A study was made on the feasibility of low mordant quantity and minimum chrome residues in dyehouse effluent generated by rare earth salts used with chrome dyes for dyeing wool fabrics. The results showed that the addition of rare earth salts reduced the quantity of mordant used and decreased chrome residues in dyehouse effluent. Among the rare earth salts lanthanum sulfate showed superior effect, and yielded higher color strength and minimum chrome residues at 0.3% o.w.f. Furthermore, a ratio of 6:4 or 4:6 of the rare earth salts and mordant was found to be optimum for dyeing; and lanthanum sulfate and eerie sulfate at a ratio 8:2 showed better effect. Among the dyes used, Blue 1 and Red 94 showed fast dyeing effect, followed by Black 11 and Yellow 25. The washing fastness of woolen fabrics were in the range of grades 3-5, while abrasion fastness ranged in grade 4. Addition of rare earth salts was found to lower the quantity of mordant required, saved energy, reduced pollution, and minimized waste.
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