Phosphate removal in a pilot filter system using Sacha inchi cuticle and eggshells

The presence of phosphates in wastewater is a growing concern worldwide, which is why there is currently interest in finding alternatives to remove them and avoid problems such as water eutrophication. Another important trend is the development of processes for utilizing agro-industrial waste to add value to production chains. In this sense, this work studied the removal of phosphates from water using an adsorbent composed of sacha inchi cuticle and eggshell in a 1:10 ratio, pyrolyzed at 400°C for 20 min. For this, a filtration system was constructed using 10 cm diameter PVC pipes and employing 155.56 g of the adsorbent, which corresponded to a filtering medium volume of 1.3x10^-3 m³. With these design parameters, a working flow rate of 0.020 m³/h and a filtration velocity of 2.52 m³/m²*h were established, which would correspond to a filter with an average velocity rate. To test the system, 8L of a solution at a concentration of 133 mg/L of PO₄^-3 was prepared. This solution was pumped through the filter using a submersible pump of 25 W, taking samples while recovering 1, 1.5, and 5 L of filtrate, respectively. Subsequently, through spectrophotometric analysis, the removal of phosphates was quantified in duplicate. As a result, a PO₄^-3 removal percentage of 35.58 ± 1.57% was obtained. It is relevant to note that the filtration time required to recover 5 liters of filtrate was slightly more than 12 min. In conclusion, although the removal percentage is lower than that reported by other authors using similar materials as adsorbents, the difference is likely due to the conditions associated with the preparation of the adsorbent. Other conditions could be assessed to improve the removal percentage, contributing to the understanding of these residues and their valorization in the development of sustainable processes.