Response surface optimization for cadmium biosorption onto the pre-treated biomass of red algae Digenia simplex as a sustainable indigenous biosorbent 1Department of Biology, College of Science, Sultan Qaboos University, Muscat, Oman 2Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia 3Department of Biology, Faculty of Science, Umm Al-Qura University, Makkah, Saudi Arabia 4Faculty of Science, Biology Department, Taif University, Taif,...