This article introduces an efficient, low cost, and clean (zero pollution) zone melting phosphorus purification technique. We have successfully removed arsenic from solid phosphorus by melting a narrow region and making the resulting liquid zone travel slowly through a relatively long ingot of phosphorus. This technique can reduce arsenic concentration in solid phosphorus from 100 ppm to 10 ppm in a specific condition. Purified solid phosphorus can be used to produce 85% phosphoric acid with arsenic concentration of 2.8 ppm as an additive in the food industry (lower than both the Food and Drug Administration standard (FDA) and the Food Chemicals Codex standard (FCC) of 3 ppm for food grade phosphoric). We applied the phase-field model to establish a system of PDEs and numerically obtained a continuous melting zone moving along with the heater. (C) 2012 Elsevier B.V. All rights reserved.