Parametric Optimization of Organic Waste Removal Using Agro-Food Carbon–Zeolite Adsorbents

The production of carbonaceous materials from agro-food byproducts, i.e., olive stone and molasses alone or in combination with aluminosilicate minerals, i.e., zeolite, was investigated. Two different dyes, i.e., methylene blue (MB) and C-phycocyanin (C-PhC) contained in Spirulina extract, were used for the examination of the adsorptive properties of the materials. The combination of the Brunauer–Emmett–Teller surface area, X-ray diffraction, and X-ray photoelectron spectroscopy provides a comprehensive profile of composite sorbents. Several key factors, including initial dye concentration, pH, contact time, temperature, and sorbent, were investigated. All the produced adsorbents have shown a highly disordered carbon structure with specific surface areas between 16 and 1211 m2/g. The elemental composition analysis revealed the presence of C-C, C-H, C-O, C=O, O-C=O, and (CO3)2− bonds during high-resolution C1s and O1s deconvolution and detected the elements Al, Si, Na, Ca, K, Na, and S, confirming the aluminosilicate framework of the zeolitic structure of the materials. The examined conditions showed the best MB and C-PhC adsorption results at pH 8, temperatures of 50 °C and 40 °C, respectively, an initial concentration of 0.5 mg/L for MB and 32 mg/L for Spirulina extract (SE), and a sorbent dosage of 2.0 g/L C/MB or SE solution. The adsorbents produced were applied to the removal of C-PhC from industrial waste. To conclude, this research underscores the viability and high efficiency of repurposing agricultural waste into carbonaceous composite sorbents to eliminate dyes from wastewater.