Thesis Proposal

The Petroleum and Petrochemical College

Chulalongkorn University

Thesis title :

Adsorption of surfactant on fiber paper related to paper recycling

Thesis for :

Master degree in Petrochemical Technology

Name of student : Suvena Somabutr

Student ID. Number : 4171033063

Name of advisor : Prof. J. F. Scamehorn

Name of co-advisor :

Asso. Prof. Kunchana Bunyakiat

Dr. Kitipat Siemanond

Academic year : 1998

Date of preparation : 15 March 1999

Student signature :

Approved by :

Background

Introduction

The majority of the technique of deinking process in paper recycling basically has 2 types ; flotation and washing.

This research will concentrate only on adsorption isotherm which is in part of flotation deinking process. Generally, we choose surfactants as base separation for flotation because of 3 main advantages;

  1. low-energy : The process does not require any energy. Because the process is not highly exothermic or endothermic reaction and heat of solubilization is nearly zero.
  2. Non-toxic : Even though cationic surfactants are the most suitable for negative charge surface on paper but it is non-biodegradable. Then this research will focus on mechanism of anionic surfactant on negative surface and calcium as an activator for safe environment.
  3. Delicate : Mild to skin and material to separate, easily biodegraded materials can be treated.

Froth flotation will separate ink from fiber by adding fatty acid (eg. Oleic acid). Calcium ion is added as an activator for helping adsorption mechanism, then air is sprayed through the solution. The dissolved material adheres to the adsorbed surfactant layer around the air bubbles and is carried up to the foam at the surface of the liquid. The last step is skim bubble off, the ink particle also detach from the paper, as shown in the figure below.

At the right condition, the good micelle will form on the ink. The controlled parameters are pH, type and concentration of surfactant, point of zero charge (pzc) and zeta potential.

 

Literature survey

In addition to washing process, flotation deinking is used for paper recycling. M. Rutland, R. J. Pugh [3] studied mechanism of surfactant and calcium in adsorption by surface force and coagulation technique. The surface force technique concerns the interaction of fatty acid flotation collectors and calcium activator with a negative charged mica substrate at high pH. Since the surface of ink particle is enriched by negatively charged group.

This result implies that under alkaline condition, it can be concluded by 3 ideas, shown in the figure below, which are

  1. direct Ca2+ bridging : The calcium could only operate as bridging agents if they can specifically bind to the surface, as well as to the carboxylated fatty acid.

  1. Calcium soap precipitation : When fatty acid concentration and calcium concentration are quite high. It will attach each other which we call precipitation. Finally calcium soap precipitation (flakes) will form micro-encapsulation with ink particle or “heterocoagulation”.
  2. Calcium ion destabilization mechanism : The “calcium dehydration/ destabilization mechanism” occurs as hydrophobic aggregate.

 

After that the improvement of technique to enhance efficiency of process is discovered. Loreen D. Ferguson [2] studied deinking chemicals for support deinking paper recycling.

Sodium hydroxide (NaOH) : used to adjust pH, sponify or hydrolyze the ink resin. The alkaline environment is often reported to swell the fibers. The pH conventionally used for pulping is 9.5 - 11.0 and fiber will be more flexible. The amount of caustic soda and others added on system should be custom optimized for maximum performance. Adding NaOH on wood-containing cause alkali darkening. The alkalinity have affected on brightness afer pulping and flotation deinking.

Hydrogen peroxide (H2O2) : used to decolorize the chromophores generated by the alkaline pH in wood-containing pulper.

H2O2 + NaOH Û HOO- + Na+ + H2O

at pH of 10.0 - 11.5 and Temperature of 40 - 80OC

HOO- (perhydroxyl anion) is used as the active bleaching agent. The best use of peroxide is to maximize HOO- and control important factors such as raise pH, raise temperature, reduce side reaction by reducing heavy metal ion, increase peroxide concentration. The decomposition of peroxide can be reduced by adding of stabilization agents such as chelats and sodium silicate.

Chelating agents : such as DTPA diethylenetriaminepentaacetic acid, EDTA ethylenediaminetetraacetic acid) Chelant is used to form soluble complex with heavy metal ions. But DTPA and EDTA in some country are banned because effluent stream into the aquatic will harm aquatic life.

