Sustainable Carboxylated Cellulose Hydrogel Beads for Pb(II) Wastewater Treatment

Transcript

Hi, my name is Caesar, and I developed CLEAR beads, a carboxylated cellulose hydrogel designed to remove lead from contaminated water.

Lead pollution remains a serious threat to both human health and the environment, yet many current treatment methods are either inefficient or unsustainable. In my project, I demonstrated that CLEAR beads can remove lead in under 40 minutes, achieving adsorption capacities that outperform existing technologies. This performance is driven by a synergistic interaction between the material’s components, nearly doubling its effectiveness.

CLEAR beads are also reusable up to 8 cycles and show strong potential for real-world application due to their low cost, durability, and scalability.

What makes this material especially promising is its sustainable design. By using a deep eutectic solvent and renewable biopolymers, CLEAR beads are biodegradable, non-toxic, and produce minimal waste.

Overall, I developed a solution that is not only effective but also sustainable and scalable. I look forward to advancing CLEAR beads as a next-generation technology by testing other heavy metals, performing pilot tests in real wastewater and column systems, and patent my work. Thank you for watching!

Problem

Lead (Pb), typically present as Pb²⁺ in water, is one of the most toxic heavy metals to both the environment and human health. According to the World Health Organization, lead exposure contributes to over 1.5 million deaths annually and is linked to many chronic diseases (WHO, 2024; Figure 1). It also bioaccumulates in aquatic organisms and can persist in water bodies for centuries (Figure 2). Major sources of lead pollution include battery manufacturing, mining, and untreated wastewater from sewage plants. Existing treatment methods often face limitations such as high costs, toxic waste after use, and poor removal efficiency (Figure 3). As industrialization grows and lead poisoning rises among younger populations, there is an urgent need to develop scalable technologies that effectively remove lead while leaving a minimal environmental footprint (WHO, 2024; Shofia, 2025).

Solution

In this project, a novel technology called CeLlulosE oxAlate hydRogel (CLEAR) Beads was developed that takes advantage of a special mixture called a Deep Eutectic Solvent (DES) and renewable substrates from plant fibres and algae to create a cellulose-based ion exchange hydrogel material that has the potential of being:

Fast in removing lead at high capacities

Easy to synthesize

Biodegradable

Low cost

Non-toxic

Regenerable

Physically durable

Highly scalable

Application

CLEAR Beads can be used in industrial pretreatment systems, such as fixed-bed adsorption columns, as an intermediate treatment step for lead-contaminated effluent. This targets the removal of lead at its source and poses an effective solution for lead wastewater treatment.

Synthesis and Optimization

Figure 4 illustrates the synthesis of CLEAR beads. Cellulose microfibres were esterified with oxalate groups using a carboxylic acid DES, then sonicated with alginate to form a uniform slurry. The slurry was dropped into a calcium solution, producing ~2 mm CLEAR beads with a porous hydrogel network containing functionalized cellulose fibres.

Cellulose esterification produces the Cellulose Oxalate (COX) component. Its synthesis was optimized using a Response Surface Methodology (RSM) model to maximize carboxyl content, and the predicted optimum was successfully confirmed experimentally using titration and FT-IR (Figure 5).

Sustainable Feedstock Potential

To support a circular economy, wheat straw was tested as an alternative cellulose source. Cellulose was extracted (Figure 6), characterized by SEM, FT-IR, and microscopy, then converted into COX and titrated. Results were compared with analytical-grade cellulose.

Fundamental Performance

COX, the key lead-removal component of CLEAR beads, was tested separately using batch and column studies. Models were fitted to determine removal capacity, kinetics, and mechanism (Figure 7).

Pseudo First Order (PFO) kinetic model:

Pseudo Second Order (PSO) kinetic model:

Langmuir isotherm model:

Freundlich isotherm model:

Thomas column model:

Yoon-Nelson column model:

Bohart-Adams column model:

Yan et. al. column model:

Full Material Performance

CLEAR beads were evaluated for lead removal using a batch study. Performance parameters were extracted through modeling (same kinetic models as Fundamental Performance), followed by regeneration tests to assess reusability (Figure 6).

The lead removal capacity of the alginate component was also evaluated through a batch study to assess potential synergistic effects.

Characterization

CLEAR beads were characterized for morphology and chemistry using microscopy and FT-IR. Agitation tests tested durability by introducing CLEAR beads to vortexing at 500 rpm to see deformation resistance.

Environmental and Economic Analysis

Production cost, atom economy, and E-factor were calculated to assess sustainability. Scale-up simulations evaluated scale-up potential (Figure 8).

Sustainable Feedstock Potential Results (Figure 9.)

Cellulose extracted from wheat straw showed strong similarity to analytical-grade cellulose. Microscopy and SEM revealed comparable fibre structure and surface morphology, while FT-IR spectra were nearly identical, indicating a similar chemical profile. COX synthesized from wheat cellulose achieved the same carboxyl content, demonstrating equal functionalization potential. Minor discoloration suggested some remaining impurities.

Fundamental Performance Results (Figure 10.)

In batch studies, COX kinetics were best described by both PFO and PSO models, indicating combined physical and chemical lead removal. COX reached equilibrium in only 15 minutes with a capacity of 61.84 mg/g, showing very rapid uptake. Isotherm data fit the Langmuir model, suggesting uniform binding sites. All models accurately predicted capacity.

