Brightening of grey jute-Mechanism and application

156-160<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" ar-sa"="">Ferric iron in combination with phenolic groups of tannin and phenolic acid lignin imparts grey colour in jute<span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:#0e0e0e;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">. <span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">Treatment with EDTA removed almost all the Fe(III)<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" color:#0e0e0e;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" ar-sa"="">, <span style="font-size:11.0pt;line-height:115%;font-family: " calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" ar-sa"="">improving the brightness significantly but caused over-yellowing of fibres. Evidences presented suggest that the removal of metal ions bound with phenolic groups generated free phenolic-OH which on aerial oxidation caused the over-yellowing. Reducing action of dithionite minimized such oxidation and prevented over-yellowing. Besides, dithionite reduced Fe(lII) to soluble Fe(II), there by enhanced the brightening proce<span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:#0e0e0e;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">s<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">s<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:#454545;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">. <span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">Thus<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:#454545;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">, <span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">the combined action of EDTA and dithionite induced a high brightne<span style="font-size:11.0pt;line-height:115%;font-family: " calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" color:#0e0e0e;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" ar-sa"="">ss and restored the natural yellow colour of jute. Brightening of jute under submerged condition proved uneconomical due to the expenses of post-treatment drying. Treatment at a low level of moisture eliminated the above<span style="font-size: 11.0pt;line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:="" minor-latin;mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:="" minor-fareast;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;="" mso-bidi-theme-font:minor-latin;color:#292929;mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">. This Was done by spraying brightening chemicals on fibres before piling. The prolonged piling time and inherent acidity of fibres favoured the brightening reactions. The resultant fibres were brightened <span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:#0e0e0e;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">a<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:="" minor-latin;color:black;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">ppreciably and the yarn spun thereof was found to be superior in quality compared to control.