Sodium Silicate (Na2SiO3) : or water glass is used as a 41.6O Baume solution of sodium metasilicate which contain equally of SiO2 and Na2O. Alkalinity about 11% NaOH. Silicate, is often referred to a peroxide stabilizer, are formed by a colloidal structure with the heavy metal ions and aids in deinking by preventing the ink from redepositing on the fiber surface. It is most widely used in laundry soap. The sodium silicate solution is a source of alkalinity derived from hydroxyl group as well as a pH buffering agent.

Na2SiO3 + H2O Û 2Na+ + OH- + HSiO3

The other quality of sodium silicate is help more brightness but it cause scaling, fouling.

 

R. N. RAO and P. Stenius [4] who found A model printed of dry ink has 3 layers: primary, secondary and tertiary layer. Mechanical force in flotation alone cannot successfully remove primary ink layer in direct contact with fiber. Then adding of surfactant will help to soften the ink and affect the ink/fiber interaction, complete release ink will occur. The surfactant that is used in experimental is mostly fatty acid (eg. Oligoethylene-oxide alkyl ether surfactant) and calcium soap. Calcium soap is helped to remove ink by precipitation, agglomerate and attach to air bubble.

In the experiment any type of force (detachment of ink without shear force, with shear force, mechanical shaking) is applied to help deinking. The 100 percent release ink was achieve by both mechanical actions and at high surfactant concentration with each surfactant.

 

New technique for deinking of Wayne F. Carr [5] is take experiment in removing difficult-to-disperse ink in waste paper. Conventional deinking process of washing and flotation are not very effective at reclaiming speck-free-fiber.

 

 

 

Characteristics of the contaminant

Ink have traditionally consisted of colored pigments for transporting fluidity. Some modern inks consist of fine pellets fixed by fusion. Approaching to ink binder (toner) removal undertaken during the past few years can be group into 2 catagories.

  1. Ink binder removal from fiber with combination of mechanical dispersion and removal. First mechanical dispersion make particles broken into small pieces and additional step for physical removal such as screening, flotation, reverse-flow, washing. Second removal step, screening separates by differences in size and stiffness. Centrifugal by differences in specific gravity, along with 2 types of particle : heavier and lighter than water. Screening with the fiber slotted basket opening down to 0.006 inch (150m m), the large particle is not effectively remove. Reverse-flow cleaner in this experiment are not very efficient. Even though some of the particle may have low density. Forward cleaners appear to have a very high removal effective attibuted to the shape of the particle.
  2. Ink binder removal from fiber with chemical agglomeration followed by removal : A process for absorbing electrostatic toners on polystyrene from prills. Then repulp with an agglomerating chemical formulation, the toner agglomerates are removed by pressure screens, provided the slots.

Trend in new system design

  1. Agglomeration chemical pulping 10%, Cleaning screening 3%, Washing 3%, Two stage forward cleaners 0.8%, Reverse cleaning 0.8%, Washing 0.8%
  2. Pulping 16%, Cleaning screening 3%, Forward reverse cleaning 1%, Washing 1%, Dispersion 35%, forward cleaning 0.8%, Washing 0.8%
  3. Pulping 16%, Cleaning screening 3%, Flotation 1%, Forward reverse cleaning 0.8%, Screening 1%, Washing 0.8%, Dispersion 35%, forward cleaning 1%, Washing 1%

 

 

 

 

Reference

  1. Riviello, Jr., A.E., 1997, “Surfactant behavior in the mechanisms of ink removal from secondary fiber in flotation deinking”, Ph.D. Thesis, University of Oklahoma.
  2. Ferguson, L. D., 1992, “Deinking chemistry : Part I”, TAPPI Journal, 75(7), pp. 84-88.
  3. Rutland,M. and Pugh, R. J., 1997, “Calcium soaps in flotation deinking; fundamental studies using surface force and coagulation technique”, Colloids and Surfaces A : Physicochemical and Engineering Aspects, 125(1), pp. 33 - 46.
  4. Rao, R. N. and Stenius, P., 1998, “Mechanisms of ink release from model surfaces and fiber”, Journal of Pulp and Paper Science, Vol. 24, No. 6.
  5. Carr, W. F., 1991, “New Trends in deinking technology removing difficult inks from wastepaper”, TAPPI Journal, 74(2), pp. 127-132.

