Banana Peels and Sugarcane Waste Team Up to Pull Ammonium From Water

In a twist that sounds almost too neat to be true, researchers in Taiwan have shown that two of the world’s most abundant agricultural wastes—sugarcane bagasse and banana peels—can be combined into a low-cost water purification material that strips ammonium from contaminated water. The study, published in Discover Chemistry by Hervan Marion Morgan Jr., Tsair-Bor Yen, and Wen-Tien Tsai of National Pingtung University of Science and Technology, offers a striking demonstration that the most effective adsorbents do not always require exotic chemicals or billion-dollar facilities. Sometimes, the answer is sitting in the compost heap.

The environmental problem the team targeted is anything but trivial. Ammonium, the workhorse nitrogen compound of modern agriculture, leaches relentlessly from fertilized fields into rivers, lakes, and coastal waters. Once there, it fuels eutrophication—the runaway growth of algae and seaweed that suffocates aquatic ecosystems. The consequences are particularly visible in regions like the Caribbean, where massive seaweed blooms linked to nutrient enrichment and warming oceans have damaged coastal ecosystems and disrupted local livelihoods. With global sugarcane production topping two billion metric tons annually and banana production adding another 139 million metric tons, the residues from these crops represent both a disposal burden and, as this study shows, an untapped resource.

The core innovation lies in how the banana waste was used. Rather than relying on laboratory-grade reagents and specialized equipment—the standard approach in most biochar modification research—the team created a modifying extract from banana peel powder and banana peel ash. The peel contributes oxygen-rich organic compounds such as hydroxyl, carboxyl, and phenolic groups, while the ash supplies alkali metals, particularly potassium and sodium. The researchers mixed 20 grams of peel powder with 4 grams of ash in either hydrochloric acid or sodium hydroxide solution, stirred the mixture at 80 degrees Celsius for four hours, and filtered out the resulting extract. Direct characterization of the dried extract confirmed its dual nature: Fourier-transform infrared spectroscopy revealed hydroxyl, carboxylate, and carbon-oxygen functional groups, while energy-dispersive X-ray spectroscopy showed the residue was 52.37 percent oxygen by weight, with sodium at 20.36 percent and potassium at 14.31 percent.

The sugarcane bagasse itself was first converted to biochar through pyrolysis in a nitrogen atmosphere. Using a central composite design to balance carbonization quality, yield, and pore development, the team settled on a pyrolysis temperature of 600 degrees Celsius and a residence time of 69 minutes. The resulting pristine biochar, labeled SC-Opt, boasted a respectable BET surface area of 123.62 square meters per gram. The researchers then tried both pre-treatment—soaking raw bagasse in the extract before pyrolysis—and post-treatment—soaking the finished biochar afterward—with acidic and basic versions of the extract, producing four candidate materials.

The winner was SC-Pre-B, the biochar pre-treated with the basic banana peel-ash extract, and its performance profile challenges one of the field’s most intuitive assumptions. Pre-treatment with the basic extract collapsed the biochar’s surface area from 123.62 square meters per gram down to just 1.00 square meter per gram, as salt crystals deposited within micropores and the compromised biomass structure fused during pyrolysis. Yet this seemingly destructive change coincided with a dramatic improvement in ammonium uptake. In screening experiments, the pristine biochar adsorbed a mere 0.7 milligrams of ammonium-nitrogen per gram, while SC-Pre-B achieved roughly 4 milligrams per gram—nearly a sixfold increase. Under optimized isotherm conditions, the material reached an experimental maximum adsorption capacity of 17.11 milligrams per gram. The message is unambiguous: for ammonium capture, surface chemistry trumps physical surface area.

