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Technology for Isolation of Radionuclide-free Cellulose

#B-852


Development of Conversion Technology for Isolation of Radionuclide-free Cellulose and Nitrolignin from the Straw of Agrocultures as a Method for Rehabilitation and Deactivation of Territories

Tech Area / Field

  • CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
  • ENV-EHS/Environmental Health and Safety/Environment
  • ENV-RED/Remediation and Decontamination/Environment
  • ENV-RWT/Radioactive Waste Treatment/Environment

Status
8 Project completed

Registration date
07.02.2002

Completion date
23.01.2008

Senior Project Manager
Kulikov G G

Leading Institute
Belarussian State University / Institute of Physical Chemical Problems, Belarus, Minsk

Collaborators

  • University of Wales / School of Agricultural and Forest Sciences, UK, Bangor\nNational Renewable Energy Laboratory of National Bioenergy Center, USA, CO, Golden\nFraunhofer Institut Angewandte Polymerforschung, Germany, Potsdam-Golm

Project summary

The Project’s purpose is the development of technology for isolation of radionuclide-free cellulose and nitrolignin from the straw of agrocultures, with simultaneous conversion of a missile fuel oxidizer, as a method for rehabilitation and deactivation of territories.

The state of the art in the research field and actuality of the Project.

A large number of potentially dangerous installations exist in the world which are fraught with risks of accidents of the Chernobyl kind.

The search for pathways to rational utilization and deactivation of radionuclide-contaminated agricultural areas would be one of the most urgent tasks to be performed in order to overcome the consequences of such disasters.

The post-Chernobyl experience has shown that essentially two types of agricultural technologies are acceptable on polluted territories. The first one is based on a regular heavy application of various fertilizers into the soil. This promotes competitive absorption of cations – analogues of radionuclides – by the plants, leaving radionuclides themselves in the soil and decreasing thereby the radionuclide uptake by the plants being used as fodder or for food production. This type of technology is widely used, however, the costs of its application are rather high, and no soil deactivation is achieved. Moreover, it often proves to be economically unjustified after a long period of time from the accident date [Fesenko, S.V., Sanzharova, N.I., and Aleksakhin, R.M. Radiation Biology. Radioecology. 1998, v.38, No.3, p.354].

Technologies of the second type, which are less studied but very promising, are based on cultivation of technical (non-nutritional) plants whose seeds are raw material for obtaining radionuclide-free products (vegetable oils, alcohol). On the territories in Belarus with pollution density up to 555 kBq×m-2 of 137Cs, and up to 55 kBq×m-2 of 90Sr, the culture of rape has already been introduced, and radionuclide-free oil was extracted from its seeds. For similar purposes, technologies of growing soya and flax on such territories are now being developed. Along with obtaining radionuclide-free technical products, a phytodeactivation of contaminated soil, i.e. progressive purification due to radionuclide uptake by the plants, is achieved using this technology [Raskin, I. Environm.Sci. and Technol. 1995, v.29, p.1239]. However, production residues in the form of straw where the major part of radionuclides is accumulated are disposed of, in most cases, by incineration. In the course of this procedure, certain amounts of radionuclides are usually dispersed into the environment with the smoke particles, even if special equipment is used. Thus, a problem of utilization of contaminated straw from the technical agriculture plants does exist.

The impact of the proposed project on the progress in this field consists first of all in a considerable reduction of costs for rehabilitation and deactivation of polluted territories by obtaining additional commercializable products: radionuclide-free cellulose and nitrolignin from the straw remaining after harvesting the seeds. Such an approach to a possible solution of this problem is proposed for the first time.

