1.

Adsorption of organic water pollutants by clays and clay

minerals composites: A comprehensive review

Dina Ewis, Muneer M. Ba-Abbad, Abdelbaki Benamor, (November 2022)

Muftah H. El-Naas

This review explores the use of clays and their composites, such as bentonite,
montmorillonite, and kaolinite, in removing organic pollutants from water.

Key points from the review include:

1. Importance of Clays and Composites: Clays are inexpensive, non-toxic, and

naturally available, making them attractive for water remediation. The study
focuses on clay composites, which are clays modified with materials like
carbon, metals, and polymers to enhance their adsorption properties.
2. Challenges with Raw Clays: While raw and chemically modified clays have
been used as adsorbents, they often show low adsorption capacity and limited
ability to regenerate after use. These limitations prompted the development
of clay composites with enhanced features.
3. Clay Composites: Various clay composites, including bentonite,
montmorillonite, and kaolinite, intercalated with different materials (e.g.,
metals, metal oxides, chitosan), were evaluated. These composites have
higher adsorption capacities and are easier to recover from water, making
them more efficient than unmodified clays.
4. Adsorption Mechanism and Properties: The review covers the
physicochemical properties that influence the adsorption performance, such
as surface area, pore structure, and interaction with pollutants.
5. Research Gaps: The review highlights the need for further research,
particularly in optimizing regeneration methods, scaling up processes, and
exploring more environmentally friendly composites.

In conclusion, the study serves as a critical assessment of recent advances in the use
of clay-based composites in water treatment, offering insights into their potential
and limitations for future research.
 2. Prospect of clay-based flexible adsorbent coatings as
cleaner production technique in wastewater treatment,
challenges, and issues: A review

Syahida Farhan Azha, Mohammad Shahadat, Suzylawati Ismail, (March 2021)

Syed Wazed Ali, Shaikh Ziauddin Ahammad

The review on "Prospect of Clay-Based Flexible Adsorbent Coatings as Cleaner

Production Technique in Wastewater Treatment" discusses the promising role of
clay-based materials in water pollution control. Clays, such as bentonite and
kaolinite, possess high surface area, ion exchange capacity, and adsorption
capabilities, making them effective for removing pollutants like heavy metals, dyes,
and organic compounds from wastewater. When used as flexible coatings, clay-based
adsorbents can be applied to surfaces in treatment systems, offering a cost-effective
and environmentally friendly solution. The review highlights that these coatings have
the potential to address pollution at large scales with minimal chemical input,
contributing to sustainable water management.

Despite their advantages, several challenges hinder the practical application of clay-
based adsorbent coatings. One of the primary issues is the mechanical durability of
these coatings. They tend to experience cracking, peeling, and reduced performance
over time, especially under harsh wastewater conditions. Additionally, there are
concerns about the long-term stability of clay-based adsorbents and the difficulty in
regenerating them after multiple adsorption cycles. This limits their reusability and
economic feasibility, especially in continuous operations. Therefore, optimizing the
structure of these coatings to enhance their longevity remains a critical area of
research.

The review further emphasizes the need for advancements in the production
techniques of clay-based coatings. Improving their adsorption efficiency, durability,
and the ease of regeneration could unlock their potential in wastewater treatment.
The research community is encouraged to explore novel modifications of clay
composites with polymers, carbon materials, and metal oxides to overcome these
limitations. In doing so, these materials could become a key component in cleaner,
more sustainable production techniques for addressing global water pollution
challenges.
 3. Clay nano-adsorbent: structures, applications
and mechanism for water treatment.

Anuradha Awasthi, Pradip Jadhao, Kanchan Kumari (August 2019)

The review "Clay Nano-Adsorbent: Structures, Applications, and Mechanism for

Water Treatment" highlights the significance of clay-based nanomaterials in water
treatment processes. Key points from the review include:

1. Nanostructure of Clay Materials: Clay nano-adsorbents are characterized by

their high surface area and porosity, which enhance their ability to adsorb
pollutants. These nanomaterials can be further classified into different types
based on their matrix composition, such as metal-based, polymer-based, and
ceramic-based nanocompositesThis structural diversity allows for the
development of tailored adsorbents to target specific pollutants.
2. Applications in Water Treatment: Clay nano-adsorbents have been
successfully used for the removal of both organic and inorganic pollutants,
including heavy metals and dyes. These materials provide a cost-effective
alternative to traditional water treatment methods like reverse osmosis and
membrane filtration, which are often expensive and energy-intensive. Nano-
adsorbents are also more efficient in removing contaminants even at low
concentrations and can be regenerated for multiple uses.
3. Adsorption Mechanism: The adsorption process in these nano-adsorbents is
primarily influenced by their surface properties, including hydrophobicity and
hydrophilicity. The Langmuir and Freundlich adsorption isotherms are
commonly used to describe the adsorption behavior. These models explain
how pollutants adhere to the surface of the adsorbent in a monolayer or
multilayer fashion. The review emphasizes the potential of clay nano-
adsorbents as an environmentally friendly solution to water pollution

This review underscores the growing importance of nanotechnology in addressing

global water pollution challenges through sustainable and efficient materials.
 4. Bamboo-derived adsorbents for environmental remediation: A
review of recent progress.

