POTENTIAL OF BIOSORPTIONAL TECHNOLOGIES Текст научной статьи по специальности «Электротехника, электронная техника, информационные технологии»

CHEMISTRY

POTENTIAL OF BIOSORPTIONAL TECHNOLOGIES

Doctoral Aronbaev S. D.;

Doc. Techn. Sci., Professor Nasimov A. M.;

Ph. D., Associate Professor Aronbaev D. M

Uzbekistan, Samarkand, Samarkand State University named after A. Navoi

Abstract. The article shows the potential of bio-sorptional technologies for extraction of heavy metals, radionuclides and other toxic substances from aqueous solutions. Example preparing solid biosorbents on based yeast Saccharomyces cerevisiae, which have magnetic properties. Examples of using the magnetic biosorbent at static and dynamic modes in the magnetic field of the solenoid.

Bio-sorptional technology involves the use of living or dead organisms of different taxonomic groups, are increasingly used for wastewater, surface water and drinking water from heavy metals, radionuclides, organic and other pollutants. At the same time, the commercialization of bio-sorptional technologies hinder not only relatively low sorption capacity of most microorganisms, but also technical problems related to the maintenance and regeneration of native biosorbent. Part of the problem is solved by immobilization of biomass on a solid inert carrier such as carbon, zeolites, vermiculite or by incorporating them in an alginate gel. In this case, it becomes possible to use dynamic sorption process, so-called "columnar variant." However, it significantly decreases biosorbent sorption capacity compared to static biosorption. In addition, problems persist regeneration biosorbent and replace it with the full elaboration.

The present study aims to support the development of "smart" sorption material having magnetic properties vary depending on the intensity of the magnetic field. This effect is achieved in that implemented joint immobilization of biomass of yeast Saccharomyces cerevisiae and synthetic magnetite nanoparticles into gel of calcium alginate. Then, while maintaining the advantages of a solid biosorbents newly synthesized smart sorbent becomes magnetically. It is facilitate its technological application. For this purpose, magnetite was prepared by technology providing homogeneous magnetic particle synthesis using reaction

2Fe+3 + Fe+2 + 8NH4OH = Fe3O4|+ 8NH4+ + 4H2O

The main characteristics required of magnetite nanoparticles - it

• lack of residual magnetization;

• uniformity of dispersion;

• high values of the magnetic susceptibility.

Obviously, the magnetic susceptibility of magnetite or other magnetic nanocomposite materials, primarily determined by its crystal structure, which depends on the reaction conditions of its preparation. But from the reaction conditions also depend nanoparticle sizes obtained. We investigated the possible factors influencing the formation of magnetite nanoparticles: - the molar ratio of iron salts; nature and concentration of alkali; synthesis conditions - the temperature and the intensity of mixing. The experimental results are presented in figures 1-4.

We have shown [1]:

1. The dependence of the magnetic susceptibility of the molar ratio of iron salts is an extreme with a pronounced maximum at the molar ratio of Fe (III) and Fe (II), equal to 2.5 -2.75: 1 (stoichiometric had to be 2: 1).

We studied molar ratio salts of iron (III) to (II) varied in the range of from 1 to 4. We used iron (II) in the form of chloride and sulfate. When using FeCl2 obtained higher rates of magnetic susceptibility.

2. When using a alkali such as KOH, NaOH and NH4OH preference should be given to weaker electrolyte. It was found that the magnetic susceptibility of magnetite nanoparticles decreases in the order: NH4 +> Na +> K +, ie, than more force of electrolit electrolyte selected for the deposition of magnetite, the less magnetic susceptibility.

3. The increase in temperature increases the rate of formation of magnetite and its maximum yield can be obtained in the temperature range 30 - 40 C. At a temperature of 40 ° C synthesis time is less than two minuts.

4. At increase in speed of hashing size obtained magnetite nano particle decreases, reaching optimum dimensions at 1000 rev / min.

5. At increasing the concentration of iron salt in the reaction medium is observed increase in the average particle diameter.

12 3 4

мольное соотношение Fe(lll) : Fe(ll)

Fig.1. The dependence of the magnetic Fig.2. The dependence of the magnetic

susceptibility of the molar ratio of iron salts susceptibility of the nature of the alkali.

Fig. 3. Dependence of the time of the magnetite precipitation reaction at different temperatures: 1 - 10 ° C; 2 - 20c C; 3 - 30° C; 4 - 40 ° C.

Fig. 4. The dependence of the dispersion magnetite from concentration of iron salts and a stirring speed of1000 r / min.

We optimized conditions for reception of synthetic magnetite nanoparticles:

Terms:

• salt concentration of iron of 0.5 wt.%;

• molar ratio of iron salts (III) and (II) 2,5 - 2.75: 1;

• concentration of NH4OH - 8 wt%;

• t = 400C.

Obtained by this formulation magnetite nanoparticles have a mean size of about 10 -

20 nm.

The synthesized magnetite nanoparticles have been used by us in subsequent experiments to produce magnetic fluids of demonstration experiments with them and creating bio-sorptional composite materials for remediation of waste water.

