Stabilization 1

7/27/2019 Stabilization 1

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L/O/G/O

253747 HAZARD WASTE MAN

STABILIZATION

AND SOLIDIFICATION

For Asso. Prof. Dr. Kajornsak Sopajaree

ByMiss Natthawadee Chantrawichaikun 550631031

Miss Ritthipond Laitun 550631042


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www.themegallery.com

INTRODUCTION


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The technologiesare being

applied to

the remediation of hazardouswastes sites

the treatment of

contaminated land where

large quantities of soil

containing contaminants

are encountered

the treatment of residue

from other treatment

process

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Stabilization and solidification have been widely

applied in the management of hazardous wastes.


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In general terms, stabilization is a process

where additives are mixed with waste to

minimize the rate of contaminant migration

from the waste and to reduce the toxicity of the

waste

A process employing additives by which the

physical nature of the waste (as measured by

the engineering properties of strength,

compressibility, and/or permeability) is

altered during the process.

STABILIZATION

SOLIDIFICATION


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DEFINITIONS

STABILIZATION

To minimize the rate ofcontaminant migration intoenvironment

To reduce the level of toxicity


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DEFINITIONS

FIXATION

Improve the handling and physicalcharacteristics of the waste

Decrease the surface area across whichtransfer or loss of contaminants can occur

Limit the solubility of any pollutants containedin the waste

Reduce the toxicity of the contaminants


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DEFINITIONS

Text in here

Increase the strength Decrease the compressibility Decrease the permeability of thewaste

SOLIDIFICATION


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The potential for contaminant loss from a stabilized

mass is usually determined by leaching tests. Leaching is the

process by which contaminants are transferred from a

stabilized matrix to a liquid medium such as water.

During stabilization, certain contaminants may be

destroyed such as by the dechlorination of chlorinate

hydrocarbons. Other organics may disappear as a result ofvolatilization. However, the stabilization of inorganic

contaminants that are already in their atomic form such as

cadmium, lead, and other metals should mimic nature.

DEFINITIONS


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Stabilization must be considered as a waste treatment

process that reduces, to an acceptable or geologically slow

rate, the movement of contaminants into environment.

DEFINITIONS


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It has been recognized that the disposal of liquid wastesin landfills is an environmentally unsound practice. Liquids

migrate downward through the landfill, assist in the generation

of leachate, and potentially migrate through defects in the liner

system. As a consequence of the high mobility of liquid

hazardous wastes, their disposal in landfills had been

prohibited in the US. This ban has resulted in the increased use

of stabilization in order to preclude disposal of liquid wastes. In

this application, the stabilization agents must chemically bond

the hazardous chemical in liquid wastes. The agents cannot actsimply as absorbents (physically containing the liquids much the

same way in which a sponge holds water).

REGULATIONS


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APPLICATIONS

Siteremediation

Landdisposal

Solidification

of industrialwastes


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The land disposal of liquid waste increases thelikelihood of contaminant migration (and is currently banned

under U.S. regulations.). Liquid waste, along with wet sludges,

must be stabilized prior to landfilling. To effectively stabilizedliquids, the stabilization agents cannot be absorbents (such as

sawdust). The liquids absorbed by agents could be easily

released (desorbed) in the landfill when compressed under

additional loads. That is, as more material is landfilled, the

weight of the overlying material would squeeze the liquids out

of the underlying material. Therefore, the liquids must bechemically and physically bound by the stabilization reagents

so that they are not expelled by the consolidation stress or

leached out by the downward percolation of precipitation.

LAND DISPOSAL


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The remediation of contaminated sites having organicwastes, inorganic wastes, and/or contaminated soils may be

accomplished employing stabilization technology. For site

remediation, stabilization is used to 1. improve the handling

and physical characteristics of the wastes, 2. decrease the rate

of contaminant migration by decreasing the surface area across

which the transfer of pollutants can occur and by limiting the

solubility of pollutants, and 3. reduce the toxicity of certain

contaminants.

SITE REMEDIATION


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Stabilization is particularly well suited for sites wherethe hazard involves large quantities of soils contaminated at

low levels. In many instances it may not be environmentally

sound nor cost-effective to excavate, transport, and landfill or

incinerate soils contaminated with low levels of pollutants

because of 1. the additional air pollution caused by excavation

equipment, trucks, and the exposure of buried contaminated

soils to the air, which enhances the volatilization of organics;

and 2. the increased risks as a result of traffic accidents.

