Optimizing Nitrate and Nitrite Recovery from Aquaculture Wastewater Using Coffee Ground Biosorbent: Adsorption Mechanisms and Its Potential as Soil Conditioner

Aquaculture wastewater (AW) is contaminated with nitrate (NO₃⁻) and nitrite (NO₂⁻), which can cause eutrophication if discharged without treatment. This study explores using coffee grounds biosorbent (CGB) to recover NO₃⁻ and NO₂⁻ ions from AW and reutilize the spent sorbent as a soil conditioner. The process study, adsorption isotherms and kinetics of the adsorption of NO₃⁻ and NO₂⁻ were deduced using several parameters and models. Spent sorbents were also compared with the commercial potting soil based on Okra plant growth metrics. The highest recovery efficiency for NO₃⁻ and NO₂⁻ was 98.6% and 95.0%, respectively, using 5 g/L of CGB with a 2-h contact time at pH 11. Adsorption followed the Freundlich isotherm and pseudo-first-order model, indicating multilayer adsorption on a heterogeneous surface. Optimal Okra growth was observed with 10% spent CGB (SCGB). This study highlights the potential of waste biosorbents for nutrient recovery and subsequent use as soil conditioners.