Synthesis Of The Novel Adsorbent And Development Of An Integrated Process For Treating Iodine-containing Radioactive Wastewater

With rapid development of nuclear power and industry,water contamination by radionuclides is becoming a pressing global issue.In this work,a novel nano Cu₂O/Cu-doped activated carbon composite,namely nano Cu₂O/Cu-C,was successfully synthesized for the removal of radioactive iodide ions(I^-)from simulated radioactive wastewater.Meanwhile,a novel countercurrent two-stage adsorption process was tailor-designed with the aim to maximize the adsorption capacity of nano Cu₂O/Cu-C and the decontamination factor(DF)of I^-.This process could help to effectively solve the problems of low usage rate encountered in the conventional single-stage adsorption process.For large-scale application,an innovative manufacturing process was also developed with the features of simple configuration,mild operation condition,easy operation,allowing for mass production of the nano Cu₂O/Cu-C adsorbent.To further validate the performance of nano Cu₂O/Cu-C adsorbent,a lab-scale integrated novel countercurrent two-stage adsorption-microfiltration was designed and operated with simulated radioactive wastewater.This modular equipment was able to provide technical support for the emergent treatment of water decontaminated by sudden nuclear accidents.The following conclusions could be drawn from this study:(1)Coconut shell activated carbon,natural clinoptilolite,nano Cu₂O and micro-Bi₂O₃ were confirmed to have certain adsorption properties for I^-.The maximum adsorption capacities for I^-were 5.26,0.20,3.23 and 7.87 mg/g.Nano Bi₂O₃ synthesized by a hydrothermal method with 200-600 nm edge length exhibited an adsorption capacity of 12.4 mg I^-/g,which was higher than commercially available micro-Bi₂O₃.(2)The novel nano Cu₂O/Cu-C composite was firstly synthesized by a simple and efficient hydrothermal method for treating simulated wastewater with radioactive iodide ions.Nano Cu₂O/Cu-C possess an excellent adsorption capacity of 41.2 mg I^-/g.More importantly,not secondary pollution was generated during adsorption,i.e.this adsorbent was environmentally friendly.The observed high adsorption capacity of nano Cu₂O/Cu-C could be attributed to complexation and precipitation of iodide ions.(3)A novel countercurrent two-stage adsorption process was successfully developed with the synthesized nano Cu₂O/Cu-C as adsorbent.The decontamination factor achieved in this process was about 8.76 times higher than that in the conventional single-stage adsorption process.Furthermore,in order to simulate,while to predict the quality of effluent from the proposed process,a Langmuir isotherm-based modeling system was established.The experimental results could be well described the proposed models.(4)For mass production of the nano Cu₂O/Cu-C adsorbent,a simple and highly efficient manufacturing method was developed.An innovative integrated novel countercurrent two-stage adsorption and microfiltration system was also designed and operated to assess the performance of the mass produced nano Cu₂O/Cu–C and effectively seperate the used adsorbent.The constantly good effluent quality was achieved with more than 90%of I^-removed at a concentration of 2.00 mg/L.Moreover,slower membrane fouling was observed.This work clearly demonstrated the engineering feasibility of the proposed integrated process in treating iodine-contaminated radioactive water.