March 2018 Abstracts

Effect of Leather Chemicals on Cr(III) Removal from Post Tanning Wastewater

by Yuling Tang, Jianfei Zhou, Yunhang Zeng, Wenhua Zhang and Bi Shi

The effect of typical leather chemicals on removal of Cr(III) from tannery post tanning wastewater by PAC coagulation was investigated. It was found that all the leather chemicals investigated could form complexes with Cr(III) through their anionic hydrophilic groups. The determinations of fluorescence quenching titration indicated that the Cr(III)-complexing ability of these anionic hydrophilic groups was in the sequence of phenolic hydroxyl of vegetable tannins and syntans > carboxyl of acrylic resins > sulfonic acid group of fatliquors and dyes. The complexes formed had higher hydrophobicity because a part of anionic hydrophilic groups of leather chemicals were blocked. The Cr(III) complexes with vegetable tannins, syntans and dyes were in the form of hydrophobic colloid or particle due to both the blocking effect of hydrophilic groups and the strong hydrophobicity of benzene ring, which favored the removal of Cr(III) from post tanning wastewater by coagulation (removal extent 82%-99%). But the Cr(III) complexes with acrylic resins existed as water-soluble pieces, probably because a part of free carboxyl group still kept on the polymer chain at reaction equilibrium, and acrylic resins had no structure/group with hydrophobicity as strong as benzene ring. As a result, Cr(III) was difficult to be removed from wastewater when acrylic resins existed (removal extent <60%). That is, the formation of Cr(III)-acrylic resin complexes is the major obstacle in removing Cr(III) effectively from post tanning wastewater.

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Five Tanning-dyeing Processes Based on Triphenodioxazine (TPDO)

by Tianyu Liang, Jun Liu and Keyi Ding

Triphenodioxazine (TPDO) is a high-performance chromophore. Based on TPDO, five simultaneous or combined tanning-dyeing processes were undertaken with pickled sheep pelt. Process 1 utilized a simultaneous tanning-dyeing material named TPDO-GT, a reactive dyestuff with aldehyde reactive groups which was prepared by grafting TPDO to the backbone of a glutaraldehyde-like compound (GT). The other four processes were combinations of TPDO with gallic acid (GA) and Al (III), Fe (III) salts, through treating the pelt using a different adding order. The adding order of Process 2 was to treat the pelt with Al (III) salt first and then the mixture of (TPDO+GA); that of Process 3 was to add the mixture of (TPDO+GA) first and then the Al (III) salt; that of Process 4 was to add Fe (III) salt first and then the mixture of (TPDO+GA); that of Process 5 was to add the mixture of (TPDO+GA) first and then Fe (III) salt. Tanning-dyeing effects of the five processes were compared, and the results were as follows: For hydrothermal stability (Td from DSC analysis), 2 > 3 > 4 > 1 > 5; for colors, 1 was purple-red, 2 was dark purple, 3 was red brown, 4 was dark green, 5 was brown back; for washing fastness, 1 > 2 > 3 ≈ 4 > 5.

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Study of the Qualitative and Semi-quantitative Analysis of Grape Seed Extract by HPLC

by Sílvia Sorolla, Antonia Flores, Trini Canals, Rosa Cantero, Joaquim Font, Luis Ollé and Anna Bacardit

The main aim of this study is to carry out a qualitative and semi-quantitative analysis of tannin extracts as an alternative to the official analysis method ISO 14088 – IUC 32, so that a correlation between the two methods is established.

From the point of view of the chemical composition, tannins are classified into two major groups:

i) condensed tannins, also called flavanols or catechins, and ii) hydrolysable tannins, also called pyrogallic tannins.

Today, the most widely used conventional extracts are quebracho, mimosa, chestnut, and tara. Quebracho and mimosa are condensed tannins, whereas chestnut and tara are hydrolysable tannins.

The following extracts were used in this study: tara powder, commercial mimosa and quebracho extracts and extracts derived from grape seed, containing both condensed and hydrolysable extracts.

The development of this new method will allow a faster and less expensive estimate of the amount of tannins present in a tannin extract.

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