Methyl Orange Dye Adsorbed Biochar as a Potential Brønsted Acid Catalyst for Microwave Assisted Biodiesel Production

doi:10.21203/rs.3.rs-1872773/v1

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Methyl Orange Dye Adsorbed Biochar as a Potential Brønsted Acid Catalyst for Microwave Assisted Biodiesel Production

https://doi.org/10.21203/rs.3.rs-1872773/v1

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published 24 Jun, 2023

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Biodiesel production from non-edible oils using a highly efficient eco-friendly catalyst is a crucial requirement replacing fossil fuels. In the present work, biochar has been used for both environmental and energy applications. Using slow pyrolysis, the biochar was prepared from various biomass, mainly cassava peel, irul wood sawdust, and coconut shell. All biochars were used as adsorbents to remove an anionic dye (methyl orange) by conducting batch adsorption studies. The cassava peel based biochar showed maximum dye adsorption and was characterized using various sophisticated analytic tools, showing hydroxyl and acidic groups. Further, the dye adsorbed biochar based on cassava peel was used as a Brønsted acid catalyst for microwave assisted biodiesel production from Millettia pinnata seed oil.

Biochar

Catalyst

Adsorption

Methyl Orange Dye

Microwave

Biodiesel

Novel biochar acid catalyst prepared through methyl orange dye adsorption.
Dye adsorbed catalyst characterized by FTIR, CHNS and XPS.
Biochar based catalyst shows high activity on biodiesel production.

Recently, biochar-based heterogeneous acid catalysts have emerged as environmentally friendly, cost-effective, and highly stable for biodiesel production of non-edible oil (Konwar et al. 2014). Biochar based carbon materials can be effectively used as adsorbents to remove dyes from wastewater by adsorption (Nair and Vinu 2016). Reusing biochar after dye adsorption for biodiesel production, combining both environmental and energy applications, has much scope in heterogeneous catalysis. Acid functionalized biochars have been successfully used in our previous works as a catalyst for biodiesel synthesis, obtaining higher yield (Chellappan et al. 2018a, b, 2019).

In the present study, functionalizing biochar by adsorbing strong -SO₃H sulfonic groups through adsorption of an acid dye has been carried out to make an acid catalyst. To the best of our research knowledge, this is the first elaborate work that reports the usage of methyl orange (anionic/acidic dye) adsorbed biochar as a potential catalyst for biodiesel production from Millettia pinnata seed oil using microwave reaction.

Methyl orange (MO), (C.I.13025; C₁₄H₁₄N₃NaO₃S; MW 327.34 g/mol) was utilized for batch adsorption experiments using biochar. The three biochars (BC-CP, BC-SD, BC-CS) were prepared by the slow pyrolysis of corresponding biomass feedstocks cassava peel (CP), irul wood sawdust (SD), and coconut shell (CS), respectively.The methods are given in detail in Appendix S1.

3.1. Batch adsorption studies

The highest percentage adsorption of MO was observed for CP biochar (BC-CP) (95.3%) as compared to SD biochar (74.2%) and CS biochar (68.4%) after three hours of adsorption time at pH 2.0. The higher adsorption of BC-CP is mainly due to the higher surface area with more active sites. The zero point charge of BC-CP was estimated to be 5.9, which was higher than that of the solution pH, resulting in the dye molecule's electrostatic interaction with the biochars' adsorbent surface. The optimization for MO adsorption of BC-CP was done for different dye concentrations and pH with 0.1g of adsorbent dosage for three hours. Appendix S2 explains more details on adsorption of MO. Desorption studies were performed for three hours with deionized water to remove any unreacted dye. The kinetic model for MO adsorption was pseudo-second order, stating the presence of chemical interaction between the dye and adsorbent (Table 1a) in Appendix S4. The dye adsorbed cassava peel biochar (D-CP-SO₃H) was characterized and further utilized as a catalyst for biodiesel production using microwave reaction.

3.2. Catalyst characterization

From the elemental analysis results (Table 1b) in Appendix S4, D-CP-SO₃H shows sulfur content, indicating the presence of -SO₃H groups. The polarity (O + N/C) and aromaticity (H/C) of the catalysts determined from different atomic ratios were found to be partially influenced due to the adsorption of methyl orange. A high H/C ratio denotes lower aromaticity and carbonization degree of the biochar based catalyst, while its hydrophobic nature is due to a lower O/C ratio (Cantrell et al. 2012). A high (O + N/C) value of CP biochar denotes the presence of polar functional groups. Moreover, the molar ratios indicate that D-CP-SO₃H are less polar and hydrophobic with high aromatic nature, which is more suitable for a biochar based solid acid catalyst (Chellappan et al. 2018b).

From the FTIR spectra of D-CP-SO₃H catalyst (Fig. 1a), the adsorption peak at 3365.8 cm^− 1 is attributed to OH bond stretching. The ketonic and carbaldehyde (CO) group stretching corresponds to 1561.8 cm^− 1 and 1375 cm^− 1, respectively. The CO stretching of carboxylic acid was observed at 1000-1300cm^− 1 wavelength. From the FTIR spectra, two new peaks were observed at 1181.6 cm^− 1 and 1032.5 cm-1 wavelength, whereas no peak was observed at the 1263.6 cm^− 1. The absorbance at 1181.6 cm^− 1 corresponds to -SO₃H stretching, and absorbance at 1032.5cm^− 1 corresponds to O = S = O stretching in -SO₃H compounds. The CO bonds of carboxylic acid are replaced with -SO₃H bonds during the adsorption process (Zeng et al. 2014).

