Implementation of magnetic bentonite in food industry wastewater treatment for reuse in agricultural irrigation

Abstract

Combining natural materials and pretreatment processes with nanomaterials is an alternative to be evaluated for the increase in efficiency and cost reduction of water treatment processes. This work aimed to study the combination of pretreatment processes and primary treatments with bentonite impregnated with magnetic nanoparticles (Bentonite@MNPs) to reuse wastewater from the food indust|ry. Bentonite@MNPs were obtained by green synthesis using glucose as a reducing/stabilizing agent, and the nanocomposite was characterized by SEM, EDS, FTIR, VSM, and XRD analysis. The synthesized nanocomposite was used to remove nitrates and COD from wastewater from the production of guava bars that had been pretreated with coagulation-flocculation-sedimentation processes. Batch adsorption experiments were conducted, where the influence of several parameters such as contact time, adsorbent amount, and the temperature was studied. According to the results, the wastewater treated with the coagulation-flocculation-sedimentation processes was still outside the standards for agricultural reuse. After applying the treatment with Bentonite@MNPs, a reduction of COD, nitrates, chlorides, and sulfates of 82%, 75.4%, 98.18%, and 70%, respectively, was achieved. The adsorption isotherm data were best explained by the Langmuir model for COD, and Frendluich model for Nitrates and the adsorption capacity of Bentonite@MNPs for COD and Nitrates was 34.84 and 28.11 mg/g when adsorption temperature was 318 K. The results of thermodynamic studies (ΔG°, ΔH°, and ΔS°) showed the spontaneous, endothermic and randomness in the adsorption process. Desorption studies showed excellent regenerative efficiency (up to the 10th cycle) of nanocomposites using 0.01 M NaOH, so this wastewater treatment system for the food industry is promising to implement for the sake of using wastewater as a circular economy component.