Composition, Property and Structure of Chrome Complexes in Neutralizing Effluent

In order to interpret the reason of chromium complexes release from the chrome tanned leather during the neutralizing process, the hide powder was tanned by chromium sulfate liquor with 33% basicity (BCS), and then the tanned collagen was treated by general neutralizing process to obtain neutralizing effluent. Ion exchange chromatography (IEC) and gel filtration chromatography (GFC) were used to separate neutralizing effluent; Ultraviolet-visible absorption spectroscopy (UV-Vis) and Fourier Transform Infrared Spectroscopy (FT-IR) were combined to analyze the structure of chrome complexes in the neutralizing effluent. The results indicated that the neutralizing effluent mainly consisted of anionic-zero valent, monovalent and bivalent chrome complexes; the molecular weight of chrome complexes in neutralizing effluent was far less than BCS; releasing chromium complexes were mainly combined with ligands through single point coordination and Cr3+ was mainly combined with SO42- and HCOO- by single point coordinate bond. Combined all of the results above, it could deduce that the main constitutes of anionic-zero valent and low electro-positive, smaller molecular, mainly combined with single point coordination are the properties and structural characteristics of the chromium complexes released from chrome tanned leather in neutralizing process.