 

Objectives

  1. To study the adsorption isotherm of C8 (sodium octanoate) and SDS (sodium dodecyl sulphate) on the fiber paper.
  2. To investigate the type of surfactants that are suitable for deinking recycling paper.
  3. To investigate the pH conditions that suitable on the adsorption of surfactant.
  4. To measure the equilibrium adsorption isotherm.
  5. To understand the mechanism of surfactant/calcium adsorption on the fiber.
  6. To understand how surfactant and calcium differ on the two different surfaces (ink and fiber).
  7. To particularly understand the synergism in adsorption between surfactant and calcium.

 

 

 

 

Scope of Research Work

This thesis research work focuses on the adsorption of surfactants and calcium on fiber paper at equilibrium. The data from experiment will be ploted to analyze the adsorption isotherms of surfactants on fiber paper. The objective of work is to understand the perspective on the importance of understanding the adsorption mechanism of surfactant and calcium in flotation deinking.

This thesis will find the proper type of surfactants for adsorption on fiber paper. Then sodium dodecyl sulphate and sodium octanoate are studied in model plant. The activator, Ca2+ from calcium chloride is used for helping adsorption. The pH condition in the experiment will be varied by sodium hydroxide (NaOH).

 

Methodology

Design and experimental setup

The equilibrium between surfactants and calcium will be studied in test tubes.

 

Method for preparing surfactant (SDS, C8)

  1. Dissolve surfactant into distilled water.
  2. Filter through a fritted glass filter (sintered glass)
  3. Hold it overnight in a refrigerator to allow crystal to fall out.
  4. Filter the precipitated solution through a fritted glass filter.

The second step (reprecipitate surfactant by using methanol)

  1. Dissolve crystals in 100%HPLC grade methanol.
  2. Warming up methanol slightly to enhance solubility of the surfactant.
  3. Leave the solution overnight in the freezer to introduce crystallization.
  4. Filter the surfactant crystal.
  5. Determine the crystals under vacuum overnight.
  6. Determined the purity of the recrystallized surfactant by using HPLC.
  7. Find the purity of recrystallized surfactant by using quantitaive method.

 

Method for prepare fiber [1]

  1. Pulping common office paper (Xerox 4200 DP 20 lb.) at 5%consistency for 20,000 beats at 3000 rpm.
  2. Wash over 140 mesh screen to remove all fillers and extraneous ions until Calcium concentration in the supernatant was less than 0.1 ppm.
  3. Pressed to remove excess water and was oven dried at 50OC. The surface area of the dry fiber approximately 1.51 m2/g.

 

 

Method for obtained adsorption isotherm (solution depletion method)

  1. Mix 1.8 g of dried fiber with 30 ml of solution.
  2. Allow to reach equilibrium about 3 days with occasional agitation and centrifuged.
  3. Analyze concentration of surfactant and calcium concentrations in the supernatant liquid when it reach equilibrium.

 

Experimental procedures

Controlled parameters

The surface area of fiber must be the same in each batch. The type of paper must be the same. The concentration of calcium from paper must be less than 0.1 ppm.

 

Variable parameters

The variable parameter is pH value and type of surfactant which vary in this research to study the adsorbed concentration of surfactant versus equilibrium surfactant on fiber.

 

Methods of chemical analysis and measurement

The concentration of sodium octanoate (C8) adsorb on fiber paper is detected by total organic carbon analyzer. The concentration of sodium dodecyl sulphate (SDS) adsorb on fiber paper is detected by HPLC. The concentration of Ca2+ adsorb on fiber paper is detected by AAS.

 

Sequence of Research Activities

  1. Literature survey
  2. Checking for the exist equipment and ordering for additional chemical and apparatus
  3. Setup the experiment
  4. Running the experiment
  5. Data analysis
  6. Making the project conclusion
  7. Write the complete report and paper

 

Time Table

year : 1999

 

Budget

Chemicals Total

Sodium Dodecyl Sulphate (SDS) 9,000.00

Sodium Octanoate (C8) 9,000.00

Office paper (Xerox 4200 DP 20lb.) 2,000.00

CaCl2 1,000.00

NaOH 1,000.00

Methanol 1,000.00

 

Equipment Total

Filter Paper 3,000.00

Equipment fee at Ministry of science 4,000.00

Total 26,000.00