 7 10 13
% Removal 25 82.5 75 67.5

Tab.1. Batch adsorption studies for the dosage of the adsorbent.


Figure 3: Effect of HCl-treated Hibiscus sabdariffa leaf powder dosages on % removal of SO2. Note: % Removal.

Efficiency Studies of Hcl-Treated Hibiscus Sabdariffa Leaf Powder With Contact Time Adsorbent for SO2

A 20 ppm aqueous SO2 solution with 1 gm of HCl-treated Hibiscus sabdariffa leaf powder was used to determine the time intervals (Table 2).

HCl-treated Hibiscus sabdariffa(20 ppm, 1gm Adsorbent)
Contact time 10 20 30 40 50 60
OD 0.26 0.24 0.2 0.16 0.14 0.05
Final concentration 39 37 30 24 20 7
% Removal 2.5 7.5 25 40 50 82.5

Tab.2. Batch adsorption studies with respect to the dosage of the adsorbent.

As seen in Fig. 4 the percent elimination increased as contact time increased, with 60 minutes being the optimum contact time with maximum of 82.5% SO2 removal from aqueous solutions.


Figure 4: Effect of HCl-treated Hibiscus sabdariffa leaf powder adsorbent contact time on % removal of SO2.equation Removal

Influence of Concentration of Working Standard Solution on Removal Percentage of SO2

With different starting concentrations (ppm) of 20,40,60,80,100 prepared batch experiments (Table 3). As shown in Fig. 5 the percent elimination was 95% at 20 ppm, 82.5 at 40 ppm, and there after declined, indicating acidified Hibiscus sabdariffa leaf powder exhaustion (Nenavath Gandhi, et al., 2012).

HCl-treated Hibiscus sabdariffa (60 mins, 1gm Adsorbent)
Initial concentration 20 40 60 80 100
OD 0.01 0.05 0.1 0.14 0.22
Final concentration 1 7 14 20 33
% Removal 95 82.5 76.6 75 67

Tab.3. Batch adsorption studies for the concentration of working standard solution on removal percentage of SO2.


Figure 5: Effect of concentration of working standard solution on removal percentage of on % of SO2equation

Adsorption Isotherms

The critical factor influencing the adsorption of SO2 molecules by Gongura is temperature. We conducted studies at 20°C, 40°C, 60°C and 80°C and the results by using Langmuir, Freundlich, and Temkin isotherm, shown in Figs 1-3. And adsorption constants are in the Table 4.

S. No Parameters Temperature (°C)
    20°C 40°C 60°C 80°C
  Langmuir adsorption isotherm
1 R2 0.7998 0.9617 0.9037 0.9969
Q0 1.095 1 1 1.046
b2 0.02 0.0047 0.0062 0.0065
  Freundlich adsorption isotherm
2 Log K 0.8795 0.8155 0.7693 0.775
R2 0.9981 0.9974 0.9936 0.9965
1/n 0.2287 0.2125 0.2659 0.234
  Temkin adsorption isotherm
3 R2 0.9975 0.988 0.9815 0.9885
a 0.745 0.62 0.55 0.52
b 3.9 7.7 8.8 8.7

Tab.4. Adsorption isotherm constants.

The R2 values are high in the case of Freundlich and Temkin adsorption isotherms ranging from 0.775-0.8795 and 0.9885-0.9975 respectively. The data indicates that it is not following Langmuir adsorption isotherm. The log K values of Freundlich adsorption isotherm decrease with an increase in temperature, showing the lower temperature is favourable (Figs 6 and 7). Adsorption intensity is high at lower temperatures and adsorption capacity is increasing due to the trend indicating the behaviour of adsorption is changing from physical to chemical adsorption. Temkin adsorption isotherms are showing similar results. The bio-charring behaviour of the Gongura provides a large surface area after thermal modification. Adsorption intensity decreases with an increase in temperature (Figs 8 and 9).


Figure 6: The graph represents Qe vs. Ce .equationequation


Figure 7: The graph represents log Qe vs. log Ce. equationequation


Figure 8: The graph represents Ce/Qe vs. Ce. equationequation


Figure 9: The graph represents %removal vs. Ce.equationequation

Adsorption kinetics

R2 values of pseudo-first-order kinetics is greater than pseudo-second-order kinetic model, which indicates adsorption process is following first order (Table 5).

The experimental data determined pseudo first order and pseudo second order kinetics.
S. No Parameters at 20 micro gm/lit at 40 micro gm/lit at 60 micro gm/lit at 80 micro gm/lit
1 Pseudo first order kinetics model
R2 0.9632 0.9656 0.958 0.9332
K 1.377 1.64 1.801 1.927
2 Pseudo second order kinetics model
R2 0.771 0.8302 0.7725 0.8671
K 0.04622 0.05006 0.07646 0.05059
3 Elovich midel
R2 0.9806 0.9517 0.928 0.918
Alpha 3.171 3.1 3.024 3.014
Beta -13 -19.67 -21.6 -23.17
4 Intra particulate diffusion model
R2 0.9806 0.9517 0.928 0.918
K 0.2231 0.3491 0.4212 0.4505

Tab.5. The description process is based on the sorbent physical, chemical properties and mass transfer.

In Elovich model R2 values are ranging from 0.9034-0.7508 at different concentration. The slope (alpha) values are decreasing with increase in concentration (Figs. 10 and 11). Similarly, beta values are also decreasing which are represented by positive and negative values respectively. Similarly inter particle diffusion R2 values are high compared to Elovich model (Figs. 12 and 13).


Figure 10: The graph represents log Qe-Qt vs T(Time in mins). equationequation


Figure 11: The graph represents T/Qt vs. T(Time in mins). equationequationequation


Figure 12: The graph represents Qt vs. ln (T). equationequation


Figure 13: The graph represents % Removal vs. t(1/2) .equationequationequation

The experimental data fits Inter particle diffusion model and Pseud- first-order kinetic model.


HCl-treated Hibiscus sabdariffa leaf powder were successfully employed as adsorbent for removal of SO2 from aqueous solutions. The degree of SO2 removal by HCl-treated Hibiscus sabdariffa leaf powder increased with increasing contact time, with 60 minutes being found to be the optimum. The percent removal of SO2 declined as the concentration increased, with the greatest percent removal occurring at 20 ppm, and greater percent SO2 removal was achieved using a 1.0 gm adsorbent dose. The use of plant waste is a critical advance in preserving a sustainable environment. The quality of our natural resource. Such as air and water, can be improved by employing these low-cost, environmentally friendly biosorbents. It follows temkin isotherm and first order kinetics.


Copyright © 2024 Research and Reviews, All Rights Reserved