Dimitrios Kalderis, Azam Seifi, Trinh Kieu

Trang Toshiki Tsubota, Ioannis Anastopoulos, Ioannis Manariotis, (May 2023)
Ioannis Pashalidis, Alireza Khaaee

The review titled "Bamboo-derived adsorbents for environmental remediation: A

review of recent progress" dives into the advancements in using bamboo-based
materials for environmental cleanup, particularly in wastewater treatment. Bamboo,
being a sustainable and cost-effective biomass, has shown great promise as an
adsorbent due to its natural porosity and carbon content, which can be enhanced
through various modification techniques.

The study highlights the versatility of bamboo-derived materials, including biochar

and activated carbon, which are capable of removing a wide range of pollutants such
as heavy metals, organic contaminants, and dyes from wastewater. These adsorbents
have a high adsorption capacity and can be modified chemically to further improve
their performance. Bamboo's rapid growth and renewability make it an attractive
option for large-scale environmental applications.

However, the review also points out several challenges that need to be addressed,
such as the consistency of material properties, scalability of production methods, and
long-term environmental impacts. The authors call for more research to optimize the
production processes and to explore the full potential of bamboo-based adsorbents
in environmental remediation.
 5. Bamboo-Based Biofoam Adsorbents for the Adsorption of
Cationic Pollutants in Wastewater: Methylene Blue and Cu(II).

Chongpeng Qiu, Chongpeng Qiu, Xuelun Zhang, You Zhang (August 2021)
Qi Tang, Zihui Yuan, Cornelis F. De Hoop, Jiwen Cao
Shilin Hao, Ting Liang, Feng Li, Xingyan Huang

The paper titled "Bamboo-Based Biofoam Adsorbents for the Adsorption of Cationic
Pollutants in Wastewater: Methylene Blue and Cu(II)" investigates the potential of
bamboo-based biofoam as a low-cost, eco-friendly adsorbent for treating
wastewater. The study focuses on the adsorption of two common cationic pollutants:
methylene blue (MB) and copper ions (Cu(II)) from aqueous solutions. Bamboo-
based biofoam presents unique characteristics such as high porosity and large
surface area, which enhance its adsorption capacity for these contaminants.

The biofoam's adsorption mechanism is primarily driven by electrostatic interactions

between the negatively charged surface of the biofoam and the positively charged
pollutants. The research highlights how bamboo biofoam can effectively remove MB
and Cu(II) from wastewater, making it a promising alternative to conventional
treatment methods. Additionally, the study provides insights into optimizing the
preparation of biofoam adsorbents to enhance their performance in practical
applications.

The findings suggest that using bamboo-derived biofoam in water treatment can be a
sustainable and scalable solution for environmental remediation. This approach
aligns with the increasing demand for green technologies in wastewater
management, offering both environmental and economic benefits.
6.Potential application and regeneration of bamboo biochar for
wastewater treatment: A review
(Odega et al., 2023)

Introduction

Bamboo biochar, produced through the pyrolysis of bamboo, has emerged as a

promising material for wastewater treatment. Its unique properties—high surface
area, porosity, and rich functional groups—enhance its ability to adsorb pollutants.

Applications in Wastewater Treatment

1.Adsorption of Contaminants:

Bamboo biochar effectively adsorbs heavy metals (e.g., Pb, Cd) and organic
pollutants (e.g., dyes, pharmaceuticals) from wastewater.

Its surface chemistry allows for high removal rates, making it suitable for various
applications.

2.Nutrient Removal:

It can also help remove nutrients like nitrogen and phosphorus, which are common
in agricultural runoff.

3.Microbial Support:

Bamboo biochar can serve as a substrate for microbial communities that degrade
organic matter and improve water quality.

Regeneration of Bamboo Biochar

1.Thermal Reactivation:

Bamboo biochar can be regenerated through thermal processes, restoring its

adsorption capacity. This is particularly effective after saturation with pollutants.

2.Chemical Treatments:

Chemical regeneration methods (e.g., using acids or bases) can enhance the surface
characteristics of biochar, allowing for repeated use.
3.Environmental Considerations:

Regeneration methods must be sustainable and not produce harmful by-products,

ensuring that the overall process remains environmentally friendly.

