Study On Dechromisation For Extracting Feed Collagen Peptide From Leather Waste

Environmental pollution is increasingly serious with the development of the leather industry.Abandoning the chrome shavings randomly, produced during leather processing, not only wastesresources, but also will cause environmental pollution. Therefore, how to make use of theseby-products effectively has been an urgent problem.The key problem of recycling leather waste is separating chrome from collagen fiber anddechroming. H2O2-C2H2O4method and CaO method were used to remove chrome from leatherwaste. Collagen peptide, obtained by dechroming, containing various amino acids, and in whichchrome content met the demand of GB13078-2001(Hygienical standard for feeds), can beapplied to feed industry to supply abundant nutrients for animals. And high-viscosity collagenpeptide can be added to aquaculture feed as adhesive.H2O2-C2H2O4method is firstly oxidization of part of the chrome(Ⅲ)to chrome (Ⅵ) bystrong oxidizability of hydrogen peroxide in alkaline conditions to isolate chrome from collagenfiber. Then oxalic acid, replacing collagen carboxyl and reacting with chrome(Ⅲ), forms freestate chrome compound. To achieve the purpose of further dechroming,[Cr(C2O4)3]3-isabsorbed by ion-exchange resin. The optional experiment conditions were got by single factortest and orthogonal test, were as follows: ratio of material to liquid1:10,7.5%NaOH and75%(v/w) H2O2solution(30%) was added in leather waste and reaction lasted40min at20℃;secondly, leather waste was washed completely whose pH value was close to neutral field, ratioof material to liquid1:10,20%C2H2O4was added to react2h at80℃; at last,717#anionion-exchange resin was added to absorbed [Cr(C2O4)3]3-. The amount of717#anionion-exchange resin is one and a half times as much weight as collagen peptide. In optionalconditions collagen peptide yield was67.35%, while chrome content and protein content were12.20mg/kg and98.64%(on dry basis).CaO method is that chrome(Ⅲ)reacts with hydroxyl forming chrome hydroxideprecipitation to separate chrome from collagen peptide while collagen fiber is hydrolyzed in hotalkali solution. The optional experiment conditions were got by single factor test andorthogonal test, were as follows: ratio of material to liquid1:10,9%CaO was added in leatherwaste and reaction lasted8h at90℃.In optional conditions collagen peptide yield was45.07%,while chrome content and protein content were14.08mg/kg and93.79%(on dry basis).Hexavalent chromium waste water processing conditions were got by reaction principle and single factor test. Sodium pyrosulfite was added to react30min in the pH value of2. Andthe amount of sodium pyrosulfite is three and a half times as much weight as chromium.Adding7%collagen peptide to aquaculture feed can lower the loss rate of feed to4.29%inseawater and6.54%in purified water. Crystal lysine embedded in collagen peptide cansignificantly decrease the dissolution rate of lysine in water. When adding25%collagenpeptide, the dissolution rate of lysine is17.43%.