This study investigated the use of oxalic acid as an eco-friendly compound for extracting ulvan from Ulva linza biomass. The concentration of oxalic acid, temperature, and period of extraction were optimized using Box-Behnken design in response of ulvan yield, molecular weight (MW), sulphate content, uronic acid content, purity ratio (total sugars/total phenolics and proteins), and Fe(III) chelation properties. Under the optimized conditions (1.7 % w/v oxalic acid, 64 °C, and 2.63 h), ulvan yield, MW, sulphate content, uronic acid content, and purity ratio were 29.90 % (w/w), 32.22 kDa, 11.01 % (w/w), 8.12 % (w/w), and 12.84, respectively. The optimized ulvan exhibited good Fe(III) chelation of 18.58 % (w/w). The synthesized Fe-ulvan complex released approximately 73 % of the chelated Fe(III) under in vitro simulated gastro-intestinal conditions. Furthermore, both ulvan and Fe-ulvan complex exhibited potent antioxidant properties. FT-IR analysis confirmed the fundamental role played by hydroxyl, carboxyl and sulphate groups in the coordination of Fe(III). Furthermore, MW, MW/sulphate ratio, and MW/uronic acid ratio should be low to enhance the Fe(III) chelation properties of ulvan. The results of the present study shed light on the use of oxalic acid as a simple and environmentally-benign treatment for ulvan extraction, especially for the recovery of low MW ulvan with high yield and good Fe(III)-binding properties.