The cellulose content of straw from such plants as cereals, rape and soya is on the same level as that of wood of deciduous species (ca. 50%). In the case of flax, it attains the value of 80%. An enormous interest in the low-cost and annually renewable raw materials for obtaining fibrous products is actually manifested worldwide [Bowyer, J.L., Stockmann, V.E. Forest Product Journal. 2001, v.51, No.1, p.10]

Advantages of the approach proposed are as follows:

– improvement in economical efficiency of utilization of contaminated land;


– progressive deactivation of the territories;
– minimization of secondary contamination of the territories;
– contribution to the conservation of forest resources;
– localization of liquid radioactive waste within the initial stage of straw delignification followed by concentration, solidification using a known technology, and disposal.

An important feature of the Project is the possibility of using for the process both commercial nitric acid and the so-called ‘missile’ nitric acid – the main component of missile fuel. After nuclear missile disarmament of Republics of the former USSR, large quantities of this ecologically dangerous missile fuel component have been left on their territories. Storage of this material requires special conditions to be created, whereas its utilization is problematic and expensive. For example, ca. 14,000 t of ‘missile’ nitric acid are stored near the western border of the Republic of Belarus, being a potential threat to not only this country itself but to neighbouring countries – Lithuania and Poland – as well. The proposed version of utilization of diluted solutions of this acid will not entail technological or environmental problems.

Competence of the project team.

A half of the team members have formerly been involved in work concerning armament issues. They are experts in missile technologies, in particular, missile fuel production, and in radiation safety. The remaining Project participants are highly qualified specialists in physics and chemistry of cellulose, and in chemical technology. All of them possess wide experience in handling nitric acid and higher nitrogen oxides – components of ‘missile’ fuel. Ten of the twelve team members, including all of the weapons specialists, possess academic titles and degrees. The Project managers are leading specialists in theory and practice dealing with applied aspects of interaction of cellulose and cellulose-containing materials with nitrogen oxide compounds. One can judge about their professional level from numerous articles published in well-known international journals.

Expected results and their application:

– Advantages of the proposed delignification scheme over conventional methods with regard to completeness and selectivity of radionuclide separation from the plant material will be shown and scientifically substantiated. (Task 1).

– The most rational technological parameters will be recommended for the processes of isolation of radionuclide-free cellulose and nitrolignin from contaminated straw of technical agrocultures. Features of using “missile” nitric acid will be determined. (Task 2).

– Technologically and ecologically acceptable schemes will be proposed for bleaching of the isolated cellulose using the same nitric acid oxidizers as those involved in the pulping stage. (Task 3).

– Structural features of cellulose fibres isolated from the straw of various technical agrocultures will be determined, as well as a complete set of mechanical and other performance indices for experimental paper samples prepared from bleached and unbleached straw cellulose, and of its compositions with wood cellulose. Recommendations will be given as to application of various kinds of straw cellulose for manufacture of specific pulp-and-paper products. (Task 4).

– Conditions will be determined for concentrating contaminated acid solutions, as well as alkaline nitrolignin-containing solutions, using membrane technology methods. (Task 5).

– A fundamental technological production scheme will be developed. (Task 6).

Results to be obtained in the course of the Project implementation can be used for the purposes of rehabilitation and deactivation of territories contaminated with radionuclides or heavy metals as a consequence of technology-caused accidents, military tests or military actions, or terrorist attacks. The results will contribute to the development of non-wood material processing technologies aimed at obtaining cellulose.

For the first time, information will be obtained concerning the use of straw from rape and soya as raw materials for cellulose production. The missile fuel oxidizer conversion for production of cellulose and nitrolignin will be of practical importance. While performing the Tasks 1-3, results containing “know how” are expected. The proposed version of utilization of contaminated agricultural residues, and of “missile” nitric acid, has obvious economical and ecological advantages over other known technologies, in particular, incineration of contaminated straw, or ploughing it in. Cellulose value is 4-5 times higher than that of the energy obtained on combustion of the same quantity of cellulose-containing material. Bringing nitrolignin into contaminated soil will enrich it with humin-like substances, prevent wind erosion and radionuclide transport with the dust.

The total of patentable and commercially significant results will serve as a scientific and technological basis for creation of the respective production units.

Meeting ISTC goals and objectives.

