| A large amount of kelp residue and wastewater are made from sodium alginate production process. There are a lot of fibers contained in the kelp residue, a small portion was made into feed after drying, most of them were discharged directly, which not only wasted resources, but also polluted the environments seriously. Sodium alginate production wastewater mainly contains a mass of inorganic salts and organic matter such as polysaccharide, formaldehyde, cellulose, protein and pigments etc. If the wastewater was discharged directly, it would have an adverse impact on the aquatic rescources and aquaculture, and even endangered human body health. In this paper, we researched how to treat and recycle the kelp residue and wastewater respectively in the process of sodium alginate production, so the full paper was divided into two parts.1. Kelp waste residue in the process of sodium alginate production was processed such as filtration, hydrolysis, bleaching, drying etc. The refined raw material was modified. A series of carboxymethyl cellulose (CMC) were synthesized under the conditions of different ethanol concentration, amount of alkali, alkalization time, chloroacetic acid dosage, etherification time and temperature. Degree of substitution, rheological properties and structural properties of CMC were investigated, respectively.(1) The degree of substitution of CMC increased significantly with increasing amount of ethanol concentration from55wt%to85wt%(based on the solution), followed by a decrease with further increase in ethanol concentration up to95wt%.(2) With the increase of the amount of alkali and alkalization time, the degree of substitution of CMC shows a decreasing trend after increasing. When the mass ratio of NaOH to cellulose was3:1, the reaction time was60min, the degree of substitution of CMC achieved maximum. (3) The degree of substitution of CMC increased and then decreased with the increase of chloroacetic acid dosage, etherification time and temperature, respectively.(4) Using the kelp residue as raw materials, CMC was synthesized. The optimal conditions for synthesis were as follows:ethanol concentration85%, the mass ratio of NaOH to cellulose3:1, the mass ratio of chloroacetic acid to cellulose3:1, alkalization time60min, etherification time150min at70℃. The DS of CMC was0.62under the optimum conditions.2. The filtered sodium alginate wastewater was treated by electrodialytic method. The optimum conditions of electrodialysis wastewater process were obtained with response surface methodology. Removal efficiency, Dc consumption and current efficiency of electrodialysis were investigated, respectively. And the effects of electrodialysis processing wastewater on the quality of sodium alginate were also investigated.(1) With Box-Behnken central composite method, the optimum operating conditions of the electrodialyzer were obtained as follows:wastewater flow200L/h, opterating voltage40V, volumes ratios of dilute to concentrated wastewater1:1. Under this condition, the actual Dc consumption was0.45KWh/Kg.(2) The removal efficiency of the electrodialyzer increased and then decreased with the opterating voltage, decreased with the wastewater flow, increased with the volumes ratios of dilute to concentrated.(3) The Dc consumption of the electrodialyzer increased with the opterating voltage and the wastewater flow, decreased with the volumes ratios of dilute to concentrated wastewater.(4) The current efficiency of the electrodialyzer increased and then decreased with the operating voltage, decreased with the wastewater flow and the volumes ratios of dilute to concentrated wastewater.(5) Comparing the running water and electrodialysis processing wastewater, with the decrease of the conductivity, calcification effect became better, the extraction yield and viscosity of sodium alginate increased gradually. |
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