Iron-enriched coal and volcanic rock waste powder composite with enhanced microwave absorption capacity for the degradation of 2,4-D and atrazine pesticides in single and binary systems

Abstract

A novel catalyst was synthesized employing coal and volcanic rock waste (VRW) residues enriched with iron nanoparticles, and its efficiency was investigated upon the degradation of (2,4-dichlorophenoxy)acetic acid (2,4-D) and atrazine (ATZ) pesticides. The composite was synthesized by a facile and effective chemical precipitation technique and extensively characterized by XRD, FTIR, XRF, ICP-OES, ICP-MS, and SEM-EDS. The effects of pH, catalyst dosage, and initial pollutant concentration were investigated in single and binary systems irradiated with microwave (MW) under atmospheric pressure. The optimal reaction conditions were obtained at pH 3 and 5 for 2,4-D and ATZ in single systems and pH 3 in binary systems, respectively, with 20 mg L−1 of initial pollutant concentration and 0.1 g L−1 of CVRWMag (coal, VRW, and nano-Fe3O4) catalyst. The kinetic data fitted better to the pseudo-first-order model (R2 > 0.965). In addition, the phytotoxicity was investigated with Lactuca sativa seeds, and the root elongation and the seed germination rate were enhanced as the MW irradiation time increased. The complete degradation of both compounds was reached within 30 min, with outstanding mineralization efficiency. The degradation efficiency was attributed to hydroxyl radical (OH) formation and electrostatic surface interaction, enhanced by hot spot formation. Therefore, the CVRWMag is a promising MW absorbing catalyst for the removal and degradation of pesticides without the need for H2O2 or any radical enhancing agent addition.