Results and Efficacy

Studies show that bamboo biochar can achieve over 90% removal efficiency for
certain pollutants under optimal conditions.

Regeneration techniques have demonstrated that the biochar can maintain

significant adsorption capacity even after multiple cycles of use, making it a cost-
effective solution.

Conclusion

Bamboo biochar holds significant potential for wastewater treatment due to its
adsorption capabilities and regenerative properties. Further research into optimizing
regeneration methods and understanding its long-term effects on ecosystems is
essential for its widespread application.

7.Copper modified activated bamboo charcoal to enhance

adsorption of heavy metals from industrial wastewater
(Thotagamuge et al., 2021)

Introduction

Activated bamboo charcoal has garnered attention for its effective adsorption
properties, particularly in removing heavy metals from industrial wastewater.
Modifying this charcoal with copper aims to enhance its adsorption capabilities
further.

Modification Process

Copper Ion Loading: Bamboo charcoal is treated with copper ions, typically through
impregnation techniques. This process improves the surface reactivity and increases
the availability of active sites for heavy metal binding.
Mechanism of Adsorption

1.Ion Exchange: The modified bamboo charcoal facilitates ion exchange, where
copper ions displace heavy metal ions from the wastewater.

2.Chemical Interaction: The presence of copper enhances interactions between the

charcoal surface and metal ions through complexation, leading to improved
adsorption.

Results

1.Enhanced Adsorption Capacity:

Studies indicate that copper-modified bamboo charcoal shows significantly higher

adsorption rates for heavy metals like lead (Pb), cadmium (Cd), and chromium (Cr)
compared to non-modified charcoal.

Removal efficiencies can exceed 95% for certain metals under optimal conditions.

2.Kinetics and Isotherms:

Adsorption kinetics typically follow pseudo-second-order models, indicating a

chemisorption process.

Isotherm studies suggest that Langmuir or Freundlich models can describe the
adsorption behavior, showcasing a finite number of active sites.

3.Reusability and Stability:

The modified charcoal demonstrates good reusability, maintaining a significant

portion of its adsorption capacity over multiple cycles. This is crucial for cost-
effectiveness in industrial applications.

Conclusion

Copper modification of activated bamboo charcoal markedly enhances its capacity to

adsorb heavy metals from industrial wastewater. This approach not only improves
performance but also promotes the sustainable use of bamboo charcoal as an
effective treatment option. Further research could focus on optimizing the
modification process and exploring other metal interactions for broader applications.
8. Use of biochar as a low-cost adsorbent for removal of heavy
metals from water and wastewater: A review
(Biswal & Balasubramanian, 2023)

Introduction

Biochar, a carbon-rich byproduct of biomass pyrolysis, has gained recognition as a

low-cost adsorbent for removing heavy metals from water and wastewater. Its
unique properties make it an attractive alternative to traditional treatment methods.

Properties of Biochar

High Surface Area: Provides ample sites for adsorption.

Porosity: Enhances the capacity to trap contaminants.

Functional Groups: The presence of oxygen-containing groups (e.g., carboxyl,

hydroxyl) facilitates interactions with heavy metal ions.

Mechanisms of Adsorption

Physical Adsorption: Involves Van der Waals forces and can be influenced by surface
area and pore structure.

Chemical Adsorption: Involves stronger interactions, such as ion exchange and

complexation, particularly with functional groups on the biochar surface.

Electrostatic Attraction: Oppositely charged metal ions are attracted to the

negatively charged sites on biochar.

Results and Efficacy

1.Removal Efficiency:

Numerous studies report that biochar can achieve removal efficiencies of over 90%
for heavy metals like lead (Pb), cadmium (Cd), and arsenic (As) under optimal
conditions.
2.Kinetics and Isotherms:

Adsorption kinetics typically follow pseudo-second-order models, indicating that

chemisorption plays a significant role.

Isotherm studies often fit the Langmuir or Freundlich models, showing favorable
adsorption characteristics.

3.Cost-Effectiveness:

Biochar is produced from various biomass sources, making it widely available and
low-cost.

Its production can be integrated into waste management practices, turning

agricultural residues into valuable resources.

4.Reusability:

Biochar can often be regenerated and reused multiple times, maintaining significant
adsorption capacity, which enhances its economic viability.