In column studies, COX performance was best described by the Yoon-Nelson model at both 3 cm and 6 cm bed heights. Capacity decreased under flow conditions, as expected, but removal remained fast, with breakthrough occurring in 28–51 minutes and 50% exhaustion reached in 55–126 minutes. This is scalable behaviour.

Full Material Performance Results (Figure 11.)

CLEAR beads achieved a lead removal capacity of 125.56 mg/g with equilibrium reached in 40 minutes. Kinetics followed the PSO model, indicating stronger chemical interactions. The removal capacity of the alginate hydrogel itself was 74.70 mg/g which is higher than COX but significantly slower to reach (>60 minutes). Based on the 1:1 composition, CLEAR beads showed a 1.84× synergistic increase in capacity over the expected additive value of the individual capacities of COX and alginate (68.27 mg/g vs 125.56 mg/g). CLEAR beads also removed 100% of lead from a 90 mg/L solution in under 25 minutes in a batch test that illustrated removal efficacy.

In the regeneration study, CLEAR beads maintained high removal percentages up to 7 regeneration cycles, indicating it can be reused without significant drop in performance for 8 cycles. The regeneration method of using HCl as a high-affinity solvent effectively removed the lead ions from the CLEAR beads, allowing for effective regeneration. CLEAR beads had no observable deformation or degradation after 7 regeneration cycles, further supporting CLEAR beads' reusability.

Characterization Results (Figure 12.)

Optical microscopy images showed that CLEAR beads are ~2 mm in diameter and have an evenly distributed network of alginate hydrogel and COX. FT-IR spectra of CLEAR beads and their components (COX and alginate) are consistent with literature-reported spectra, confirming successful synthesis. Agitation tests showed that CLEAR beads have significant deformation resistance, where no visible deformation is noticed on beads that were vortexed for over 24 hours.

Environmental and Economic Analysis Results (Figure 13.)

CLEAR beads cost only $0.02 per gram to produce. The synthesis showed high atom economy (92.9%) and low waste generation (E-factor 6.04), indicating strong alignment with green chemistry principles. Scale-up simulations also produced promising parameters for future scale-up potential. One simulation is shown in Figure 13.

CLEAR Beads Support a Circular Economy

Wheat cellulose shows strong potential as a renewable feedstock for the COX component of CLEAR beads. As Canada is a major wheat producer, agricultural residues can be effectively converted into treatment materials. Further refinement of the extraction process is needed to reduce impurities.

COX show Strong Lead Removal

COX removes lead rapidly, faster than many conventional adsorbents such as activated carbon. Its capacity was competitive with similar technologies, while modelling indicated efficient removal behaviour.

COX maintained rapid removal in column studies with expected reduction in capacity seen in dynamic systems. Breakthrough modelling suggested predictable behaviour and scale-up potential.

CLEAR Beads show Synergistic Strong Lead Removal with Potential for Industrial Use

CLEAR beads reached a high capacity of 125.56 mg/g with a fast equilibrium time of 40 minutes. This exceeded the expected capacity, indicating synergistic interactions between COX and alginate.

CLEAR beads fully removed lead from highly contaminated solutions, suggesting suitability for industrial wastewater such as battery manufacturing.

CLEAR Beads are Regenerable

CLEAR beads are reusable for 8 cycles while maintaining strong performance. This improves cost-effectiveness and reduces waste compared with single-use adsorbents.

CLEAR Beads have Good Mechanical Properties

CLEAR beads showed uniform COX distribution and strong mechanical integrity. Agitation results suggest they can withstand stresses in columns.

CLEAR Beads are Low-Cost and Sustainable

CLEAR beads are inherently biodegradable and non-toxic and uses an efficient low-waste synthesis. Estimated cost is $0.02/g, lower than many technologies. Simulations also indicated favourable sustainability metrics.

Future Work: Selectivity, Pilot Testing, Patenting

While lead is the biggest environmental and health concern, future studies should test CLEAR beads on other heavy metals such as cadmium, mercury, copper, zinc, and chromium. Comparing removal performance across metals would determine the selectivity of CLEAR beads and expand their potential applications.

Although simulations and column studies showed strong scalability, further validation should be done using larger treatment columns and real wastewater containing multiple contaminants.

CLEAR beads would be a strong candidate for patenting and commercialization to help communities affected by heavy metal pollution. Further developments should provide evidence for patenting.

The student researcher gratefully thanks the Department of Chemistry and Biochemistry at the University of Windsor for providing access to faculty and undergraduate research laboratories.

Appreciation is also extended to Lauren Pandolfi for laboratory training and protocols, and to Amit Sur for fume hood access and instrumentation support.

The author would like to especially recognize the Simon Rondeau-Gagné research group for providing laboratory space, funding, resources, and a safe research environment throughout this work. Deepest gratitude is extended to Dr. Simon Rondeau-Gagné for his mentorship, encouragement, and generous support during the project. Special thanks are also given to Maxime Roger and Angela Awada for their primary supervision, consistent guidance, technical assistance, and meaningful intellectual contributions to the project design, methodology, and overall development. This work would not have been possible without their support and dedication.

The image shows the student researcher with Dr. Simon Rondeau-Gagné (left) and Maxime Roger (right).

Statistical analyses were conducted using JMP Student Edition, Microsoft Excel. Figures and graphical illustrations were created using Microsoft PowerPoint, BioRender, and Canva.

All figures, images, and data visualizations were created by the student researcher unless otherwise stated.

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