Previously, our research and analysis of the adsorption properties of the native cell walls of the yeast Saccharomyces cerevisiae showed them acceptable sorption characteristics that allow them to use as a raw material for producing cheap biosorbent [2]. Therefore, to give them magnetic properties, we proceed as follows:

To a mixture of 1.0 g of magnetite, and 0.8 g of alginate is added with stirring 20 mL of 0.25 M phosphate buffer pH 6.86 and was introduced into a mixture of 800 mg of yeast cell walls. After 15 minutes of vigorous stirring the resulting slurry with using syringe dripped into 0.2M calcium chloride solution. The resulting alginate beads of 1-1.5 mm diameter with immobilized yeast biomass left in the solution for 30 minutes for curing. The pellets were washed, keeping them at the bottom of the vessel by a permanent magnet.

Evaluation sorption capacity magnetic biosorbent relative to heavy metal ions (Pb

+ 2

+ 2 2

Cd + 2, Cu + 2) was performed by the method of equilibrium concentrations. For this purpose, to 100 ml of model solution of heavy metal ions of known concentration (5-100 mg / L) was added 1 g of magnetic biosorbent, the contents were shaken on a horizontal shaker at a frequency of 150 rev / min for 3 hours. Sorption capacity of magnetic biosorbent found by

difference of ion concentration of heavy metal in the initial and final solutions, taking into account the volume of solution and weight biosorbent. Measurements of the concentrations of these ions were performed using an atomic absorption spectrophotometer "Saturn-1". Preliminary studies have found that the maximum adsorption capacity of «smart» material in static adsorption calculated from the Langmuir equation is: Cu - 25, 60 mg / g; Cd -34.48 mg / g; Pb - 125 mg / g; U - 183,3 mg / g; phenol - 18.9 mg / g. (Table 1)

Table 1. Sorption characteristics of magnetically biosorbent based on the cell walls of yeast Saccharomyces cerevisiae

Metal ions Calculations based on the linearized Freundlich equation lgq = g (lgK + lgC) Calculations based on the linearized Langmuir equation 1 1 1 — =--1-- q Qmax bQmaxC

n K R2 Qmax, mg/g b R2

Pb (II) 0,598 2,951 0,9002 125,0 0,0131 0,9866

Cd (II) 0,390 6,025 0,9797 34,48 0,0331 0,8409

Cu (II) 0,380 3,980 0,9840 25,60 0,0780 0,9310

U (VI) 0,584 6,31 0,9476 183,3 0,2766 0,9898

С6Н5ОН 0,589 1,650 0,9804 18,9 0,7405 0,9987

The biosorbent with magnetic properties allow more technological operation for concentrating and removing pollutants from solutions since they allow to carry of process in a static mode sorption (for example, in a large vessel or reactor) and facilitate its removal from the reactor for regeneration or disposal (Fig. 6).

Fig. 5. Magnetically biosorbent. a) the retention of a permanent magnet biosorbent

Fig. 6. Sorption of heavy

metal ions in the magnetosphere managed biosorbents

Fig.7. 3.Dynamic mode of sorption in a magnetic field of a solenoid

Application magnetically biosorbent in dynamic mode sorption also has a number of technical advantages. For example, the biosorbent may be in a compact state in the form of a filter in a magnetic field of a solenoid (Fig. 7).

In a case his "siltation" or for need to replace, the current the solenoid is switched off and biosorbent is shaken . We can make it prevention. When the current to the solenoid coil,

the magnetic particles are formed filter and biosorbent is ready again. Table 2 presents the results of laboratory testing technology bio-sorptional wastewater treatment using dynamic mode. The size of the biofilter in the magnetic field of the solenoid: 1.5 x 5.0 cm; filtration rate 1.5 ml / min.

Table 2. Sorption of heavy metals from multicomponent solutions

Elements Cu Cd Pb Zn Mn Fe Co Ni

Initial concentration, 11,6 8,4 18,8 14,5 3,8 6,6 4,8 9,5

mg / l

Concentration of the 2,2 0,04 0,18 0,14 0,36 0,40 0,33 1,47

solution after treatment,

mg / l

The recovery rate,% 81,0 99,5 99,1 99,0 90,5 93,9 93,1 84,5

Maximum permissible 1,0 0,01 0,1 5,0 0,1 0,3 1,0 0,02

concentration in drinking

water, mg / l

Thus, we have demonstrated the principled feasibility of the implementation of processes for bio-sorptional concentration, separation and recovery of heavy metals, radionuclides, toxins for:

- Hydrometallurgical, mining and ore processing industry for the extraction of non-ferrous and precious metals and associated;

- In the nuclear industry;

- Environmental protection measures;

- Analytical chemistry for concentration toxicants and their subsequent determination at maximum permissible concentration level and below. Prerequisites are being created for the commercialization of bio-sorptional technologies that can replace the whole cycle of production, use expensive sorbents of natural or synthetic origin in various industries.

REFERENSES

1. Aronbaev D.M., Aronbaev S.D., Nasimov A.M., Vasina S.M. i dr. Sintez i issledovanie superparamagnitnyh svoystv nanochastic magnetita i magnitnyh zhidkostey na ih osnove // Nauchnyy Vestnik SamGU , 2013, №5. - S.97-101.

2. Nasimov A.M., Aronbaev S.D. Biosorbciya ionov svinca, kadmiya i medi osadochnymi drozhzhami Saccharomyces cerevisiae // Ekologicheskie sistemy i pribory, 2011, №2. - S.3-7.

3. Aronbaev S.D. Primenenie magnito-upravlyaemyh biosorbentov dlya koncentrirovaniya ekotoksikantov iz vodnyh rastvorov v analiticheskih celyah // Materialy Mezhdunarodnogo molodezhnogo nauchnogo foruma «LOMONOSOV-2014»— M.: MAKS Press, 2014.