SITE REMEDIATION


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Solidification (affecting of physical properties such as

strength and compressibility) improves the engineering

properties and may reduce the rate at which contaminants

migrate into the environment. Although many of the hazardous

waste materials may not endanger the public health or the

environment, the materials are frequently structurally unstable,

aesthetically unsuitable, and their condition precludes other

uses of the sites area. Thus, the primary goal of solidification is

the improvement of the structural integrity of the material.

SOLIDIFICATION OF INDUSTRIAL

WASTE


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PRECIPITATIONDETOXIFICATION

MACROENCAPSULATION

MICROENCAPSULATION

ABSORPTIONADSORPTION

MECHANISMS


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MECHANISMS

MACROENCAPSULATION MICROENCAPSULATION

Macroencapsulation is themechanism by which hazardouswaste constituents are physicallyentrapped in a larger structural

matrix, that is, the hazardous waste

constituents are held indiscontinuous pores within the

stabilizing materials. Upon physicaldegradation (breakdown) of the

stabilized material, even to relativelylarge particle sizes, the entrappedmaterials are free to migrate. Thestabilized mass may breakdown

over time (as measured on ageologic time scale) due to imposed

environmental stress. Thesestresses include such thing asrepeated cycles of wetting anddrying or freezing or thawing,

introduction of percolating fluids,and physical loading stresses.

In microencapsulation, hazardous

waste constituents are entrapped

within the crystalline structure of the

solidified matrix at a microscopic

level. As a result, even if the

stabilized materials degrade into

relatively small particle sizes, most

of the stabilized hazardous wastes

remains entrapped. However, as

with macroencapsulation, because

the waste is not chemically alteredor bound, the rates of contaminant

release from the stabilized mass

may increase as the particle size

decreases and more surface area is

exposed.


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MACROENCAP

SULATION

MICROENCAP

SULATION

This gives rise to agreater degree of

macroencapsulation inthe laboratory (a

greater number ofparticles to be

encapsulated) than inthe field (fewer, but

larger, particles to beencapsulated)


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Absorption is the process by which contaminants are taken into the

sorbent in very much the same way a sponge takes on water. As

applied in stabilization, absorption requires the addition of solid

material (sorbent) to soak up orabsorb the free liquids in the waste.The process is primarily employed to remove free liquid to improve

the waste-handling characteristics, that is, to solidify the waste. The

liquids are free to squeeze out of the material should the mass be

subjected to consolidating stresses.

ABSORPTION


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THE MOST COMMON ABSORBENT

Soil

Fly ash

Cement Kiln dust

Lime Kiln dust

Clay minerals including bentonite,

kaolinite, vermiculite, and zeolite Sawdust

Hay and straw


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In addition to the physical entrapment within the stabilized and

solidified mass described above, electrochemical interactions may

occur. Adsorption is the phenomena by which contaminants are

electrochemically boned to stabilizing agents within the matrix.

These are typically considered surface phenomena and the nature

of the bonding may be through van derWaals or hydrogen bonding.

Contaminants that are chemically adsorbed (fixed) within the

stabilized matrix are less likely to be release into the environment

than those that are not fixed. Unlike microencapsulation and

macroencapsulation, where simple particle breakdown mayenhance the rate of contaminant migration, additional

physicochemical stress is necessary to desorb the material from

their adsorbing surfaces.

ADSORPTION


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The stabilization of organic wastes using organically modified clays

illustrates how adsorption can be used in waste stabilization. Organically

modified clays are clays which have been altered by replacing exchangeable

inorganic cations adsorbed on the clay surfaces with long- chain organic cations,

rendering the clays organophilic. Organophilic clays have an affinity for organic

molecules. Without modification, naturally occurring clays are generally

organophobic.

ADSORPTION


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ADSORPTIONOrganic waste molecules are than adsorbed to the clay as

show in Fig. 1. The adsorption bond strength must then beovercome if the organic waste molecules were to be released to

migrate into the environment.

FIGURE 1 Organic waste adsorbed toan organophilic clay


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Certain stabilization processes will precipitate contaminants from the

waste resulting in a more stable form of the constituents within the

waste. Precipitates such as hydroxides, sulfides, silicates,

carbonates, and phosphates are than contained within the stabilized

mass as part of the material structure. This phenomenon isapplicable to the stabilization of inorganic wastes such as metal

hydroxide sludges.

