Title of the Invention:
Glass Ceramics Derived from Solid Wastes by Heavy Metal Solidification
Field of the Invention:
The present invention pertains to the fields of environmental engineering, materials
science, and industrial recycling. More specifically, it relates to the immobilization of
10 heavy metals from industrial solid wastes through the formation of durable glass ceramics
using melting, quenching, and heat treatment processes.
Background of the Invention:
Industrial activities generate large volumes of hazardous solid wastes such as fly ash, red
mud, blast furnace slag, and electronic waste residues, which contain �toxic heavy metals
15 like lead, cadmium, chromium, and arsenic. Improper disposal often leads to groundwater
contamination due to leaching. Conventional treatments are either expensive or inefficient
in long-term stabilization. Thus, there is a pressing need for a cost-effective, scalable, and
sustainable method to neutralize these hazardous elements.
Summary of the Invention:
20 The present invention provides an innovative and environmentally friendly process to
recycle industrial solid waste containing heavy metals by converting them into glass
ceramics. The process comprises grinding, mixing with additives, melting at high
temperatures ( 1200-1500�C), rapid cooling (quenching), and controlled heat treatment to
induce crystallization. The resulting glass ceramics trap heavy metals within stable
25 crystalline matrices, signfficantly reducing their leachability and environmental threat.
Detailed Description of the Invention:
Industrial processes produce significant amounts of hazardous solid wastes, including fly
ash from coal combustion, red mud from aluminum refining, blast furnace slag from steel
manufacturing, and residues from electronic waste recycling. These waste materials often
30 contain toxic heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), and arsenic
(As), which pose serious environmental and health risks. If these wastes are not properly
managed, toxic metals can leach into surrounding soils and groundwater, contaminating
water sources and threatening ecosystems and human health.
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Groundwater contamination caused by the leaching of heavy metals is. particularly
concerning due to its persistence and potential to enter the food chain. Heavy metals are
non-biodegradable and tend to accumulate in living organisms, leading to chronic
toxicity, neurological disorders, and carcinogenic effects. The challenge lies in effectively
immobilizing or removing these toxic elements from industrial wastes before disposal or
reuse .
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Traditional treatment methods such as chemical stabilization, solidification, and
landfilling have limitations. Chemical stabilization often involves expensive reagents and
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may not provide long-term containment, as changes in environmental conditions can
remobilize metals. Solidification can reduce leachability but usually involves the use of
cementitious materials, which increase the volume and cost of waste management.
45 Landfilling, on the other hand, risks environmental pollution if liners fail or leachate
treatment is inadequate.
Given these constraints, there is an urgent need for innovative approaches that are costeffective,
environmentally sustainable, and suitable for large-scale application. Emerging
methods focus on using industrial byproducts or natural materials as adsorbents or
50 stabilizers to capture heavy metals. Techniques such as hiochar amendment, geopolymers,
and microbial remediation show promise in reducing metal mobility while minimizing
environmental impact.
As a result, developing scalable and sustainable technologies to neutralize hazardous
heavy metals in industrial solid wastes is critical to safeguarding groundwater quality,
55 protecting public health, and promoting circular economy principles through safe waste
reuse.
The present invention introduces a novel and eco-friendly method for recycling industrial
solid wastes laden with heavy metals by transforming them into durable glass ceramics.
This innovative process begins with grinding the hazardous waste materials into fine
60 particles, which are then thoroughly mixed with specific additives to enhance the final
product's stability and performance. The blended mixture undergoes melting at high
temperatures ranging between 1200�C and l500�C, ensuring complete homogenization
and breakdown of harmful components.
Following melting, the molten material is rapidly cooled through a quenching process to
65 form an amorphous glass. This rapid cooling prevents the formation of unwanted
crystalline phases and prepares the material for subsequent controlled heat treatment. The
heat treatment step is carefully designed to induce crystallization, resulting in glass
ceramics with a unique microstructure that effectively immobilizes heavy metals .
By trapping toxic elements such as lead, cadmium, chromium, and arsenic within stable
70 crystalline matrices, the produced glass ceramics exhibit significantly reduced
leachability. This stabilization minimizes the risk of heavy metal release into the
environment, making the waste safe for disposal or potential reuse. The process not only
addresses hazardous waste management challenges but also promotes sustainable
recycling practices by converting harmful residues into valuable, environmentally benign
75 materials.
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80 References (Prior Art):
I. [US Patent 5,458,634)- Method for converting hazardous waste into glass.
2. [EP 1045754 AI)- Immobilization of toxic metals in glass matrices.
3. [Journal of Hazardous Materials, 2021)- Utilization of fly ash and slag in glass
ceramic production.
85 4. [Waste Management, Elsevier, 2020)- Recycling electronic waste through
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vitrification.
5. [Indian Patent IN202041 012345)- Heat treatment of glass waste for heavy
metal fixation.
Description of Figure:
The production of glass-ceramics from industrial solid waste involves a systematic multistep
process designed to ensure both performance and environmental safety. Initially, the
waste is collected, dried, and ground to a fine particle size of less than I 00 Jlm. In the raw
material mixing stage, 50-90 wt.% of this waste is combined with 10-30 wt.% silica, 5-
20 wt.% alumina, and fluxing agents such as CaO and Na,O. To enhance crystallization,
1-5 wt.% of nucleating agents like TiO, or ZrO, may also be added. This mixture is then
melted at high temperatures ranging from 1200-1500�C to form a homogeneous melt.
The molten mixture is rapidly quenched to produce an amorphous glass, which is
subsequently subjected to a controlled heat treatment at 600-900�C for I to 4 hours to
induce crystallization and form the glass-ceramic structure. Finally, the material is shaped
into useful forms such as tiles, bricks, panels, or slabs. The resulting glass-ceramics
exhibit high mechanical strength, typically exceeding 50 MPa, and comply with
environmental standards, with heavy metal leachability falling within the safe limits
defined by the EPA's Toxicity Characteristic Leaching Procedure (TCLP) .
Advantages of the Invention:
� Immobilization of heavy metals
� Converts hazardous waste to value-added products
� High mechanical strength and durability
� Eco-friendly and economically scalable
Applications:
� Construction: Tiles, bricks, decorative panels
� Radiation shielding: Dense glass ceramics
� Decorative and structural components in buildings

Claims:
l. We claim that A method for immobilizing heavy metals in industrial solid
waste comprising the steps of:
a. drying and grinding the waste;
120 b. mixing with silica, alumina, and fluxes;
c. melting at 1200-1500�C to form a homogeneous melt;
d. quenching the melt to form glass; and
e. heat treating the glass at 600-900�C for 1-4 hours to form a crystallized glass
ceramic.
125 2. We claim the method as claimed in claim I, wherein the industrial solid waste
comprises fly ash, red mud, slag, or electronic waste residues.
3. We claim the method as claimed in claim I, wherein the fluxes comprise CaO
and Na20.
4. We claim the method as claimed in claim l, wherein nucleating agents such as
130 Ti02 or Zr02 are used in l-5 wt.% to control crystallization.
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5. We claim a glass ceramic product produced by the method in claim l, having a
compressive strength of at least 50 MPa and heavy metal leachability within
EPA TCLP limits.
6. We claim the Use of the glass ceramic product claimed in claim 5 for
construction, radiation shielding, or decorative applications.0