New Carbon-Borate Nanocomposites Strip Toxic Dye from Water

A team of researchers in Saudi Arabia has developed a family of multiphase nanocomposites that can pull one of the most stubborn textile dyes out of contaminated water with remarkable efficiency. Writing in the Journal of the Saudi Chemical Society, Nada S. Al-Kadhi of Princess Nourah bint Abdulrahman University, Ehab A. Abdelrahman of Imam Mohammad Ibn Saud Islamic University, and Saad A. Aljlil of King Abdulaziz City for Science and Technology describe two novel hybrid materials that remove up to 96 percent of Victoria Blue B dye from aqueous solutions, achieving adsorption capacities that outperform many previously reported adsorbents by a wide margin.

Victoria Blue B is a cationic dye used extensively in textile, leather, and printing industries, and it presents a serious environmental challenge. Even trace quantities below one milligram per liter can impart intense coloration to water, blocking light penetration and suppressing photosynthesis in aquatic plants. The dye resists degradation by heat, light, and microbial activity, allowing it to persist and accumulate in natural water bodies. Prolonged exposure has been linked to skin allergies, respiratory irritation, gastrointestinal disturbances, and mutagenic and cytotoxic effects, making its removal from wastewater a priority for both public health and the United Nations Sustainable Development Goal 6 on clean water and sanitation.

Conventional treatment options each carry significant drawbacks. Membrane filtration is effective but expensive and prone to fouling, coagulation and flocculation generate large volumes of chemical sludge, electrodialysis demands high energy input, photocatalytic degradation often requires ultraviolet light and catalysts that lose activity over time, and bioremediation is hampered by the toxicity of the dyes themselves, which inhibit microbial growth. Adsorption has long been viewed as the most practical alternative, offering high efficiency, operational simplicity, and the possibility of regenerating and reusing the adsorbent, but the performance of the material doing the adsorbing is the decisive factor.

The novelty of the new work lies in the deliberate construction of a cooperative surface in which carbon, metal borates, and metal oxides coexist within a single hybrid architecture. The researchers synthesized two materials using the Pechini sol-gel route, a polymeric complexation method in which tartaric acid chelates magnesium, strontium, and lead ions while its hydroxyl groups form boron-tartrate complexes with boric acid through B-O linkages. Polyethylene glycol 400 acts as a polymerizing agent, creating an extended organic network that locks the metal complexes into molecular-scale uniformity. When the dried gel is calcined, the organic matrix decomposes to yield intimately mixed inorganic phases, and depending on the temperature, a portion of the carbonaceous material is retained.

Calcination at 500 degrees Celsius produced a material designated MSPB500, composed of MgSrB2O5, PbB2O4, and SrB2O4 phases embedded in a carbon-rich matrix, while treatment at 700 degrees Celsius yielded MSPB700, containing additional SrPbO3, Pb3O4, and Mg2B2O5 phases with far less carbon. X-ray diffraction confirmed the targeted phase assemblages and gave mean crystallite sizes of 57.89 nanometers for MSPB500 and 74.47 nanometers for MSPB700. High-resolution transmission electron microscopy revealed sheet-like and flake-like features for MSPB500 with a mean particle size of 59.34 nanometers, compared with denser spherical and oval aggregates averaging 160.72 nanometers for MSPB700. Energy-dispersive X-ray spectroscopy confirmed the presence of carbon, boron, magnesium, oxygen, strontium, and lead, with carbon contents of 18.5 weight percent for MSPB500 against just 4.7 percent for MSPB700.

Those structural differences translated directly into adsorption performance. MSPB500 offered a BET surface area of 6.87 square meters per gram and a total pore volume of 0.07653 cubic centimeters per gram, substantially higher than the 2.35 square meters per gram and 0.04263 cubic centimeters per gram measured for MSPB700. Under optimal conditions of pH 10 and 298 kelvin, MSPB500 achieved a maximum adsorption capacity of 369.00 milligrams per gram and a removal efficiency of 96.22 percent, reaching equilibrium within 60 minutes. MSPB700 reached a capacity of 282.49 milligrams per gram and 72.21 percent removal, equilibrating in 80 minutes. Both figures compare favorably with earlier Victoria Blue B adsorbents such as zinc oxide nanoparticles at 163.00 milligrams per gram, MCM-41 silica at 192.30 milligrams per gram, and activated carbon at 92.78 milligrams per gram.

