High ash content in algal biomass limits its suitability for biofuel production by reducing combustion efficiency and increasing fouling. This study presents a green deashing strategy using nitrilotriacetic acid (NTA) and deionized (DI) water to purify Scenedesmus algae, which was selected for its high ash removal potential. The optimized sequential treatment (DI, NTA chelation, and DI+NTA treatment at 90–130 °C) achieved up to 83.07% ash removal, reducing ash content from 15.2% to 3.8%. Elevated temperatures enhanced the removal of calcium, magnesium, and potassium, while heavy metals like lead and copper were reduced below detection limits. CHN analysis confirmed minimal loss of organic content, preserving biochemical integrity. Unlike traditional acid leaching, this method is eco-friendly after three cycles. The approach offers a scalable, sustainable solution to improve algal biomass quality for thermochemical conversion and supports circular bioeconomy goals.

This study investigated a green chelation strategy for deashing algal biomass using nitrilotriacetic acid (NTA) and deionized water (DI) to enhance its suitability for biofuel and bioproduct applications. Solid-state algal turf scrubber (SS ATS), green algal turf scrubber (ATS), and Scenedesmus were analyzed, with Scenedesmus selected for detailed evaluation due to its high ash removal efficiency. The objective was to optimize a purification process that minimizes ash and heavy metal content while preserving biochemical integrity. Algal biomass underwent sequential washing with DI, NTA, and NTA+DI under varying temperatures (90-130 °C). Analytical techniques including Fourier Transform Infrared (FTIR) spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and CHN (carbon, hydrogen, nitrogen) elemental analysis were employed to assess changes in ash content, metal ion concentration, elemental composition, and biochemical properties. The NTA+DI treatment was the most effective, lowering the ash content in Scenedesmus from 15.2% to 3.8% and decreasing lead (Pb) and copper (Cu) levels below detectable limits. Ash removal was greatly aided by temperature reaching a high efficiency of 83.07% at 130 °C owing to enhanced calcium, magnesium, and potassium solubilization and chelation. Successive NTA recycling led to a decline in efficiency by the third cycle, indicating chelating agent saturation. Despite ash reduction, the ultimate analysis showed minimal changes in CHN composition (C: 45.2%, H: 6.0%, and N: 7.1%), ensuring the retention of organic matter. These findings established NTA+DI treatment as an effective and sustainable method for deashing algal biomass while maintaining its biochemical integrity. This optimized process enhances the feasibility of Scenedesmus-derived biofuels improving combustion efficiency and reducing inorganic fouling in biorefineries and thermochemical conversion systems.