Efficient clarification of industrial high strength phosphoric acid using microwave-activated carbon-based tire waste residue; Kinetics, isotherm, and thermodynamic studies
This study evaluates the removal of organic matter (OM) from concentrated phosphoric acid as a critical pre-treatment for uranium extraction process. Waste tires were carbonized to produce recovered carbon black particles (AC), which were subsequently activated via microwave treatment (MAC). Both AC and MAC were characterized using FTIR, XRD, Raman spectroscopy, SEM, and BET analysis. OM adsorption experiments were conducted under varying conditions of phosphoric acid concentration, shaking time, temperature, and adsorbent dose. Under optimal conditions (120 minutes, 15 g L -1 sorbent, 43% P 2O5, room temperature), AC achieved a maximum adsorption capacity of 38.46 mg g -1, while MAC reached 47.62 mg g -1. Adsorption kinetics followed pseudo-second-order, with equilibrium data fitting the Langmuir isotherm model. Thermodynamic analysis indicated an endothermic, spontaneous, and feasible adsorption process. This study contributes to improving uranium recovery efficiency from phosphoric acid by addressing organic matter interference. The enhanced OM removal using MAC prepares the phosphoric acid for more effective uranium extraction, potentially increasing yield and purity in subsequent solvent extraction stages, with significant implications for the nuclear fuel cycle and sustainable phosphate resource utilization.
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