The mechanism behind the uptake is pH-governed electrostatic attraction. The point of zero charge was measured at approximately 7.3 for MSPB500 and 8.5 for MSPB700, meaning that at pH 10 both surfaces carry a net negative charge that strongly attracts the positively charged dye molecules. Because pH 10 lies further above the point of zero charge for MSPB500, its surface is more strongly negative, which helps explain its superior performance. The borate-rich phases provide a high density of polar, non-bridging B-O oxygen sites, while the retained carbon domains contribute pi-pi interaction sites that bind the aromatic structure of the dye. Infrared spectroscopy confirmed dye loading through the appearance of characteristic C-N and aromatic C=C bands after adsorption, and elemental analysis detected nitrogen, absent from the pristine material, on the dye-loaded surface.

Kinetic and thermodynamic analyses painted a consistent picture of predominantly physical adsorption. The data followed the pseudo-first-order model with correlation coefficients of 0.9999 for both materials, and equilibrium fit the Langmuir isotherm, indicating monolayer uptake on energetically uniform sites. Adsorption was exothermic and spontaneous, with removal efficiency declining as temperature rose from 298 to 328 kelvin. Importantly, inductively coupled plasma analysis of post-adsorption filtrates detected no leaching of lead, strontium, or magnesium ions, confirming that the metals are locked into stable crystalline borate and oxide phases and that treated water is not secondarily contaminated. The materials also tolerated moderate ionic strength and outperformed expectations in the presence of competing ions, although the cationic dye crystal violet competed strongly for adsorption sites.

Practical reusability was demonstrated over five consecutive adsorption-desorption cycles using hydrochloric acid as the eluting agent. Nearly complete desorption was achieved at 2 molar acid concentration, and after five cycles MSPB500 still removed 86.64 percent of the dye while MSPB700 managed 59.79 percent. X-ray diffraction of the regenerated MSPB500 showed no significant changes in peak positions or intensities, indicating that the crystalline structure survived repeated regeneration. The team also tested the materials on real laboratory wastewater from Imam Mohammad Ibn Saud Islamic University, spiked with Victoria Blue B to 250 milligrams per liter. Despite a complex ionic background including sodium, potassium, calcium, magnesium, chloride, sulfate, bicarbonate, nitrate, and phosphate, MSPB500 still achieved a capacity of 341.85 milligrams per gram and MSPB700 reached 259.62 milligrams per gram, only modestly below their deionized-water performance.

The researchers argue that the key innovation is not any single component but the synergy created when multiple borate and oxide phases operate in parallel with carbon-derived adsorption domains, multiplying the population of accessible active sites. They note that the Pechini route offers better control over stoichiometry, particle size, and elemental distribution than conventional solid-state, co-precipitation, combustion, or hydrothermal methods, and it requires no high-pressure equipment. Future work will evaluate the nanohybrids in additional real wastewater streams, run continuous-flow fixed-bed column tests to assess scale-up feasibility, and systematically tune thermal treatment conditions to correlate phase and textural evolution with long-term regeneration stability. If those steps succeed, the multiphase carbon-borate-oxide design could offer a robust, regenerable, and comparatively simple route to cleaner industrial effluents.

Subject of Research: Development of Pechini-derived carbon, metal borate, and metal oxide nanocomposites for adsorptive removal of Victoria Blue B dye from water

Article Title: Efficient removal of Victoria Blue B dye from water using novel nanocomposites based on carbon, metal borates, and metal oxides

Article References: Al-Kadhi, N. S., Abdelrahman, E. A., & Aljlil, S. A. (2026). Efficient removal of Victoria Blue B dye from water using novel nanocomposites based on carbon, metal borates, and metal oxides. Journal of Saudi Chemical Society, 30(4), Article 58. https://doi.org/10.1007/s44442-026-00110-9

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00110-9

Keywords: Victoria Blue B, dye removal, nanocomposites, adsorption, Pechini sol-gel, metal borates, water treatment, wastewater treatment, Langmuir isotherm, pseudo-first-order kinetics, reusability, carbon nanohybrids