Today, we are joined by Ragavan Chandrasekar, a rising expert in sustainable water treatment and a true innovator who is transforming waste into robust biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More solutions.

Ragavan is a Prime Minister’s Research Fellow at the Indian Institute of Technology Guwahati, India. His research is at the forefront of sustainable water treatment, focusing on the innovative transformation of plant-based biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More into functional biochar and hydrochar. He develops green, low-cost, and highly efficient biochar-based adsorbents that tackle the critical challenge of emerging contaminants in water without relying on harmful chemicals or energy-intensive processes.

His work is distinguished by its use of diverse synthesis routes to tailor the structural and surface properties of these composites. Ragavan’s research has consistently elucidated the biochar-based adsorption mechanisms for pollutants and demonstrated excellent selectivity and reusability, even in complex multicomponent systems.

Through his comprehensive research, Ragavan Chandrasekar is bridging the gap between fundamental carbon material engineering and real-world environmental applications. His expertise is further evidenced by an extensive publication record, recognition as an award-winning presenter at international conferences, and his contributions as a reviewer for leading scientific journals.

Welcome, Ragavan. I am pleased to have you here to share your insights with the Biochar Today community.

Shanthi Prabha : Ragavan, your journey into the world of biochar and hydrochar, particularly for tackling water contaminants, is truly inspiring. Could you share what initially sparked your interest in this field and how your PhD journey evolved into a focus on sustainable biomass transformation?

Ragavan Chandrasekar: Thank you! I’ve always been someone who values sustainability over the mere fascination of science. I believe science should serve society, solving problems, not just be inspiring. In a PhD journey, you need freedom of thinking to explore any research area, in this aspect, I feel lucky with my PhD supervisor, Dr. Selvaraju Narayanasamy (Associate Professor, IIT Guwahati). My journey into research started with a deep curiosity for exploring how things work, and this interest was strengthened by my Bachelor’s dissertation mentor, Dr. V C Padmanaban (currently working as Assistant Professor, NIT Agartala), who instilled in me a sense of purpose in applying engineering toward environmental sustainability. Not to mention, my PhD path naturally evolved as I realized the unexplored potential of biomass residues in transforming polluted water systems. From there, converting waste into solutions through biochar and hydrochar became a mission rather than a research topic.

SP: You’ve explored various biochar synthesis routes, from pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More to nitrogen doping and bentonite impregnation. What has been the most surprising or unexpected discovery you’ve made while experimenting with these different modification techniques for biochar and hydrochar?

RC: As you rightly pointed out, we’ve explored several modification strategies to enhance the performance of both biochar and hydrochar. One of the most surprising outcomes came from combining nitrogen doping with bentonite impregnation during pyrolysis. This synergy significantly altered the surface chemistry of the resulting biochar. The doped nitrogen introduced electron-rich functional groups, while bentonite, being a clay mineral, added structural complexity and active sites. Together, they enhanced the material’s ability to interact with versatile organic contaminants, especially complex dye molecules, through mechanisms such as electrostatic interaction, hydrogen bonding, and π–π stacking.

In contrast, when we switched to catalytic hydrothermal carbonization (HTC), a lower-temperature aqueous-phase carbonization process, we observed a distinct behavior in hydrochar. Unlike pyrolytic biochar, the hydrochar exhibited amphiphilic characteristics, meaning it had both hydrophilic and hydrophobic regions. This dual nature enabled it to interact selectively with organic contaminants based on their hydrophobicity and hydrogen bond donor or acceptor capacity. For instance, hydrophobic compounds were preferentially adsorbed due to van der Waals interactions, while polar compounds interacted via hydrogen bonding with surface oxygen or nitrogen functionalities. This selective interaction is not commonly observed in traditional pyrolytic biochars, making HTC-derived hydrochar particularly promising for treating mixed contaminant wastewaters.

We further advanced this approach by engineering hydrochar with dual heteroatom doping, such as nitrogen and sulfur, specifically designed for catalytic advanced oxidation processes (AOPs). These dopants enhanced the redox reactivity of hydrochar, allowing it to activate peroxymonosulfate (PMS) (an oxidant) and generate reactive radicals such as SO₄•⁻ and •OH efficiently. Initially, we expected only incremental improvements in degradation performance. Surprisingly, the combination of heteroatomic sites, surface functionality, and catalytic activity led to a significant acceleration in degradation kinetics, especially for the complex diazo benzidine dye like Direct Blue-6, which is a carcinogenic aqueous contaminant and commonly used for dying fabrics

These findings highlight how small atomic-level modifications, whether in the form of surface functional groups or heteroatom dopants, can drive large-scale improvements in pollutant removal. It highlights the importance of rational material design in developing next-generation adsorbents and catalysts for sustainable water treatment.

