| In the leather dyeing and fatliquoring section, a large number of leather chemicals are added into the water, only 70% (wt%) of them can be absorpted by the wet blue normally, the remanent in the water become pollutants, resulting in the complicated composition and great pollution on leather dyeing and fatliquoring wasterwater. If they are not handled properly, but discharged into the total wastewater directly, not only the burden of biochemical treatment on the total wastewater will increase, but also the resources will be wasted. Flocculation sedimentation method is commonly used in wastewater treatment to remove such pollutants from water in order to reduce the load of biochemical treatment, thus lead to formation of a large amount of sludge. Exploring a kind of special biodegradable flocculants that can separate the available chemicals from the leather dyeing and fatliquoring wastewater, reduce the biochemical load, as well as reduce sludge emissions and the recycled chemicals could be applied to leather filling. The corresponding research about the flocculant has not been reported at present. In order to solve this problem, in this study, a kind of strong cationized keratin flocculant was fabricated using the abandoned Ox hair as raw materials which could be biodegradable and the produced floes could be directly recycled.First, keratin was extracted from abandoned Ox hair in alkaline conditions, followed by cationicing via a low toxicity quaternary ammonium reagent 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA). The FT-IR was used to characterize the structure of the sample, and its thermal properties were studied by synchronous integrated thermal analyzer, the biodegradability were evaluated by natural soil burying method.The results showed that the cationic degree of cationized Keratin was ideal, the cationic degree was increased from 0.79 to 1.55, isoelectric point was increased from 3.65 to 8.12, the solubility had been greatly improved, the thermal stability had also been improved in some extent.The prepared cationizd keratin was used for flocculating the leather dyeing and fatliquoring wastewater. The experimental results showed that the optimum flocculation effect of flocculant was at a moderate dosage conditions, and the corresponding Zeta potential value in the best dosage was close to zero, which indicated that the flocculation process was mainly influenced by charge neutralization, and the flocculatation effect in the acidic environment possessed better flocculation performance, leather dyeing and fatliquoring wastewater was usually acidic, the flocculant was used to treating the wastewater without adjusting the pH of solution. The optimum experimental conditions for small scale of flocculation experiments were that the dosage of cationic keratin was 250mg/L, flocculation time was 4 h, the pH of solution was 4.5, meanwhile, the removal rate of CODCr could be reached to 65%, the removal rate of SS could be reached above 95%, the flocculation effect was ideal.The results of the cationized keratin on the flocculation of several leather chemicals showed that the removal rates of dyes were the most significant, the flocculation rate of two dyes reached above 95%, the flocculation effect of the small molecule aromatic were not ideal, the flocculation rate was only 20%, the flocculation effect of the amino resin tanning agent was ideal, it was about 65.6%, and the flocculation rate of protein filling agent was 73.4%, a theoretical basis was provided by it on the estimate of the flocs and recycling.The flocs obtained by recycling were used to fill the chrome tanned leather after proper treatment. The results showed that the chrome tanned leather filled with the flocs were fullness. Thickening rate was 15.12%, the tensile strength was increased, as well as the softness and fullness, the elongation at break was almost unchanged. The filling performance was ideal. |
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