Development of Xanthan Gum Hydrogels Cross-Linked with Olive Mill Wastewater: A Sustainable Approach to Reusing Olive Oil Residues

Abstract

To achieve sustainable agriculture, it is essential to develop and adopt innovative technologies that take advantage of alternative raw materials and provide effective solutions for industrial waste management. This study focuses on the development of xanthan gum (XG) hydrogels cross-linked with olive oil mill effluent (OMW), a byproduct of the olive oil industry, and explores their application as an innovative strategy for water retention and soil conditioning. Biobased hydrogels are superabsorbent polymers capable of retaining large amounts of water, improving soil hydration, and reducing water stress in crops. The synthesized hydrogels were extensively evaluated through chemical characterization, swelling capacity tests, water retention performance, and thermogravimetric and morphological analyses to elucidate their structural and cross-linking properties. The results showed that the use of OMW as a cross-linking agent allowed the formation of hydrogels with exceptional water absorption capacities, ranging from 6000% to 14,000% (wt %). The analyses confirmed the successful incorporation of OMW into the polymer matrix, highlighting the interactions between the carboxyl and hydroxyl groups characteristic of the material. Furthermore, all hydrogels demonstrated the ability to retain water for up to 7 days, presented biodegradability, and did not exhibit phytotoxicity, reinforcing their suitability for agricultural applications. The OMW/XG hydrogel stands out as an economically viable and environmentally sustainable solution, offering significant potential to improve water management in agriculture. In addition to its water retention capacity, this hydrogel paves the way for the incorporation of fertilizers, creating multifunctional materials with broader applications in agriculture and horticulture. Overall, this work presents an innovative and practical approach to valorizing olive oil mill effluent as a cross-linking agent, contributing to sustainable agricultural practices and promoting the circular economy within the olive oil industry.