The mechanistic explanation rests on three pillars documented through an impressive battery of analytical techniques. First, zeta potential measurements showed that modification pushed the biochar’s surface charge to as negative as minus 52 millivolts, creating a powerful electrostatic pull on positively charged ammonium ions. Second, X-ray diffraction and electron microscopy confirmed that alkali metals from the ash had been embedded throughout the biochar, with potassium chloride crystallites identified as sylvite. These weakly bound potassium and sodium ions serve as exchangeable sites: elemental analysis before and after adsorption showed potassium and sodium levels dropping as nitrogen content rose, direct evidence that ammonium ions had swapped places with the native cations. Third, infrared spectroscopy revealed shifts in hydroxyl and carboxylate bands after adsorption, indicating hydrogen bonding as a secondary stabilizing interaction.

The adsorption kinetics followed a familiar but instructive pattern. A pseudo-second-order model best described the overall uptake, with rapid initial adsorption during the first six hours as abundant negatively charged and exchangeable sites captured ammonium, followed by slower uptake as the process moved into less accessible regions. Segmented intraparticle diffusion analysis identified three distinct stages with progressively decreasing rate constants, and the non-zero intercepts confirmed that diffusion contributed to—but did not solely control—the process. Notably, the researchers were careful to frame the 24-hour contact time as an operational endpoint rather than proof of complete equilibrium, since the final diffusion stage had not flattened to zero. On the isotherm side, the Langmuir-Freundlich model edged out its competitors with the lowest residual sum of squares, Akaike information criterion, and Bayesian information criterion values, pointing to heterogeneous adsorption sites with varying affinities, though the Langmuir model remained statistically comparable.

The study is refreshingly honest about its limitations. A competing-ion experiment showed that potassium ions, even at molar ratios below that of ammonium, significantly suppressed ammonium uptake—capacity fell from 3.4 to 2.2 milligrams per gram as potassium concentrations rose from 15 to 90 milligrams per liter. This revealed that SC-Pre-B operates through non-specific cation exchange rather than selective ammonium binding, meaning performance in real wastewater, with its cocktail of competing ions, would likely fall short of the synthetic-solution results. Reusability testing over five water-regeneration cycles showed the material retained about 57 percent of its initial capacity, a partial but incomplete recovery that reflects the difficulty of regenerating ion-exchange adsorbents with plain water instead of salt or acid solutions.

What makes this work resonate beyond the laboratory is its accessibility. The modification required only moderate heating, stirring, and basic equipment—no ultrasound baths, no ball mills, no rare-earth dopants. Previous efforts to boost biochar’s ammonium capacity have achieved higher numbers, such as 111.87 milligrams per gram for iron-and-nitrogen-modified walnut shell biochar, but at the cost of reagent intensity and technical complexity that put them out of reach for many of the regions where eutrophication hits hardest. By contrast, SC-Pre-B’s moderate capacity of 17.11 milligrams per gram compares respectably with other modified biochars when differences in experimental conditions are considered, and its entire production chain—from sugarcane juice shop to banana research institute—embodies the circular bioeconomy in miniature.

The road to practical application remains long. The authors themselves emphasize that validation with real wastewater, improved selectivity, optimized regeneration protocols, and careful environmental assessment of the acid and base used in extract preparation are all needed before the technology leaves the bench. There is also tantalizing potential in the spent material: ammonium-laden biochar could conceivably serve as a slow-release soil fertilizer, closing the nutrient loop entirely, though its release behavior would need thorough evaluation. For now, the study stands as an elegant proof of concept that the chemistry of waste can outperform the chemistry of the catalog—turning peel and pulp into a filter that defends the very waters that agriculture has fouled.

Subject of Research: Waste-derived biochar modification for ammonium removal from water

Article Title: Sustainable modification of sugarcane bagasse with a novel banana peel ash extract for enhanced ammonium adsorption

Article References: Morgan, H. M., Jr., Yen, T.-B., & Tsai, W.-T. (2026). Sustainable modification of sugarcane bagasse with a novel banana peel ash extract for enhanced ammonium adsorption. Discover Chemistry, 3(1), Article 451. https://doi.org/10.1007/s44371-026-00912-1

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00912-1

Keywords: biochar, ammonium adsorption, sugarcane bagasse, banana peel ash, water treatment, eutrophication, cation exchange, agricultural waste, circular economy, pyrolysis, zeta potential, adsorption kinetics