Химия и химические технологии/5.Фундаментальные проблемы создания новых материалов и технологий

 

Ph.D., Associate Professor Kovalenko M.V.;

Graduate student research assistant Gunko D.N.;

Graduate student research assistant Tarazanov A.A.

St. Petersburg State Technological University of Plant Polymers

 

The Multitrial Method for the Determination of Alpha-Cellulose

 

Abstract

The usage of the vacuum filtration unit PVF-47/NB at the stage of mass washing is proposed to reduce the time needed to determine the content of alpha - cellulose by 25%. As a result of the time reduction the obtained results are more accurate.

Introduction

Alpha-Cellulose is a fraction of the technical cellulose, which cannot be dissolved in the 17.5% solution of NaOH followed by washing [1]. Nowadays there are standard methods of the determination of alpha-cellulose: GOST 6840-78 [2], the standards TAPPI T 203 os-74 [3] and ASTM D 1103-60 [4]. To carry out the cleaning process, the pulp is transferred to a porcelain funnel or a glass filter crucible or filter funnel. Then it is necessary to turn on the vacuum carefully and suck the filtrate in a flask [2].

If the faucet is opened at full capacity, the water-jet pump may not withstand the pressure. Since the fiber wash is carried out at low vacuum in three steps with 25 ml of 9.5% NаОН-solution, each new batch of washing alkali is poured only after the complete removal of the previous one. The duration of washing with alkali has to be around 2-3 minutes. After the removal (suction) of alkali fiber is washed with distilled water in batches [2].

It takes 4 hours to analyze the content of alpha cellulose in three samples and if we take into account the process of the pulp drying at the temperature of 100-105 ºC, it will take 6-7 hours more in accordance with GOST 6840-78. The issue of determining the content of alpha-cellulose was not to lose the pulp at the washing step and to analyze as many samples as possible.

During the process of transferring cellulose to the funnel it is impossible to exclude its losses: the random overflow of mass at the stage of washing. Laboratory assistant, who tries to determine the content of alpha cellulose can face the problem of parallel analysis of several samples of alpha-cellulose, that can take quite  long period of time (especially at the washing step). In addition, not all laboratories have the opportunity to provide the vacuum for several samples because of lack of cranes or the necessity of the constant shifting of the hose from one flask to another. If it becomes necessary to analyze the multiple samples at a time, the laboratory will face these problems using the conventional instrumental base. The serial analysis implies to the appropriate 20-minute interval between the analyzed samples [1].

To solve this problem we need the fundamentally different hardware design which will satisfy the requirements of GOST and make it possible to provide the multitrial approach as well as to reduce the time needed to carry out the analysis and the interval between the analyzed samples nearly by 50%. This is a new requirement, which is dictated by the modern conditions of the experiments, and to fulfill it is necessary to:

1.                 eliminate the "human factor" from the definition of content analysis of alpha-cellulose,

2.                 ensure the simultaneity of the connection of the filtering flasks to the vacuum.

These conditions simultaneously satisfy compliance with GOST

A vacuum filtration device PVF-47/NB (BB), presented in Figure 1 satisfies these standards as well as GOST ones.

39570_1.jpg

Fig.1 A vacuum filtration device

Due to three filtration cells connected to the device which provides the vacuum, the installation makes it possible to wash three samples simultaneously.  The greater capacity of the filter cells provides better capacity of the sample and rinsing with water.

Filter taps allow you to adjust pulp washing speed in the easier way comparing with the water -jet pump, which has to be connected to the water. For the vacuum filtration installation connection to the water is not required.

The experimental verification of the statement about the applicability of the vacuum filtration device consisted of the following: it was necessary to compare two methods of washing the alpha-cellulose after its treatment with 17.5% solution of NaOH in the usual way and also using the vacuum filtration device PVF-47/NB.

Materials and methods

In accordance with the assigned task the determination of the content of alpha – cellulose under GOST has been carried out with the help of a filtering funnel with the water-jet pump and the use of vacuum filtration device for the washing stage.

