Bio-desalination of seawater using cyanobacteria–plant biomass hybrid system: experimental investigations and sustainable prospects

Abstract Freshwater scarcity and the rising global demand for sustainable desalination have intensified the search for low-cost, eco-friendly technologies. This study presents a novel bio-desalination approach using the dried biomass of the cyanobacterium Nostoc spongiaeforme FACHB-130 and hydrothermally pretreated powder of Mentha piperita L., applied individually and in combination for the treatment of raw Red Sea water. Comprehensive biomass characterization using FTIR, SEM, and EDX confirmed the presence of abundant functional groups, high surface porosity, and active adsorption sites responsible for ion binding. The effects of biomass dose, contact time, and repeated batch runs were investigated, supported by adsorption kinetics and isotherm modeling. The hybrid cyanobacteria–plant system exhibited superior desalination performance, achieving cumulative reductions of 20.6% (EC), 24.7% (TDS), and 34.5% (Cl⁻). Adsorption data followed pseudo-first-order with TDS removal approach and pseudo-second-order kinetics for Cl − ions and fitted well with the Freundlich isotherm, indicating heterogeneous multilayer biosorption. The enhanced performance was attributed to the synergistic interaction between the biopolymeric matrix of N. spongiaeforme and the porous, chemically active surface of M. piperita . Overall, this study introduces a sustainable and energy-efficient bio-desalination strategy that can serve as a pretreatment step for seawater reverse osmosis (SWRO), potentially reducing membrane fouling and operational costs. The results obtained indicated that these biomasses provide an eco-friendly alternative sorbent biomaterial for salinity removal from real seawater.