Title : Circular valorization of industrial and agri food by products into adsorbents for industrial effluent treatment
Abstract:
Textile effluents, characterized by high dye concentrations, organic load, suspended solids, and variable pH, pose significant environmental and regulatory challenges due to their complex composition and recalcitrant pollutants. The development of efficient, sustainable, and operational treatment materials is therefore essential. In this context, the present study investigates the performance of a composite geomaterial, designated GEO-85, developed from industrial and agricultural by-products within a circular economy framework.
GEO-85 is composed of 85% kaolin industrial by-product, 10% activated carbon derived from jujube stones, and 5% fine gypsum acting as a mineral binder. The kaolin was purified and converted into its homoionic sodium form to enhance cation exchange capacity, while the activated carbon was produced by chemical activation of jujube stones using phosphoric acid. The formulation was optimized to combine adsorption efficiency with mechanical stability, enabling direct application to real industrial effluents.
Comprehensive characterization of GEO-85 was performed using FTIR, SEM, and XRD analyses to assess functional groups, morphology, and mineralogical structure. Key physicochemical properties, including moisture content, Cation Exchange Capacity (CEC), pHpzc, methylene blue index, and specific surface area, were also determined to evaluate adsorption potential.
The material was tested on two real textile effluents (mustard and purple) collected from industrial discharge. Batch experiments were conducted under ambient conditions to evaluate the influence of contact time (5–180 min) and adsorbent dosage (0.1–6 g/L) on decolorization efficiency. Optimal conditions were achieved at a contact time of 120 minutes and a GEO-85 dose of 5 g/L. Under these conditions, removal efficiencies reached 83.04% for the mustard effluent and 79.93% for the purple effluent. In addition to color removal, significant reductions were observed in turbidity, suspended solids, Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD), with COD reduction reaching up to 73.83%. The treated effluents complied with Algerian discharge standards.
The results demonstrate that the synergistic integration of mineral (kaolin, gypsum) and carbonaceous (activated carbon) components within a single matrix provides both structural stability and enhanced adsorption performance. Beyond decolorization, the material effectively reduces the global organic load of complex industrial effluents. Overall, GEO-85 represents a sustainable, low-cost, and operationally viable adsorbent for industrial wastewater treatment. By valorizing kaolin industrial by-products and agricultural residues, this approach contributes to resource recovery strategies and supports circular economy principles while addressing pressing environmental challenges associated with textile wastewater discharge.
