ABSTRACT
dissertation for the degree of Doctor of Philosophy (PhD) on specialty
6D072000 - Chemical Technology of Inorganic Substances
Kussainova Marzhan Janbolatovna
Development of technology for purification of phosphoric acid from lead and its
salts via zeolite
Present state of solving scientific or scientific and technological problem
and their relevance.
Phosphoric acid is widely used in various fields of industry of Kazakhstan.
Involvement of low-grade and misbalanced raw materials to the industry results
production of phosphoric acid contaminated with heavy metal salts, that transfer into
phosphate fertilizers and further migrate into soil and water. Therefore there is a
necessity in the purification of phosphoric acid. Sorption method by using cheap and
acid stable natural zeolites is the most effective. Besides this, raising sorption
properties of natural zeolites is possible by modifications of them. Perspective
modifiers are chitosan - an inexpensive naturally occurring biopolymer that contains
functional hydroxyl and amino groups, capable of participating in the process of
cation sorption. Modification of zeolite with chitosan will provide a new sorbent with
sorption properties of zeolite and modifier.
Justification of necessity for performance of scientific and research work.
Nowadays, there is a problem of developing an effective method for purification
of phosphoric acids by using cheap and acid stable natural precipitators with high
sorption characteristics with respect to heavy metals, in particular lead. Many
purification methods of concentrated acids based on the application of expensive
inorganic and organic reagents, associated with the consumption of electricity, with
the creation of special conditions (00C) or with duration and multistage process.
Therefore, there is necessity for obtaining novel sorbents based on natural zeolites
and developing environmentally and economically profitable sorption purification
methods of phosphoric acids by acid stable sorbents that can reduce the concentration
of heavy metals. Methods for producing sorbents of zeolite, modified by chitosan and
sorption purification of phosphoric acid from heavy metals do not require expensive
reagents, huge material and economic costs, can be carried out on the existing
industrial equipments of phosphate companies without their significant
modernization.
The aim of work is to study the sorption processes of lead (II) salts, the effect
of anions NO3-, SO32- and СН3СОО- and cations Cu2+, Cd2+ on the sorption of Pb2+
ions by natural and modified zeolite in phosphoric acid, the ascertainment of
characteristics of the expected chemistry of the process of interaction of heavy metals
with sorbents and determination of optimal conditions for their adsorption by zeolites
with following development of sorption technological schemes of purification
processes of phosphoric acid.
- The research tasks:
- to study the influence of various factors (τ, min .; M, M Н3РО4, S:L), the nature
of anion and corresponding cation on sorption properties of natural zeolite with
respect to cations of lead (II) on model systems «Н3РО4 - Pb(NO3)2 (Pb(СН3СОО)2;
PbCO3) – natural zeolite»; «Н3РО4 - Рb2+- Cu2+ - natural zeolite», «Н3РО4 - Рb2+Cd2+ - natural zeolite», «Н3РО4 - Рb2+- Cd2+ Cu2+- natural zeolite»;
- to determine optimum parameters of sorption process of lead (II) salts by
zeolite, by modified chitosan, from dilute and concentrated phosphoric acids;
- to study the sorption process of Pb (II) cations in the presence of Cu (II) and
Cd (II) cations by modified zeolite depending on the time, the concentration of metal
and acid;
- to study the general regularities and properties of structural changes of sorbents
after sorption by physicochemical methods;
- development of methods and technological schemes of the sorption process of
purification of phosphoric acid from heavy metals, by natural and modified zeolite.
Objects of research.
Thermal phosphoric acid with qualification of "p.c.", zeolite from Shankanay
deposit (Almaty region), modifier for zeolite - chitosan are taken as objects of study.
Also the salts of heavy metals: nitrate, carbonate and acetate of lead (II); 4-aqua
cadmium (II) nitrate; copper (II) nitrate were used.
Subject of research – is the study of behavior and characteristics of lead salts
sorption by natural and modified zeolite from phosphoric acid and development of
sorption technologic scheme of its purification.
