For the first time, a simple synthesis of an ionically cross-linked tree gum-based sponge with structural stability was investigated for effective cationic dye adsorption. Hierarchical three-dimensional structures were formed between gum kondagogu (K) and sodium alginate (S) primarily through hydrogen bonding, and enhanced further by Ca²⁺ ionic crosslinking. Fourier transform infrared spectroscopy, TGA, SEM, and micro-CT were used to characterize the sponge. The adsorption capacity of the sponge for the cationic dye, methylene blue (MB), was studied as a function of pH, dosage, reaction time, and initial dye concentrations. The MB adsorption of the sponge in the present work (1250 mg g⁻¹) shows a higher adsorption capacity than many other natural sponges. The maximum adsorption was recorded at pH 9, and recyclability without significant loss of efficiency for five adsorption cycles was also obtained. Furthermore, pseudo-second order kinetics and the Langmuir adsorption isotherm fit the experimental results well. This biodegradable adsorbent is a promising material for cost-effective wastewater treatment via waste-to-resource conversion.