I have heard from Rav Daniel Glatstein shlita (Shiur: Parshas Emor: The Mystical Dimensions of Shabbos - When They Arrive and How to Hold On To Them), that there is a concept that the six perakim of Tehillim (95-99 and 29), we recite on Kabbalos HaShabbos, are to clean ourselves from the "weekday-klipos", the impurity we got during the week. We don't want that on Shabbos, so these chapters are to cleanse ourselves from that.
These psalms purify and refine our souls in preparation for the holy Shabbos. We recite them to remove the klipos accumulated during the weekdays and to sanctify ourselves in the light of Shabbos.
Does anyone know where this section of Masok Midvash can be found (is it online? -EDIT: FOUND, THANKS TO YOREINU)
and why especially these six chapters are to "cleanse our souls for Shabbos"? What is so special about them? Please cite sources.