Research On The Recovery And Reuse Of Sodium Alginate In Printing Wastewater

Printing paste was the carrier to transfer the the dyes and chemicals into the fabric in the color paste,which has great significance for the printing processing.Sodium alginate as a natural polymer compound and was the most important paste raw material which has good paste-forming properties and high color yield,and was especially suitable for reactive dye printing.The sodium alginate paste was dissolved in water after hot and soaping washing which formed a printing wastewater with high viscosity,high organic content and complex composition.The recovery of sodium alginate in the printing wastewater can not only reduce the burden of wastewater treatment,but also realize the value reconstruction of resource materials in the printing wastewater.By referring to the method that sodium alginate extracted from the kelp,the sodium alginate recovered from printing wastewater was studied.A method was constructed which consist of extraction,purification and bleaching for recovering sodium alginate in printing wastewater,optimized the recycling process and determined the best process.The study found that the recovery sodium alginate chemical structure G/M was 0.48.During the recovery process,sodium alginate was degraded to some extent,and the degree of polymerization and viscosity decreased.for the recovery of sodium alginate was:pH 9.5,sodium hypochlorite dosage was 0.01 g/mL,time was 30 min,the whiteness can reach 58.70 after bleahching,The best decalcification process was:tow acid washing,washing time was 90 min,washing pH was 1.6,the calcium content of the recovered alginate sodium was 157.6 ppm after acid treatment.The yield of the recovered sodium alginate was 30.35%under the best process.The calcium alginate gel beads adsorbent(CA)was prepared by using recovered sodium alginate as basic material and used for adsorbed heavy metal ions.Taking the heavy metal ion copper ions commonly found in wastewater as an example,the effects of pH,initial concentration,heavy metal ions and the amount of adsorbent on the adsorption effect were investigated.The study showed that adsorption were followed second order kinetics and Langmuir adsorption isotherm models,the reaction process was endothermic.The removal rate can reach more than 90%under the following conditions:was 100 mg/L,pH 5.4,the dosage was 1.2 g/L,initial concentrations was 100 mg/L and adsorption time was 300 min.The calcium alginate/activated carbon beads(ACCA)adsorbent was prepared by using recovered sodium alginate as basic raw,and was used treat dyes,the adsorption capacity of methyl orange and methylene blue was investigated.It was found that the adsorption process of adsorbents on dyes accorded with the second-order kinetics and Langmuir adsorption isotherm model.The results showed that with the pH value decrease,the removal rate of anionic dyes will be significantly improved;while the pH value increases,the adsorption performance of cationic dyes will be significantly improved.When calcium alginate entrapped activated carbon can improve the adsorption capacity with anionic dyes,under the conditions with the adsorbent dosage was 5 g/L and the initial dye concentration was 100 mg/L,at 30℃,the maximum removal rate of methyl orange dye is 82.5%,and the removal rate of cationic dye methyl blue can reach more than 90%.