The Project is fully consistent with goals and objectives of ISTC, since it provides:

– re-orientation of its participants from among weapons specialists towards peaceful activities by applying their knowledge in the areas of missile fuel and radiation safety to develop and improve technologies of rehabilitation and deactivation of polluted territories, and to solve, at the same time, the problem of conversion of missile fuel;

– assistance for integration of the Project participants into international scientific community, by means of contacts with foreign scientists dealing with development technologies relating to deactivation of territories and cellulose production from non-wood raw materials;

– further progress in applied research and development on elimination of consequences of radioactive environmental pollution, that is of major national and international importance;

– a support for the development of market economy by means of licensing the “know-how” relating to technological operations.

Scope of activities.

Duration of the proposed Project is 36 months. Six tasks are to be performed, the contents and succession of which are set forth above, in the section “Expected Results and their Application”.

Role of foreign collaborators.

The following forms of participation are proposed, agreed upon with the Project Collaborator:

– a systematic exchange of scientific information acquired by the Project participants and discussions of experimental results;


– coordination of reports (annual and final) to be submitted to ISTC by the Project participants;
– realization of joint scientific and practical workshops;
– preparation of experimental samples of paper and investigation of their mechanical properties, as well as structural features of straw cellulose, with the aid of equipment being at the disposal of Collaborator;
– joint publication of the results obtained.

Technical approach and methodology.

Methodological approach to the Project goal attainment is based on preliminary data about the possibility of selective radionuclide extraction from vegetal tissue of annual plants during delignification performed under specific conditions. A more than 200-fold decrease of radioactivity was achieved in target products isolated by this method from heavily radionuclide-contaminated material (65,500 Bq/kg, 137Cs), down to a level acceptable even for foodstuffs. The proposed approach allowed cellulose with good quality indices to be isolated in good yields from the straw of rye and rape. Thus, high efficiency of the approach is experimentally confirmed. Nevertheless, its further development is needed.

A common feature of the Tasks 1, 2, 3 and 5 will be the use of methods of determination of 90Sr, 137Cs, 238, 239, 240Pu and 241Am levels in the soil, starting vegetal material, target products, waste solutions and washings. The results of material balance calculation of radioactivity after each of the technological procedures of vegetal material delignification using different methods will form a basis for realization of the Task 1.

While performing the Tasks 1-3, in parallel with measurements of radioactive isotope levels, chemical composition of the starting raw materials will be determined, as well as yields and chemical composition of cellulose and nitrolignin.

Performance of the Task 2 will require experimental data to be obtained concerning the influence of specific technological parameters on radiochemical purity, yields and quality of the target products. To solve this problem, application of mathematical modelling methods is envisaged.

To elucidate features of using “missile” nitric acid under conditions of the study, investigations will be performed of delignifying and deactivating efficiency of common nitric acid as compared to those of model mixtures of common nitric acid with compounds present in “missile” nitric acid and capable of producing either catalytic (N2O4) or inhibitory (I2, HF, H3PO4) effects.

Task 3 will be fulfilled by experimental adjustment of conditions for cellulose bleaching using two- and multiple-stage schemes. Nitric acid oxidizers and their combinations with conventional bleaching agents will be used.

For comparative characterization of fibres of the cellulose obtained, methods of X-ray phase analysis, IR spectroscopy, optical microscopy, transmission and scanning electron microscopy will be used.

With the aid of the appropriate paper testing instruments, a comprehensive characterization of mechanical and other indices of experimental paper samples will be performed (Task 4).

For concentrating the contaminated acid solutions and the nitrolignin-containing alkaline solutions, reversed osmos method will be used and the respective procedures developed (Task 5).

Based on analysis of the results obtained in the course of fulfilment of Tasks 1-5, a fundamental technological production scheme will be developed (Task 6).

The preliminary results available, competence and skills of the team, as well as the presence of the Chernobyl ‘testing area’ in Belarus, are sound prerequisites to a successful implementation of the Project.


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