Ultrasound-Assisted Synthesis of MXene-Grafted Coconut Husk Activated Carbon for Enhanced Adsorption of Carbamazepine: Batch Study and Optimization

Water is constantly being tested by a new kind of pollution: the invisible residue of modern medicine. Every day, people take pills to manage conditions like epilepsy and mood disorders, and when these drugs leave the body, they often end up in the water supply. Traditional water treatment plants are not designed to catch these specific chemical traces. The molecules are stable, meaning they do not break down easily in the environment, and they can accumulate in rivers and lakes, posing risks to fish and other wildlife. Scientists have long searched for a way to pull these stubborn pharmaceuticals out of the water using materials that are both effective and affordable. The challenge lies in finding a substance that can grab onto these tiny drug molecules and hold them tight, without costing a fortune or requiring complex machinery to operate.

In a recent study, researchers from Jadavpur University in India tackled this problem by combining two very different materials into a single, powerful tool. They took coconut husks, a common agricultural waste product, and turned them into activated carbon, a highly porous material known for its ability to trap impurities. To this, they added a layer of MXene, a type of synthetic nanomaterial made from titanium and carbon that is only a few atoms thick. The goal was to see if this hybrid material could act as a super-sponge for carbamazepine, a widely used antiepileptic drug that is notoriously difficult to remove from water. The team did not just mix the two; they used sound waves and heat to bond the MXene sheets directly onto the surface of the coconut carbon, creating a new nanocomposite designed to maximize the surface area available for trapping the drug.

The researchers began by building their material from scratch. They collected coconut husks from a local shop, cleaned them, and ground them into a fine powder. This powder was heated in a special oven without oxygen to turn it into charcoal, which was then treated with chemicals to open up its pores, creating the activated carbon. Separately, they synthesized the MXene nanosheets from a mineral called MAX phase. The final step involved mixing the two components together in a liquid bath and using ultrasonic waves to shake them apart and spread them evenly, followed by a heating process to fuse them together. The result was a dark, porous powder where the ultra-thin MXene sheets were grafted onto the rough, sponge-like coconut carbon.

To test how well this new material worked, the team placed it into jars of water containing the drug carbamazepine. They varied the conditions to see what worked best, changing the amount of powder used, the temperature of the water, how fast the jars were shaken, and the acidity of the solution. They found that the material was remarkably effective. In the best conditions, the nanocomposite removed nearly all of the drug from the water. Specifically, when they optimized the process, they achieved a removal rate of over 99 percent. The material was also capable of holding a large amount of the drug; in one test, a single gram of the material trapped more than 427 milligrams of carbamazepine. This capacity was significantly higher than what the coconut carbon alone or the MXene alone could achieve, proving that combining the two created a material greater than the sum of its parts.

The study also looked at how the material behaved under different conditions. The researchers discovered that the adsorption process, which is the act of the drug sticking to the surface, worked better at higher temperatures. This suggests that the process absorbs heat, making it more efficient in warmer water. They also found that the speed at which the water was stirred mattered; stirring too slowly meant the drug molecules did not reach the material quickly enough, but stirring too fast actually knocked the drug off the surface, reducing efficiency. The ideal speed was found to be a moderate pace that kept the water moving without being violent. The material worked well across a wide range of pH levels, meaning it could be used in water that was slightly acidic or slightly basic, which is a practical advantage for real-world wastewater treatment.

To understand exactly how the drug stuck to the material, the team examined the surface using powerful microscopes and other analytical tools. They saw that the surface was rough and full of tiny holes, which provided plenty of space for the drug molecules to settle. The chemical analysis showed that the material was covered in various functional groups, such as oxygen and hydroxyl groups, which acted like tiny hooks to grab the drug molecules. The drug molecules likely attached through a combination of forces: they were attracted to the carbon structure through electrical interactions, formed hydrogen bonds with the surface groups, and were physically trapped inside the tiny pores of the coconut carbon. The study ruled out the idea that simple electrical attraction was the only factor, noting that the drug molecule is mostly neutral in water, so the physical trapping and chemical bonding played the dominant roles.

A critical part of any new water treatment material is whether it can be reused. The researchers tested this by washing the material with acid and base solutions to strip off the trapped drug, then using it again. They repeated this cycle seven times. While the material did lose some of its effectiveness over time, dropping from nearly 100 percent removal to about 51 percent by the seventh cycle, it still retained a significant portion of its ability to clean the water. This suggests that the material is durable enough to be used multiple times, which is essential for making the process economically viable. The slight loss in performance was likely due to the gradual breakdown of the material's structure during the chemical washing process, but the fact that it held up at all is a promising sign.

The researchers concluded that this new composite material offers a practical and efficient solution for removing pharmaceuticals from water. By turning a waste product like coconut husks into a high-tech adsorbent and reinforcing it with MXene, they created a material that is both sustainable and highly effective. The study demonstrated that the process is spontaneous, meaning it happens naturally without needing extra energy to drive it, and that it works well under standard conditions. While the material is not yet a permanent fix for all water pollution, it represents a significant step forward in developing affordable, high-capacity tools to clean our water supplies of dangerous drug residues. The work highlights how combining simple, natural materials with advanced nanotechnology can solve complex environmental problems.