SP: One of the most promising aspects of your research is the demonstrated selectivity of your biochar and hydrochar adsorbents in complex multicomponent systems, maintaining high removal efficiencies for priority contaminants. This is a significant step towards real-world application. What do you believe are the biggest hurdles in scaling up these selective adsorbents for industrial use?

RC: The biggest hurdles include the variability of real wastewater, cost-effective regeneration, and consistency in large-scale production. In real-world scenarios, biochars often face complex mixtures of competing ions and organics, which can suppress selectivity. Additionally, industries seek adsorbents that are not only selective but also regenerable over multiple cycles. So, ensuring scalability while maintaining high performance, structural integrity, and eco-safety remains a technical and economic challenge.

SP: You’ve successfully engineered biochar from sawdust and other plant-based biomass. For those considering feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More options, what are the most critical factors you evaluate when selecting biomass for biochar production aimed at specific contaminant removal, and how do these factors influence the final material’s properties and performance?

RC: Our primary goal is to utilize green and locally available waste materials. To be specific, we focus on valorizing industrial waste like sawdust, lignocellulosic pods, and, more recently, cattle manure. Each biomass type contributes uniquely. For instance, in lignocellulosic feedstocks, lignin content influences carbon yield, and cellulose governs porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More. Furthermore, certain biomass contains heteroatoms, which eliminates the addition of an external doping agent and aids in the development of efficient catalysts.

For those who are not familiar with the chemistry of materials, heteroatoms with a significant electronegativity difference from carbon can act as active centres for oxidant activation in advanced oxidation processes and help in Lewis acid-base interaction in adsorption.

Practically speaking, for large-scale applications, it should be ensured that the feedstock is available throughout the year, and if it is rich in heteroatoms (ex, cattle manure) it would be more appropriate for adsorption and catalytic applications.

SP: Many of our readers are interested in the practical application of biochar. Beyond laboratory settings, what are some of the biggest challenges you foresee in translating your highly efficient biochar and hydrochar solutions for emerging contaminants into large-scale, cost-effective water treatment systems, especially in diverse geographical and economic contexts?

RC: Scaling up biochar-based water treatment systems comes with several practical challenges. First, making these systems affordable in low-resource areas is difficult, especially where infrastructure is limited. There is also a need to ensure that the biochar produced meets consistent quality standards and passes regulatory checks for safe use. Even if biochar performs well in the lab, real-world use depends on whether it can be regenerated and reused easily, without causing environmental harm. To make biochar solutions truly practical, they must also be designed to fit different local conditions, whether urban or rural, and be simple enough to operate and maintain in diverse settings.

SP:The concept of “reusability” is vital for the sustainability of any adsorbent. Could you elaborate on the methods you employ to regenerate your biochar and hydrochar materials, and what are the trade-offs between regeneration efficiency, cost, and the potential for secondary pollution?

RC: Alkaline/acid washing, thermal reactivation, and oxidant-based treatments are commonly employed methods for regenerating spent biochar. Among these, oxidant-based regeneration using agents such as hydrogen peroxide or peroxymonosulfate offers an effective means to restore adsorptive properties without significant damage to the biochar structure. These oxidants help degrade or remove retained contaminants from the surface. Compared to thermal regeneration, which is energy-intensive, and alkaline/acid washing, which may not fully recover performance, oxidant-based methods provide a more balanced and efficient approach. However, careful optimization of oxidant concentration is crucial to preserve key surface functional groups and avoid excessive degradation.

SP:Phytotoxicity assessment is mentioned in one of your publications. For our readers concerned about environmental impact, how do you ensure that the treated water, or even the spent biochar itself, is safe for release back into the environment or for other uses like irrigation? What methodologies do you use for such assessments?

RC: Although we have not explicitly conducted research in this, I feel it’s important to discuss the methodologies required to ensure environmental safety. Phytotoxicity assays are commonly conducted using seed germination and root elongation tests with crops such as mung bean and mustard to assess the environmental safety of treated water or spent biochar. Spent biochar is typically analyzed for the stability of adsorbed pollutants using methods like the Toxicity Characteristic LeachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More Procedure (TCLP). Only after confirming that leaching levels are below regulatory limits are spent materials considered safe for reuse as soil amendments or construction fillers. Ensuring environmental safety remains a fundamental priority in these evaluations.

SP:You’ve published numerous papers in leading journals and serve as a reviewer yourself. What, in your opinion, are the most exciting frontiers or unanswered questions in biochar and hydrochar research that you hope to see addressed in the next few years?