Washing the pulp with the use of the vacuum filtration device

Pulp was placed in the filtration cell after 45 minutes of treatment with 17.5% NaOH solution. In order to do that the clamp under the funnel was raised. After that the researches took the funnel off the base, put the mesh on it and installed the cell, where they put the pulp mass. After they had turned on the pump, they began doing the water filtration of sample simultaneously with opening of the valve under the funnel. Then the valve was closed and filled with a new portion of water. At the same time the washing of three samples of cellulose was carrying out. After all the Bunsen flask were full, the pump was turned off and the filtrate was poured. Then the samples were drying, and finally it became possible to determine the content of alpha cellulose.

Results

In order to determine the content of alpha-cellulose the air - dry samples of cellulose weighing about 3 g were taken under the certain moisture content.

Baseline data for the determination of alpha-cellulose are presented in Table 1

Table 1

№

M1,gr

M2,gr

W1, %

W2,  %

1

3,0079

3,0045

10,2

9,5

2

3,0062

3,0027

3

3,0065

3,0045

1,2,3 – the number of cellulose sample

M1, M2 - the mass of air - dry pulp sample for the determination of alpha – cellulose using the filter funnel with water-jet pump WF POR 160 and the vacuum filtration device, respectively, gr.

W1, W2 – the moisture content of cellulose for the determination of alpha - cellulose filter funnel with POR WF 160 water jet pump and the vacuum filtration device, respectively, %.

Figures which show the content of alpha - cellulose and the time of the analysis are presented in Table 2.

Table 2

№

α1,  %

α2,  %

T1, h

Т2,  h

1

95,1

94,9

 

4

 

3

2

95,3

95,2

3

94,9

94,7

α1, α2 – the content of alpha-cellulose with the use of the filter funnel WF ERP 160 with a water-jet pump and the vacuum filtration device, respectively,%;

T1, T2 - time spent on analysis with the use of the filter funnel WF ERP 160 with a water jet pump and the vacuum filtration device, respectively, h.

According to the conducted research it was found out that time needed to carry out the analysis using the vacuum filtration device is one hour shorter comparing with the time needed for analysis with the use of a filter funnel ERP WF 160 under the vacuum.

Discussion and conclusions

The device equipped with a vacuum filtration has made it possible to reduce the analysis time and obtain the comparable results. PVF-47/NB (BB) enables to carry out the washing process of three samples simultaneously under vacuum. The advantage of using the device for the vacuum filtration is its usability. There is no need to connect the installation with water. It can be placed in any convenient place. The disadvantage is a little noise of the vacuum pump. At the stage of the washing the alpha-cellulose on PVF-47/NB (BB), the appearance of a small working vacuum 0,35-0,95 kg/cm2 can be observed. Moreover to completely suck the liquid from the sample and create a greater vacuum taps should be opened one by one, closing the previous one.

Despite the minor shortcomings, the use of the proposed hardware design is acceptable for the determination of alpha - cellulose.

 

References

1.                 Оболенская А.В. Лабораторные работы по химии древесины и целлюлозы. - М. : Изд-во Экология, 1991. – 320 c.

2.                 ГОСТ 6840-78 Целлюлоза. Метод определения содержания альфа-целлюлозы. Взамен ГОСТ 6840-54, кроме разд.2 – С.5.

3.                 TAPPI Т 203 os-74

4.                 ASTM D 1103-60

5.                 Азаров В.И Химия древесины и синтетических полимеров. - СПб. : Изд-во СПбЛТА, 1999. – 627с.

6.                 Технология целлюлозно-бумажного производства: справочные материалы в 3т. Т.1 Сырьё и производство полуфабрикатов. ч.2. Производство полуфабрикатов. – СПб. : Изд-во Политехника, 2003. – 633с.

7.                 Никитин Н.И. Химия древесины и целлюлозы. - М. ; Л : Изд-во АН СССР, 1962. – 234с.

8.                  Никитин В.М. Химия древесины и целлюлозы / В. М. Никитин. – М. : Изд-во Гослес-бумиздат, 1960. – 368с.

9.                 Удоратина Е.В. Химия древесины и синтетических полимеров. – Сыктывкар : Изд-во СЛИ, 2007. – 32 с.

10.            Cross C.F. Researches on Cellu lose, Vol. III, Longmans, Green and Company, London, 1912.

11.            Burton J.O. Research National Bureau of Standards  6 :603 (April 1931), RP295.

12.             Launer H.F. ΑSimplified Volumetric Determinations of Alpha, Beta, and Gamma Cellulose in Pulps and Papers J. of Res. N.B.S. 18:333 (1937).