A study published in Environmental Science and Pollution Research by authors Thalita da Silva Neto, Bianca A. R. Silva, Rennan F. S. Barbosa, Fernanda R. Pinhati, Maria Ismênia S. T. Faria, Derval S. Rosa, and Daniella Regina Mulinari presents a strategy for converting corn husk residue into functional biochar adsorbents. Agricultural waste generation has expanded rapidly, leaving large quantities of corn husks underutilized. At the same time, synthetic dyes such as cationic methylene blue and anionic methyl orange present significant industrial wastewater treatment challenges due to their high solubility and resistance to natural biological degradation.

To address both waste management and water pollution, the researchers investigated two distinct chemical activation routes to tailor the physical and chemical properties of biochar derived from corn husks. One batch of 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 was impregnated with phosphoric acid to yield acid corn biochar, while another was treated with sodium hydroxide to produce alkaline corn biochar. Both materials were subsequently pyrolyzed at 600 degrees Celsius under an argon atmosphere.

Characterization revealed contrasting structural and chemical transformations between the two treatment methods. Acid activation introduced a high density of oxygenated acidic functional groups, such as carboxyl and phosphate esters, while developing uniform mesoporosity. In contrast, alkaline activation resulted in a more highly carbonized, hydrophobic surface with neutral or basic surface groups and hierarchical macro-porosity.

Batch adsorption experiments showed that both biochars were capable of removing both cationic and anionic dyes, though their performance varied. The acid-activated biochar demonstrated superior performance, reaching maximum uptake capacities of 60.2 milligrams per gram for methylene blue and 54.4 milligrams per gram for methyl orange. By comparison, the alkaline-activated biochar achieved capacities of 33.7 milligrams per gram for methylene blue and 40.8 milligrams per gram for methyl orange. Kinetic analysis indicated that the adsorption processes predominantly followed a pseudo-second-order model, pointing toward chemisorption as the primary governing mechanism.

The authors concluded that chemical activation of agricultural corn residue provides a versatile, cost-effective route for manufacturing tailored adsorbents. The findings demonstrate that acid-activated biochar is particularly well-suited for simultaneous cationic and anionic dye removal, offering a viable waste-to-resource approach for industrial effluent remediation.

Source: Neto, T. d. S., Silva, B. A. R., Barbosa, R. F. S., Pinhati, F. R., Faria, M. I. S. T., Rosa, D. S., & Mulinari, D. R. (2026). Valorization of biochars derived from corn straw waste for the adsorption of methylene blue and methyl orange dyes: influence of acid and alkaline activation. Environmental Science and Pollution Research.