Scientific novelty of work is to establish the general laws of sorption process of
lead (II) salts from phosphoric acid by natural and modified zeolite, that result:
- the first time revealed the effect of lead on the salt anion sorption Pb 2+ zeolites
and show that its absorption efficiency sorbent they are placed in the following order:
Pb (NO3)2≥Pb(CH3COO)2>PbCO3;
- it is established that natural and modified zeolite at the same time show
sorption capacity for the cations Pb(II), Cu(II), Cd(II), and also molecular sieve
properties;
- sorption of heavy metals by natural zeolite occurs preferably with outrunning
extraction of Pb cation with larger size (1,26Å), and in a modified zeolite sorption
capacity increases for cations with smaller ionic radius (0,8Å Cu, 0.97 Cd) due to the
presence of functional hydroxyl and amino groups (C6H11O4N)n in a modifier;
- it is found that sorption of heavy metal cations by modified zeolite in acidic
medium occurs through a donor-acceptor interaction of amino group and hydroxyl
OH - group, also by the ion exchange type by substitution of cations that are out of
carcass in the zeolite structure via the process of their hydroxylation and by the ion molecular type, that results high degree of purification of phosphoric acid.
Metrological provision. To execute the work, there are up-to-date devices and
apparatus, the main and auxiliary equipment as well as a number of units necessary
for carrying out technological works. The equipment and technological stock
corresponds to the required standards. There are GOSTs, reagents and certified
methods of analysis. The apparatus used for performing experiments are certified by
the body of metrological control.
The methodological basis. Modern physic-chemical methods of analysis: IRspectrophotometer “Perkin Elmer Spectrum 100” and “Specord M-80”, scanning
electron microscope “JXA-8230” and QUANTA 250 FEG”, derivatograph
“Shimadzu DTG-60”, atomic-absorption spectrophotometer “Perkin Elmer AAnalyst
400”, BET “Quadrasorb SI-KR/MP”, Quantachrome Instruments (USA) were used in
the work.
Connection of work with other scientific research projects.
The dissertational work is carried out in accordance with the themes of scientific
research works (SRW) of laboratory of fertilizers and salts chemistry of JSC
«Institute of Chemical Sciences named by A.B. Bekturov»: «General patterns of
obtaining, physical and chemical properties and design of P-, Si-containing
compounds from natural and secondary phosphate raw materials» (№ G.R.
0112RK002212); «Study of interference of phosphates, humates, inorganic
compounds of transition metal series and sorbents on the composition and properties
of produced products and sorption processes in water-salt systems» (№ G.R.
0112RK00221).
The personal contribution of the doctorant is analysis and generalization of
literature data, the choice of the subject matter of the research and organization,
setting up and carrying out experimental investigations, calculation, analysis and
generalization of the obtained results, preparation of scientific publications.
Approbation of the work. The main results of the work were presented and
discussed at scientific-practical and international conferencies, seminars: XVIII
International conference “Mechanics of Composite Materials” (Riga,2014);
International scientific conference “Technology 2014” (Severodonetsk, 2014);
Conference abroad “Zeolite 2014 - 9th International Conference of the Occurrence,
Properties, and Utilization of Natural Zeolites” (Belgrade, 2014); International
scientific-technical conference “Chemistry and Modernity” (Cheboksary, 2015); VII
International Scientific Conference “ Problems of innovative development of the oil
and gas industry ” (Almaty, 2015);
Publications. The results of the executed work are reported work are reported in
13 scientific publications including:
- 4 articles issued in the journal recommended by the committee on control in
the field of education and science of the Ministry of education and science of the
Republic of Kazakhstan;
- 4 articles issued in international scientific editions entering the data based
Scopus and Thomson Reuters, non-zero impact factor;
- 5 articles and theses issued in international, foreign and republican scientific
conferences, seminars.
The structure and volume of the dissertation. The dissertation comprises
Introduction, 5 sections, conclusion, the list of the used sources. The total volume of
the dissertation makes up 149 pages, 29 tables, 51 figures, the list of 163 references.