Conclusion

Biochar serves as a highly effective and low-cost adsorbent for the removal of heavy
metals from water and wastewater. Its use not only addresses pollution but also
contributes to sustainable waste management practices. Future research should
focus on optimizing production methods, exploring various feedstocks, and
evaluating long-term environmental impacts to maximize the benefits of biochar in
water treatment applications.
9. Synthesis of carbon fiber aerogel from natural bamboo fiber and
its application as a green high-efficiency and recyclable adsorbent
(Jiao et al., 2016)

Introduction

Carbon fiber aerogel synthesized from natural bamboo fibers presents a promising
solution for environmental remediation, particularly as an adsorbent for pollutants.

This lightweight material combines the advantageous properties of aerogels with the
sustainability of bamboo.

Synthesis Process

1.Raw Material Preparation: Natural bamboo fibers are processed to remove

impurities and enhance their uniformity.

2.Carbonization: The prepared fibers undergo pyrolysis, transforming them into

carbonaceous material at high temperatures in an inert atmosphere.

3.Activation: The carbonized bamboo fibers may be further activated to increase

surface area and porosity, enhancing their adsorption capacity.

Properties of Carbon Fiber Aerogel

1.High Surface Area: Offers extensive sites for pollutant adsorption.

2.Porosity: Lightweight structure allows for high absorption efficiency.

3.Eco-Friendly: Utilizes renewable bamboo resources, contributing to sustainability.

Applications as an Adsorbent

1.Heavy Metal Removal: The aerogel demonstrates significant effectiveness in

adsorbing heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) from
aqueous solutions.

2.Organic Pollutant Adsorption: It is also capable of adsorbing various organic

pollutants, including dyes and pharmaceuticals, making it versatile for different
wastewater types.
Results and Efficacy

1.Adsorption Capacity: Studies indicate that carbon fiber aerogel can achieve over
90% removal efficiency for targeted pollutants under optimal conditions.

2.Kinetics: Adsorption kinetics generally follow a pseudo-second-order model,

suggesting a strong chemisorption process.

3.Isotherms: The adsorption behavior aligns well with the Langmuir isotherm model,
indicating uniform adsorption sites within the aerogel.

4.Recyclability: The aerogel can be easily regenerated and reused multiple times
without significant loss in adsorption performance, enhancing its practicality for
industrial applications.

Conclusion

Carbon fiber aerogel derived from bamboo fibers is a highly effective, eco-friendly,
and recyclable adsorbent for pollutant removal. Its high efficiency in adsorbing both
heavy metals and organic contaminants positions it as a valuable material in
wastewater treatment and environmental remediation. Future research may focus
on optimizing synthesis methods and exploring broader applications in pollution
control.

10. Antibiotic adsorption by natural and modified

clay minerals as designer adsorbents for
wastewater treatment: A comprehensive review
(Hacıosmanoğlu et al., 2022)

Introduction:

The presence of antibiotics in wastewater poses significant environmental and public

health risks. Natural and modified clay minerals have emerged as effective
adsorbents for removing these contaminants. This review comprehensively examines
their adsorption capabilities, mechanisms, and modifications to enhance
performance.
Key Findings:

Types of Clay Minerals:

Natural clays (e.g., bentonite, kaolinite) possess a high surface area and cation-
exchange capacity, making them suitable for adsorption.

Modified clays (e.g., organoclays, nanoclays) show improved adsorption properties

due to enhanced surface characteristics and functional groups.

Adsorption Mechanisms:

Physical Adsorption: Involves van der Waals forces and electrostatic interactions.

Chemical Adsorption: Occurs through covalent bonding and ion exchange, often
enhanced by surface modifications.

Factors influencing adsorption include pH, temperature, contact time, and initial
antibiotic concentration.

Modification Techniques:

Organic Modification: Incorporating organic compounds to improve hydrophobicity

and enhance interactions with organic pollutants.

Inorganic Modification: Adding metal oxides or other minerals to increase surface

area and adsorption sites.

Performance Comparison:

Modified clays generally exhibit higher adsorption capacities than natural clays,
demonstrating significant improvements in removing specific antibiotics.

Studies show that the choice of clay and its modifications play a critical role in
effectiveness.

Challenges and Limitations:

Potential leaching of modified materials into water bodies.

The regeneration and reuse of adsorbents remain areas needing further research.

Scale-up processes for practical applications in wastewater treatment systems

require optimization.

Case Studies:
Various studies highlighted the effectiveness of modified clays in removing
antibiotics like tetracycline, amoxicillin, and sulfonamides from aqueous solutions.

Conclusion:

Natural and modified clay minerals represent promising materials for designing
effective adsorbents in wastewater treatment applications. Continued research into
modifications and practical applications will further enhance their capabilities,
addressing the urgent need to mitigate antibiotic pollution. Future studies should
focus on sustainability, regeneration techniques, and large-scale implementation to
optimize their use in real-world scenarios.