RC: One of the most exciting areas in biochar and hydrochar research is finding ways to remove persistent pollutants like PFAS and microplastics, which are hard to get rid of using traditional methods. Researchers are also working on new techniques to watch how these materials break down contaminants in real time, using tools like in situ spectroscopy. Another promising direction is creating hybrid materials by combining biochar with enzymes to improve their cleaning power. There is still a lot we don’t know about how biochar changes over time in the environment, such as how well it continues to capture pollutants, how it gets clogged or worn out, and how its structure changes. Learning more about these aspects is important to make sure biochar works well and stays safe to use in the long run.

SP: Given the complexity of real-world wastewater, which often contains a cocktail of pollutants, how do your engineered biochar and hydrochar systems maintain their high removal efficiencies and selectivity, as you’ve highlighted in your research? Are there specific strategies you employ to mitigate competitive adsorption effects?

RC: We design biochar/hydrochar with tailored surface functionality, introducing heteroatoms that bind selectively to priority contaminants. Moreover, we incorporate multipore systems (micro, meso, and macro pores) to ensure the diffusion of varied molecules. Surface charges are tuned to target ionic species, and real wastewater spiking experiments are run to optimize competitive scenarios. The key is to engineer specificity without sacrificing broad functionality.

SP:Your expertise spans a wide array of high-end instrumentation, from HPLC to XPS. Which instrument do you rely on most to unlock the secrets of biochar and hydrochar’s performance, and why?

RC: If I had to choose one, it would be X-ray Photoelectron Spectroscopy (XPS). It reveals surface elemental composition and bonding states, helping us understand how functional groups are formed, modified, or lost during use. It’s especially useful for validating doping, redox transformations, and postreaction surface chemistry.

SP:Looking ahead, what are your next big goals or research directions in advancing sustainable water treatment technologies using carbonaceous materials? Are there any new contaminants or processes you’re eager to tackle?

RC: The next phase of research will focus on expanding the functionality and real-world applicability of carbonaceous materials in water treatment. One key goal is to develop biochar and hydrochar composites that can act as both adsorbents and catalysts, allowing for the combined removal and degradation of contaminants in a single step. This includes targeting emerging pollutants like endocrine-disrupting chemicals, antibiotics, and pesticide residues, which are increasingly detected in surface and groundwater.

Another important objective is to optimize these materials for use in dynamic flow systems, such as fixed-bed or column reactors, to better mimic industrial or municipal water treatment processes. Current lab studies are mostly batch-based, and translating these results to scalable systems is essential for practical use. Additionally, the research will aim to incorporate machine learning and predictive modeling to design biochar with specific surface properties based on contaminant profiles, thereby speeding up material development. Ultimately, the goal is to bridge the gap between lab-scale innovation and field-scale implementation by focusing on materials that are cost-effective, scalable, and environmentally responsible.

SP:For readers who might be considering implementing biochar solutions in their own communities or businesses, what are the key regulatory or policy considerations that need to be addressed to facilitate the widespread adoption of biochar-based water treatment technologies?

RC: We need clear standards for biochar quality, toxicity limits, and waste classification policies. Additionally, biochar applications must be integrated into national wastewater reuse guidelines, particularly in developing countries. Incentivizing industrial-scale biochar production from agrowaste through subsidies or carbon credits could also drive adoption.

SP:  Looking beyond water treatment, based on your deep understanding of biochar and hydrochar properties, are there any other emerging applications for these materials that you find particularly exciting or promising for the future?

RC: Biochar can be used in many areas beyond water treatment. For example, it’s being explored for energy storage in supercapacitors, and as a material for membranes used in desalination to make seawater drinkable. Biochar also shows promise in improving soil health by supporting helpful microbes. Other interesting uses include capturing and storing carbon, making stronger and more eco-friendly concrete, and even serving as a material for delivering medicines in the body. These examples show that biochar is a very versatile material with many possibilities still being discovered.

SP: Ragavan, with all your incredible work transforming sawdust into powerful water purifiers and catalysts, if biochar and hydrochar could suddenly talk, what do you think would be the first complaint they’d have about their job, and what’s the one thing they’d brag about the most? I expect the funniest scientific answer!! (just to make the whole scene cool and funny)

RC: It’s appreciable that you are asking some funny questions to make the discussion more interesting.

Complaint
‘Why am I always dumped into the dirtiest water?’

Brag
“But hey, I’m the only one who can trap drugs, dyes, and metals all in one go. Even superheroes don’t multitask like me.”

SP: For our readers who are keen to learn more about your innovative work, where can they find more information about your research or connect with you? Do you have a professional website or a research profile you’d like to share?

RC: You can check out my publications on Google Scholar in my name, “Ragavan Chandrasekar.” (Affliation: IIT Guwahati). I’m active on LinkedIn (www.linkedin.com/in/ragavan-chandrasekar-716113152), you can reach out for collaborations and academic discussions. Feel free to reach out via email too (Personal ID: chandrasekarragavan@gmail.com) for research-related queries or possible collaborations.