Characteristics of Chrome Complexes in Neutralizing Effluent

Abstract

ABSTRACT. In order to explain the reason of chromium released from chrome tanned leather to effluent in neutralizing, the chromium complex composition, structure and property in neutralizing effluent were characterized. Hide powder was tanned by chromium sulfate liquor with 33% basicity (BCS), and then the tanned hide powder was treated by conventional neutralizing to prepare neutralizing effluent (NE). Ion exchange chromatography (IEC) and gel filtration chromatography (GFC) were used to separate NE to study its chromium composition firstly; then ultraviolet-visible absorption spectroscopy (UV) and Fourier Transform Infrared Spectroscopy (FT-IR) were combined to analyze the structure of chrome complexes in NE; at last, chromium from NE was used for tanning and the thermal properties of the tanned hide powder were measured by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The results indicated that NE mainly consisted of anionic-zero valent, monovalent and bivalent chrome complexes and the molecular volume was small also. The Cr(III) complexes in NE were mainly combined with ligands like SO 4 2-and HCOO -through single point coordination. Compared with the control, higher weightlessness rate but lower maximum thermal decomposition temperature (T max ), thermal denaturation temperature (T d ) and enthalpy (ΔΗ) of NE chrome tanned hide powder demonstrated poor tanning ability of the chromium. In short, the characteristics of chromium complexes released from neutralizing process were: anionic-zero valent and low positive charge composition, small molecular volume, mainly combined with ligands through single point coordination and poor tanning ability. The study would provide foundation and reference for developing chromium solidifying methods in neutralizing. KEY WORDS: neutralizing effluent, chromium complex, composition, structure, tanning property CARACTERISTICILE COMPLECŞILOR DE CROM DIN EFLUENTUL DE LA NEUTRALIZAREREZUMAT. Pentru a explica eliberarea cromului din pielea tăbăcită în crom în efluentul de la neutralizare, au fost caracterizate compoziţia, structura şi proprietăţile complecşilor de crom din efluentul de la neutralizare. S-a tăbăcit pulbere de piele cu soluţie de sulfat de crom cu bazicitate de 33% (BCS), apoi pulberea de piele tăbăcită a fost supusă unui proces convenţional de neutralizare pentru a prepara efluentul rezultat în urma acestei operaţiuni (NE). Mai întâi s-au utilizat cromatografia prin schimb ionic (IEC) şi cromatografia prin filtrare cu gel (GFC) pentru a separa NE în vederea studierii compoziţiei sale în crom, apoi s-au combinat spectroscopia de absorbţie în ultraviolet-vizibil (UV) şi spectroscopia în infraroşu cu transformată Fourier (FT-IR) pentru a analiza structura complecşilor de crom din NE; în cele din urmă, cromul din NE a fost utilizat pentru tăbăcire, iar proprietăţile termice ale pulberii de piele tăbăcită au fost măsurate prin analiza termogravimetrică (TG) şi calorimetrie de scanare diferenţială (DSC). Rezultatele au indicat că NE a conţi...

A faster and more effective chrome tanning process assisted by microwave

“…Moreover, there are four peaks for the two samples in the wavenumber range from 900 cm À1 to 1300 cm À1 , indicating that the combination between chromium and sulfate anion in both the samples were double-point coordination. 32 FT-IR results showed that the collagen secondary structure including the triple helix structure was not impacted, and the combination pattern between chromium and the ligands was maintained when microwave was used to promote the chrome tanning process.…”

Influence of microwave on chromium complex composition in tanning liquor

“…Elution conditions were selected as follows: flow velocity of eluent of 2.5 mL/min, followed by using H 2 O, 0.5 mol/L NaClO 4 , 1.0 mol/L NaClO 4 , 2.0 mol/L NaClO 4 , 2.0 mol/L HCl and 2.0 mol/L HCl to elute. UV1900 UV-Vis spectrophotometer was used to detect the absorbance at 420 nm for each 7.5 mL eluent [23,24,27].…”

“…1. According to prior studies, the chromatographic peak I to peak VI represent anionic-zerovalent, monovalent, bivalent, trivalent, tetravalent and pentavalent chromium complexes respectively [23,24,27]. The contents of each composition in WB, MW and control can be calculated based on the area of ion-exchange chromatographic peaks and the results are listed in Table 1.…”

“…The different chromium complex composition should be responsible for the diversity [17][18][19][20]. Ion exchange chromatography (IEC) and gel filtration chromatography (GFC) were widely used to study the composition of chromium tanning liquor [21,22] and they also had been used to clarify chromium complex composition in leather making to provide hint for cleaner process [23,24]. Hitherto, it had been proven that microwave could promote the hydrolysis and olation chromium tanning liquor further due to existence of non-thermal effect [25,26].…”

Chrome Complexes in Rewetting and Neutralizing Effluents and Hints for Recycling Post-Tanning Wet-Process Effluent

“…Elution conditions were selected as follows: flow velocity of eluent, 2.5 ml/min; H 2 O was used to elute. A UV-Vis spectrophotometer was used to detect the absorbance at 420 nm in comparison to SC [20][21].…”