Low-cost natural adsorbents have emerged as a promising and sustainable approach for removing metal contaminants from wastewater, addressing both environmental and economic concerns. Derived from readily available agricultural and industrial by-products, these materials offer a viable alternative to conventional, expensive adsorbents like activated carbon. Various types have been explored, including carbon-based materials (biochar), agricultural residues (rice husks, fruit peels), marine algae, clay minerals, and fungal biomass, each with unique adsorption capacities and mechanisms. These materials effectively capture toxic metal ions such as lead, cadmium, and copper through physical and chemical interactions, providing a practical solution, particularly for communities with limited access to advanced water treatment.
The advantages of these adsorbents are numerous. They offer environmental sustainability by reducing reliance on synthetic materials and minimizing hazardous waste. Their cost-effectiveness stems from the abundance and accessibility of source materials, making them suitable for large-scale applications and developing countries. Many exhibit high adsorption capacities, further enhanced by chemical modifications. Their simple processing and application facilitate integration into existing systems. Furthermore, their utilization aligns with resource recovery, transforming waste products into valuable tools for wastewater treatment, promoting circular economy principles and reducing landfill waste.
Despite these advantages, several challenges remain. A key challenge is the complexity of real-world wastewater, which typically contains a mixture of contaminants, unlike single-pollutant laboratory studies. This necessitates adsorbents with broad-spectrum adsorption capabilities. Limited reusability due to limited adsorption-desorption cycles increases operational costs and waste generation, highlighting the need for effective regeneration strategies. Performance is also sensitive to environmental conditions such as pH, temperature, and pressure, requiring precise control. Finally, the mechanical instability of some biological adsorbents poses challenges during separation and regeneration, although immobilization techniques offer potential solutions but with added complexity and cost.
Continued research and development are crucial to fully realize the potential of these adsorbents. Future efforts should focus on enhancing adsorption efficiency and selectivity, improving operational stability under diverse conditions, developing cost-effective regeneration methods, and investigating the complex interactions of multiple contaminants. By addressing these issues, these natural materials can play a vital role in advancing sustainable and effective wastewater treatment, contributing to a cleaner environment.