Preparation Of Polya-luminum Complex With Cationic Keratin And Its Flocculation On Leather Dyeing-fatliquoring Wastewater

Tannery wastewater is one of the extremely difficult industrial wastewaters.Due to the large number of processes in the tanning industry,complex pollutants,high chroma,large fluctuations in water quality and water content.In dyeing-fatliquoring section,the wastewater was high-COD_Cr,high-chroma and Cr containing,making the dyeing-fatliquoring wastewater fail to reach the standard of workshop discharge standard,because of it contains plenty of unabsorbed chemical additives.Therefore,it was significance to explore a reasonable method to pretreat dyeing-fatliquoring wastewater.In this study,the cationic keratin and polyaluminum sulfate flocculant was synthesized by polymerization reaction method.Reach the national integrated discharge standard,ease the burden of biochemical treatment,and reuse the chemical reagents in waste as well.Furthermore,in this way,we can explore the reusing effect of the floc and the supernatant.The cationic keratin and polyaluminium sulfate flocculant was synthesized by keratin,3-chloro-2-hydroxypropyl trim-ethyl ammonium chloride and aluminum sulfate as materials.Then the cationized keratin polymerization reaction with aluminium sulfate in the ratio of 1.0:1.6 was used to conduct at p H 4.0 and at 55?for 1h,at room temperature for 4h.The structure of copolymer was characterized by FT-IR,GPC,and the properties were analyzed by TG and DSC.It turned out that keratin,3-chloro-2-hydroxypropyl trim-ethyl ammonium chloride and aluminum were combined,the Mn was 3612,the Mw was 3643,the Mp was 3731,and the thermal stability has improved.When pH value in the range of1.0⁷.0,the amphoteric keratin can be dissolved.And the isoelectric point of flocculant was 2.61.The method of single factor controlled was used in this paper.It not only analyzes the cationic keratin flocculant and polyaluminum sulfate flocculants how they affect flocculation effect,but also explored how different PH value and flocculating time impact on flocculation effect.Experiments showed that the cationic keratin and polyaluminum sulfate complex flocculant has the best removal effect on dyeing-fatliquoring wastewater.When the dosage was 2.20 g/L,pH=4.0,the flocculation time was 2.0 h,temperature was 25°C³5°C,the removal rates of COD_Cr,SS,total Cr,color,and turbidity in dyeing-fatliquoring wastewater were:87.00%,96.58%,95.72%,99.30%and 97.99%,respectively.From the experimental results,it was concluded that the cationic keratin and polyaluminum sulfate complex flocculant has strong COD_Cr and chroma removal capability,and total Cr reaches the workshop emission standard.The flocs recycled into the fatliquoring stage for use as leather fillers.The experimental results show that the thickness,tensile strength,tear strength,and elongation at break of the crust after filling with floc were increased by 10.00%,197.20%,15.20%,and 24.72%,respectively.It was proved that the flocs obtained by flocculating the cationic keratin and polyaluminum sulfate complex flocculant dyeing-fatliquoring wastewater can be effectively reused.At the same time,the flocculated dyeing-fatliquoring wastewater supernatant was reused into the crust dyeing and fatliquoring section as process water.It is proved by the practical experiences that the crust produced by supernatant had normal performance and it can be recycled as well.