ROW Controller providing OJT described near terrain separation event when assisting a general aviation aircraft with icing concerns; radio reception problems adding to the event scenario.

Narrative

Aircraft X came onto frequency at 8;000 ft MSL asking for lower due to icing. I immediately considered this an emergency situation. My trainee descended him to 7;500 reference a 7;300 ft isolated tower MVA directly in front of the aircraft. I told the trainee to descend him to 7;300 and ask him if he'd like a vector around the MVA so he could descend to 6;000. He replied 'OK; Descending to 6;000'. The trainee immediately APREQED control for turns from the adjoining sector (MAF-Lo). The trainee told him to turn right to 300 degrees; which was not enough to miss the 7;300 MVA ring. I took the frequency and turned the aircraft to 360 degrees. The pilot's read back was never received. The aircraft continued on a 360 heading for approx 17 NM; descending to and level at 6;000. The aircraft was headed for another isolated tower MVA of 7;100. Multiple attempts to re-establish communications were made with main; standby; and emergency transmitters; on both normal and emergency frequencies. The aircraft finally re-established communications and took a vector heading 270 to avoid the tower. Bearing and distance to the tower (12 o'clock and 5 NM) were both issued to the aircraft multiple times. After re-establishing communications with the aircraft; the aircraft was vectored for an ILS approach into ROW without further incident. Recommendation; as a pilot; my priority was to descend the aircraft for icing. Though the MVA in that area is 6;000; reception is patchy depending on the aircraft involved. Having never worked an aircraft at that MVA (all traffic comes over at or above 8;000 due to the 7;300 MVA ring); I was unaware that reception could be lost. With this information; I could have made better vectoring decisions. Perhaps a map can be created graphically displaying areas of concern for reception coverage. This map would have been very effective in preventing this and similar situations.