Insights into efficient removal of cationic and anionic dyes by olive pomace adsorbent

Olive pomace (OP) is a widely used agricultural by-product with the potential to promote a circular low-carbon bioeconomy. In this work, an environmentally friendly and low-cost olive pomace adsorbent (OPA) was obtained from olive pomace by drying, crushing, sieving and sterilizing, and confirmed to remove anionic and cationic dyes from wastewater. The present study investigated the impact of adsorbent dosage, dye concentration, contact time, temperature, and pH on the adsorption mechanism, providing a more comprehensive understanding of the adsorption mechanism. The adsorption isotherm and kinetic studies revealed that the adsorption behavior of all 12 dyes followed the Langmuir isotherm model. Among them, the adsorption kinetics of 8 dyes were well described by the pseudo-second-order model, while the remaining 4 dyes fitted better with the pseudo-first-order model. The presence of electrostatic interactions and pore filling in the adsorption process contributed to the excellent adsorption performance of OPA for the 12 dyes. OPA also maintained a high removal rate for dyes after five cycles of regeneration. In addition, the water quality evaluation results show that the dye wastewater quality after OPA adsorption is equivalent to that of drinking water. These results highlight the potential of olive pomace as an eco-friendly and efficient adsorbent for the removal of cationic/anionic dyes from water, contributing to sustainable waste management and environmental remediation.