Jatropha curcas L. as a member of Euphorbiaceae family had many copious applications due to its richness content of oil, cellulose, hemicellulose, and lignin. Therefore, this work was directed to increase the value of the seedcakes of Jatropha curcas by their applications in bioethanol production and removal of methylene blue dye (MB) as well as hexavalent chromium Cr (VI) from contaminated wastewater. The seedcakes sources were collected from different irrigation treatments: tap water (1), sewage water (2), sewage water and sludge (3), sewage water and sludge sprayed with tap water, 100, 200, 300, and 400 ppm of chlorocholine chloride (cycocel or abbreviated as CCC), (4), (5), (6), (7), and (8), respectively. Results showed that sewage water only (2) and the combination between sewage water and sludge irrigation (3) produced the highest ethanol quantity (4.59 & 5.15 ml/l, respectively) after the fermentation of the hydrolysates by Candida tropicalis Y-26. In respect to CCC spraying, the maximum ethanol concentration (5.57 ml/l) was achieved from Jatropha curcas seedcake irrigated with CCC at a concentration of (300 ppm). In the other application, a preliminary screening experiment was demonstrated for the different forms of Jatropha curcas seedcake and results revealed that the Jatropha curcas seedcake irrigated with sewage water only (2) achieved the highest removal efficiencies of 78.8% and 41% for MB and Cr (VI), respectively. After that, the optimization process stated the optimum parameters; Jatropha curcas seedcake dose of 15 and 5 g/l, conc. 50 ppm, pH 7 and 5, and contact time 240 & 120 min were the optimum factors that achieved high (methylene blue (MB)) and hexavalent chromium [Cr (VI)] removal efficiencies, respectively. Langmuir isotherm and the pseudo-first-order model were stated as selected models that explain the adsorption mechanism of MB and Cr by Jatropha curcas seedcake.