The broad XRD patterns of biochar samples compared to graphite structures are due to biochars' turbostratic nature, which is the occurrence of disorder towards a specific direction to its carbon sheets (Fig. 1b). However, the narrow definite peaks of graphite structure in the XRD patterns (C(002) and C(101)) compared to that of broader pattern denotes that the lattice network of carbon material is developed with a more orderly structure. The XRD patterns of BC-CP and D-CP-SO₃H show the same definite sharp diffraction peaks C(002) in the 2θ range of 20º-30º, indicating randomly distributed aromatic sheets of an amorphous carbon lattice structure. Comparing the weak diffraction peaks C(101) around 2θ = 35º-50º for BC-CP with D-CP-SO₃H, the latter shows slightly weaker and broad, narrow peaks, which indicates the presence of more graphitic structure after adsorption (Zeng et al. 2014).

The surface morphology of the BC-CP and D-CP-SO₃H were revealed by SEM images (Fig. 1c). The heterogeneous surface characteristics indicate cracks, rough edges, and crevices with irregular shapes. However, the BC-CP particles are much more significant as compared to D-CP-SO₃H particles. The BET analysis (Table 1b) showed that D-CP-SO₃H has a higher surface area than BC-CP, which coincides with the results obtained from the SEM images.

The surface species bonded to the D-CP-SO₃H catalyst was characterized by XPS spectra (Fig. 2). The peaks attributed to the S 2p, C 1s, and O 1s spectrums are attributed to the hydroxyl and strong sulfonic groups, explained elsewhere (Liu et al. 2013; Thushari and Babel 2018; Chellappan et al. 2019). The detailed discussion of XPS spectra intepretation is explained in Appendix S3.Thus D-CP-SO₃H proved to be the most suitable biochar based acid catalyst showing higher acid strength and acid site concentration with hydroxyl and -SO₃H groups.

3.3 Microwave-assisted biodiesel production

In the acid catalysis mechanism, an acidic proton (Brønsted acid) takes part in the reaction rather than Lewis acid due to the intense H + proton ions present in the catalyst. The strong -SO₃H groups present in D-CP-SO₃H also have strong microwave radiation absorption. The biodiesel yield of 91.25% was obtained upon batch experiment carried out at optimized parametric condition reported (Chellappan et al. 2019).

Thus, the results confirm that upon successful functionalization, the attachment of high surface density -SO₃H groups enhances the acid strength and H⁺ activity of the D-CP-SO₃H catalyst (Chellappan et al. 2018b). The catalyst's intense H + protonic acid site concentration and three functional groups (-OH, -COOH and -SO₃H) contributed much by providing the higher biodiesel yield content(Chellappan et al. 2018a). The catalyst reusability was investigated for three more cycles, and biodiesel yields % of 88.35, 82.64, and 78.47 were obtained, showing that the catalyst is relatively stable after three multiple cycles.

A new class of acid dye-modified biochar catalyst has been developed for sustainable and economic biodiesel production. The biochar based acid catalyst prepared by dye adsorption of cassava peel biochar can be used for microwave-assisted biodiesel production from Millettia pinnata seed oil. The dye adsorbed catalyst shows -SO₃H groups from the methyl orange dye molecule and other acidic groups (-OH, -COOH) which are confirmed by FTIR and XPS. A biodiesel yield of 91.25% was reported under optimum conditions. Moreover, the catalyst gave a biodiesel yield above 75% even after three runs showing good stability.

We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that all have approved the order of authors listed in the manuscript of us. We confirm that we have given due consideration to the protection of intellectual property associated with this work and that there are no impediments to publication, including the timing of publication, concerning intellectual property. In so doing, we confirm that we have followed the regulations of our institutions concerning intellectual property. We understand that the Corresponding Author is the sole contact for the Editorial process including Editorial Manager and direct communications with the office. He/she is responsible for communicating with the other authors about progress, submissions of revisions, and final approval of proofs. We confirm that we have provided a current, correct email address accessible by the Corresponding Author.

Competing Interests

The authors have no relevant financial or non-financial interests to disclose.

Funding

We are grateful for the financial assistance given by TEQIP-II sanctioned under NITC/TEQIP-II/R&D/2015-16, National Institute of Technology Calicut.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Suchith Chellappan]. The first draft of the manuscript was written by [Suchith Chellappan], [Aparna Kallingal] [Sajith Vandana], [Vaishakh Nair], [Chingakham Chinglenthoiba] and all authors commented on previous versions of the manuscript. Final review and editing was performed by [Suchith Chellappan] and [Chingakham Chinglenthoiba]. All authors read and approved the final manuscript.

Consent for publication

This manuscript has been read and approved by its all the authors and they have given the approval to submit and publish it in this journal.

Ethics approval

The research did not involve human or animal as participants, and there was no release of harmful substance to the environment as a result of the study. The authors followed the rules for good scientific practice, as described in the author guidelines.

Consent to participate

Not applicable, as there were no human participants in the study.

Availability of data and materials

All the research data used in the study are available in manuscript.

Acknowledgments

We are grateful for the financial assistance given by TEQIP-II sanctioned under NITC/TEQIP-II/R&D/2015-16, National Institute of Technology Calicut.

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Journal Publication

published 24 Jun, 2023

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Editorial decision: Major Revision
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You are reading this latest preprint version

Methyl Orange Dye Adsorbed Biochar as a Potential Brønsted Acid Catalyst for Microwave Assisted Biodiesel Production

Status:

Journal Publication

Version 1

Abstract

Figures

Highlights

1. Introduction

2. Materials And Methods

3. Results And Discussions

3.1. Batch adsorption studies

3.2. Catalyst characterization

3.3 Microwave-assisted biodiesel production

4. Conclusions

Statements And Declarations

References

Supplementary Files

Status:

Journal Publication

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