For example, metal carbonates are typically less soluble than

metal hydroxides. At high pH, the reaction to form a metal carbonate from

a metal hydroxides sludge, is as follow:

Me(OH)2 + H2CO3 MeCO3(s) + 2H2O

Where Me represents a metallic cation

PRECIPITATION


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Certain chemical reactions taking place during the stabilization

process may result in a waste with reduced toxicity. Detoxification is

any mechanism that changes a chemical constituent into another

constituent (or form of the same constituent) that is either less ornon-toxic.

DETOXIFICATION


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TECHNOLOGY

Compartmentalized by types of additive Binder>> to strength gain with stabilization

Sorbent >> to retaining contaminants in the

stabilized matrix


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TECHNOLOGY

Application of Table 11-2 depends on Concentration of contaminant

Quantity of reagent

Synergistic effects of multiplecontaminants and reagents


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CEMENT

Principal reagent portland cement

Portland cement made by Firing a mixture of limestone and clay (or

other silicate) in kiln at high Temp.


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Cement-based stabilization

Mixed

Hydration

Wastes materials + cement

crystalline structure

consist of calcium alumino silicate

Adding water

CEMENT


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Cement-based stabilization is best suited forinorganic waste especially for heavy metals

High pH of cement, metals are retained in

insolubility hydroxide / carbonate salt Hg is predominantly held by Physical

Microencapsulation

CEMENT


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Organic contaminants interfere with thehydration process >> reduce strength,not easily

to stabilized

To reduce organic contaminants interfere with

the hydration and enhance stabilization

Natural clays

Vermiculite

Soluble sodium silicate Stabilization with cement utilization for fixing

inorganic waste

CEMENT


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Technology of cement is well known

Materials costs are relatively low

Equipment and personnel readily available

Extensive dewatering of wet sludge4

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Advantages

CEMENT


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Advantages

Process with sufficient water

Alkalinity of cement can neutralize acid waste

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CEMENT


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Sensitive of cement to the presence of

certain contaminants that could retard or

prohibit proper hydration and the resulting

setting and hardening of the material

Disadvantages

CEMENT


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POZZOLAND

Pozzoland can be react with lime andwater to produce a cementitious material

Pozzolanicconcrete

Fly ash

ground

Furnance

slag

Cement kilndust


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POZZOLAND

Stabilized materials Soil like consistency

Slow leaching

Unburned carbon in fly ash may adsorborganic from waste


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POZZOLAND

Application For organic and inorganic materials

Heavy metals


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LIME

Calcium hydroxide Ca(OH)2

Added to raise the pH of acidity sludges

with other reagents to provide the main

stabilization reaction Fly ash stabilization


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SOLUBLE SILICATE

Metals stabilization Silica reagents are acidified to form a

Monosilic Acid solution to which metal-bearing

wastes are added Combination of liquid soluble silicate and

cement


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ORGANICALLY MODIFIED CLAYS

Accomplished through the replacement ofinorganic cation within clay crystalline

mineralogical structure with organic cation

(Quaternary Ammonium ions) Additional agents are added to provide

shear strength and solidify


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MODIFIED LIME

For stabilization of organic waste Convert toxic organic wastes to an inert mass

The process employs a calcium oxide-based

reagent modified with stearic acid Heat and water-as-steam are giving off

during reaction

Wastes is converted to a dry water repellentquite strong, relatively impermeable to water


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Thermosetting Organic Polymer

Stabilized through an organic polymerprocess that involves mixing of a monomer

such as UF acts as a catalyst to form

polymer materials a sponge-like trappingsolid particles of HZW within the matrix

Final waste product often dried and

container prior to ultimate disposal


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Thermosetting Organic Polymer

Advantages General result are low density

Small quantities of additives are required to

solidify waste Most application in

solidification of liquid

Non-volatile Organic HZW


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Thermoplastic materials

Blending molten thermoplastic materialswith waste at high Temp.

When cooled typically containerized for

ultimate disposal Attention for mixed waste

Waste that is both hazardous and radioactive

The waste stabilized is no longerconsidered hazardous


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Limitation The presence of organic chemicals that act as

solvent to the stabilizing thermoplastic

materials

Thermoplastic materials


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VITRIFICATION

Melting and fusion of materials at 1600C Rapid cooling >>> non- crystalline, amorphous form

Both an in situ technique and an in plant technique

Waste more structurally stable with a reduced

potential for contaminant migration into

environmental


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In Situ Vitrification

Stabilization 1

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