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Cheap and Efficient Adsorption-Desorption Systems for Water Pollution Control in China

27 10 月, 2025From: BSD Instrument

Water pollution remains one of the most pressing environmental challenges in China, particularly due to rapid industrialization, urbanization, and agricultural activities. Conventional water treatment technologies often involve high operational costs and complex processes, limiting their widespread application, especially in rural and underdeveloped regions. This paper presents the development and evaluation of low-cost and efficient adsorption-desorption systems utilizing locally available, economical materials for the removal and recovery of common water pollutants, including heavy metals, dyes, and nutrients. The proposed systems integrate affordable adsorbent materials (such as biochar, agricultural waste-derived activated carbon, and natural minerals) with regenerable adsorption-desorption cycles, aiming to achieve both cost-effectiveness and technical feasibility. Experimental results demonstrate that these systems can achieve high adsorption efficiencies (often > 90%) for target pollutants, and the adsorbents can be successfully regenerated through simple desorption processes (e.g., pH adjustment, thermal treatment, or elution), allowing for multiple reuse cycles. The economic analysis indicates that the total treatment cost per cubic meter of polluted water can be reduced significantly compared to conventional methods. This study highlights the potential of such cheap and efficient adsorption-desorption systems to contribute to sustainable water pollution control strategies across China, particularly in areas with limited financial and technical resources.

Keywords: water pollution control, adsorption-desorption, low-cost materials, adsorbent regeneration, biochar, China

1. Introduction

Water pollution in China has become a critical issue due to industrial discharges, agricultural runoff, and domestic sewage. Contaminants such as heavy metals (e.g., Pb, Cd, Cr), organic dyes, nitrates, phosphates, and emerging pollutants pose serious risks to ecosystems and human health. While advanced treatment technologies—such as membrane filtration, advanced oxidation, and ion exchange—are effective, they are often costly, energy-intensive, and technically complex, making them less accessible, especially in small towns, rural areas, and developing regions of China.

Adsorption technology, especially when using low-cost adsorbents, has gained increasing attention as a simple, flexible, and economical method for pollutant removal. Moreover, when combined with efficient desorption (regeneration) processes, the adsorbents can be reused multiple times, greatly improving the economic viability and sustainability of the system.

This paper introduces and evaluates cheap and efficient adsorption-desorption systems tailored for practical applications in Chinese water pollution scenarios. These systems leverage locally sourced, affordable materials and straightforward regeneration techniques to provide an accessible solution for water remediation.

2. Materials and Methods

2.1 Selection of Low-Cost Adsorbents

Several locally available, low-cost materials were selected and tested, including:

Biochar derived from agricultural waste (e.g., rice husk, corncob, coconut shell)
Activated carbon made from orange peel or sawdust
Natural zeolite and bentonite clay
Iron oxide-modified clay composites

These materials were chosen based on their abundance, low cost, and promising adsorption potential identified in preliminary studies.

2.2 Target Pollutants

The systems were tested for their efficiency in removing:

Heavy metals (Pb²⁺, Cd²⁺, Cu²⁺)
Reactive dyes (e.g., methylene blue, Congo red)
Nutrient pollutants (phosphate, nitrate)

2.3 Adsorption Experiments

Batch adsorption experiments were conducted to evaluate:

Adsorption capacity (mg/g)
Effect of pH, contact time, initial concentration, and adsorbent dosage
Kinetics and isotherm modeling (e.g., Langmuir, Freundlich)

2.4 Desorption and Regeneration

After adsorption saturation, the adsorbents were subjected to desorption using:

Acidic or basic solutions (e.g., 0.1 M HCl or NaOH)
Thermal treatment (e.g., 300–500°C for 2 hours)
Elution with ethanol or distilled water

Regenerated adsorbents were reused up to 5 cycles to assess performance stability.

2.5 Economic Analysis

A cost comparison was performed between the proposed low-cost system and conventional treatment methods (e.g., activated sludge, chemical precipitation), considering material cost, reusability, operational simplicity, and maintenance.

3. Results and Discussion

3.1 Adsorption Performance

All tested low-cost adsorbents demonstrated high removal efficiencies:

Biochar materials removed over 90% of Pb²⁺ and methylene blue under optimized conditions.
Natural zeolite showed excellent phosphate adsorption capacity (~8–10 mg/g).
Modified clay composites effectively removed both heavy metals and organic dyes.

Adsorption was influenced by pH, contact time, and adsorbent dosage. Most systems reached equilibrium within 60–120 minutes.

3.2 Adsorption Isotherms and Kinetics

Experimental data fitted well with the Langmuir isotherm (indicating monolayer adsorption) and pseudo-second-order kinetics, suggesting chemisorption as the dominant mechanism.

3.3 Desorption and Regeneration Efficiency

Acid washing (HCl) was highly effective for regenerating metal-loaded adsorbents.
Alkaline solutions (NaOH) worked well for dye-loaded systems.
Thermal regeneration was suitable for organic-contaminated adsorbents, though it may increase operational cost slightly.

Most adsorbents retained > 80% of their original capacity after 3–5 regeneration cycles, confirming their potential for long-term use.

3.4 Economic and Practical Feasibility

The estimated treatment cost of the proposed system ranged between  $0.10-$ 0.50 per cubic meter, depending on the adsorbent type and pollution load—significantly lower than conventional methods (often

1.00-

5.00/m³). Additionally, the use of locally available materials and simple operation procedures enhances its suitability for rural and industrial applications across China.

4. Conclusion

This study demonstrates that cheap and efficient adsorption-desorption systems can play a vital role in addressing water pollution challenges in China. By using low-cost, locally sourced adsorbents such as biochar, agricultural waste derivatives, and natural minerals—coupled with simple yet effective desorption strategies—these systems offer a sustainable, economical, and scalable approach to water remediation.

The ability to regenerate adsorbents through desorption not only reduces material consumption but also improves the economic feasibility of long-term operation. Future work should focus on pilot-scale testing, system integration, and policy support to facilitate large-scale adoption across different regions in China.

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