Eco-friendly polycaprolactone-bound diatomite filter for the removal of metal ions and micro/nanoplastics from water

Over the last few decades, pollution levels in aquatic environments due to heavy metal ions and micro/nanoplastics have increased owing to industrial development, causing adverse effects on microorganisms. Adsorbent-based filtration is a well-developed technique for removing contaminants from aquatic environments. However, this technique should be improved from the perspectives of eco-friendliness and cost-effectiveness, as commercial adsorbents require energy-intensive synthesis and post-processing with chelating agents. In this study, an eco-friendly filtration system was developed. This system employs biodegradable, natural materials, such as diatomite to remove metal ions and micro/nanoplastics and polycaprolactone (PCL) to make the free-form shapes. The filter removes metal ions via adsorption and micro/nanoplastics via physical size filtration and adsorption. This PCL-bound diatomite filter was fabricated from a mixture of acetone, PCL, and diatomite, varying its size, thickness, shape, and stacking number for a particular objective and usage. The adsorption capacity, kinetics, and permeation flux of the membrane were measured, and the stacking number of the membranes were optimized to maximize the removal efficiency of the target contaminants. This filter is completely biodegradable, as indicated by the degradation of the PCL binder within 60 days in water, without any treatment. The degradable, eco-friendly PCL-bound diatomite filter is a low-cost and sustainable component that can be utilized in various applications, especially potable drinking water production from river in developing country and filtering the micro/nanoplastics from the commercially bottled drinking water in daily life.