BACKGROUND Collagen fibers from tannery solid wastes were treated with aqueous solutions of inorganic salts. The effect of the inorganic salts on the dissolution of collagen fibers and degradation of collagen were investigated. Tests of reduced viscosity and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) were applied to evaluate the degree of degradation during the dissolution process. The specific ionic effects of the Hofmeister series on the dissolution of collagen fibers in salt aqueous solutions were demonstrated. RESULTS According to all the results, the dissolution abilities of inorganic salts were in the order of Br- > Cl- > SCN- > CH3COO- > H2PO4- > CO32- as well as Na+ > Mg2+ > Ca2+ > NH4+ > K+ > Li+. The results indicated that NaBr aqueous solution could have potential ability as a solvent to dissolve collagen fibers without excessive degradation of collagen. CONCLUSIONS NaBr aqueous solution could have potential ability as a solvent to dissolve collagen fibers without excessive degradation of collagen. By analyzing the results of the reduced viscosity tests, SDS-PAGE and amino analysis, proper dissolution conditions were evaluated with the conditions of NaBr aqueous solution concentration of 1 mol L-1, contacting time of 4 h and temperature of 60 degrees C. From amino analysis and in situ optical microscopy observation, a possible process of collagen fiber dissolution in NaBr solution was demonstrated. This work provides a method for treating and recycling tannery solid wastes with some information for the investigation of collagen-based materials. (c) 2019 Society of Chemical Industry