End-use application of spent adsorbent from food waste – perspective of the circular economy

Adsorption is a popular pollutant removal method due to its efficacy, competitive cost, ease of use, and compatibility with various wastewater treatment systems. Wastewater adsorption-treatment requires the recovery and environmentally friendly management of spent adsorbents. Water contamination is caused by population growth and industrialization. The prevalence of heavy metals in wastewater is highly subject to human and environmental health risks. Large quantities of adsorbents in wastewater treatment plants (WWTPs) may generate secondary waste, which could be problematic during the life cycle of the adsorbent. When adsorbents are not properly handled after removing the pollutants, they are discharged into the environment and constitute secondary pollution. This review focuses on the application of spent adsorbents in miscellaneous uses and further management through reuse or safe disposal. Scopus, Web of Science, and PubMed were used to conduct a systematic literature review from 2000 to 2024. Terms included “food waste,” “adsorbent recycling,” “used adsorbent,” “recovery,” and “circular economy.” Spent adsorbents can be used in cement and construction composites to improve mechanical properties, photocatalysts for organic pollutant degradation and energy recovery, electrode and sensing materials for forensic and energy uses, and antimicrobial and catalytic systems. This review combines bibliometric data with a critical analysis of reuse options. The study found that encouraging food waste adsorbent reuse and safe recovery can reduce secondary pollution, conserve resources, and promote environmental sustainability.