Crystal Violet: Triphenylmethane Basic Dye

Crystal violet is a classic triphenylmethane-type basic dye. Its structure is centred on a conjugated framework comprising three benzene rings and a central quaternary ammonium carbon atom; the molecule carries a positive charge and contains chloride ions as counterions, and its aqueous solution is blue-violet in colour. This substance is chemically stable and possesses good dyeing properties and antibacterial activity. It is widely used as a Gram stain for biological specimens and a histological staining reagent, and is also applied in the fields of disinfectants, acid-base indicators, textile dyeing and biological preservation.

Studies of crystal violet removal from aqueous solution

Colored water emerging from industrial activities, mainly from using dyes, is a major environmental threat. Effluents from these industrial facilities are toxic and affect human health and aquatic life. The intense color of wastewater prevents sunlight from penetrating the water, resulting in the effluent having a higher chemical oxygen demand (COD). Crystal violet (CV), chemically known as N-[4-[bis[4-dimethyl-amino)-phenyl]-methylene]-2,5-cyclohexadien-1-ylidine]-N methylmethanaminium chloride, belongs to the category of triarylmethane-based dyes. It is characterized by its alkalinity and higher toxicity than anionic dyes5. CV has emerged as a persistent dye, recognized for its extended environmental presence and consequential toxic impacts. Within the textile industry, it serves as a purple dye, whereas in paper production, it is a vital component for navy blue-black hues for inks (in writing, painting, and printing). Crystal violet exerts detrimental influences on human health, posing severe eye irritation, skin disorders, respiratory issues, kidney failure, and even cancer7. Consequently, treating wastewater containing CV is imperative before discharge into the ecosystems. The negatively charged functional groups of GO-SO3H are expected to increase the adsorption capacity via the electrostatic and dispersion interactions with the positively charged CV dye. Therefore, we sulfonated GO via reaction with diazo salt of sulfanilic acid to obtain an enhanced adsorbent for the removal CV. The performance of the novel adsorbent was evaluated through a combination of experimental and computational methods, providing insights into the adsorption mechanism. The sulfonated graphene oxide (GO-SO3H) was modeled, permitting the investigation into six different adsorption sites and the importance of the carboxylic and sulfonic groups to the interaction of GO-SO3H with the crystal violet.[1]

Expectedly, the electrostatic interaction between GO-SO3H and CV would be enhanced when pH increased because the sulfonic, carboxyl, and phenolic hydroxyl groups on GO-SO3H would deprotonate respectively, to form 𝑅−SO2−3, R-COO−, and R-O− groups, leading to a negative surface. Thus, GO-SO3H adsorption capacity for CV increased quickly with pH. Also, H+ ions would compete with CV+ for exchangeable cations on the GO-SO3H in a very acidic solution, where the sulfonic groups would protonate to create sulfonic acid. As a result, the electrostatic interactions between CV and GO-SO3H would be very weak, reducing crystal violet adsorption onto GO-SO3H and leading to a low adsorption of CV. Conclusively, pH significantly impacted CV adsorption onto GO-SO3H. We successfully synthesized sulfonated graphene oxide (GO-SO3H) and applied it for crystal violet (CV) adsorption from an aqueous solution. The results showed that GO-SO3H can effectively and adequately remove CV. Based on the effect of solution pH, CV adsorption was favored by increased pH, optimized at the pH of 8. Further, pseudo-second-order best describes the adsorption kinetic. The data fit well into Langmuir and Freundlich except at 298 K, where only Langmuir isotherm was most suitable. The increase in temperature of the aqueous solutions favored the spontaneity of CV removal. The achieved maximum adsorption capacity (202 mg‧g−1) was favored by electrostatic and dispersion interactions, confirmed by experimental and computational studies. Consequently, sulfonated graphene oxide is an excellent adsorbent for crystal violet.

New Treatment for Percutaneous Sites in Patients

Infection of the percutaneous site of a ventricular assist device (VAD) is a challenging complication. We report our experience with crystal violet Solbase (Nihon University crystal violet method) for prevention of driveline or cannula infections in VAD patients. Patients and Methods: The crystal violet method was used in 10 patients (prophylaxis in nine and treatment in one). Eight patients had an extracorporeal VAD (Nipro) and two had an implantable VAD (Heart Mate II).[2]

For disinfection of the percutaneous site, an ethanol swab was used up to postoperative day 3, after which chlorhexidine was employed. Following disinfection, the cannula or driveline site was covered with crystal violet Solbase (0.01% methylrosanilinium chloride in Solbase [macrogol 400:50 g and macrogol 4000:50 g]). The infection-free period was 4–623 days (mean: 144.2 ± 222.9 days). All eight patients with an extracorporeal VAD died, while the two patients with an implantable VAD (Heart Mate II) survived. Infection was improved in a patient with MRSA, and the results of bacteriological examination were always negative in the patients receiving prophylaxis. The two patients with an implantable VAD had no infection for 2 and 20 months after implantation. These findings suggest that the Nihon University crystal violet method is effective for prevention and treatment of driveline or cannula infections in patients with a VAD.

References

[1]Oluwasina OO, Adelodun AA, Oluwasina OO, Duarte HA, Olusegun SJ. Experimental and computational studies of crystal violet removal from aqueous solution using sulfonated graphene oxide. Sci Rep. 2024 Mar 14;14(1):6207. doi: 10.1038/s41598-024-54499-7. PMID: 38485952; PMCID: PMC10940666.

[2]Sezai A, Niino T, Osaka S, Yaoita H, Arimoto M, Hata H, Shiono M. New Treatment for Percutaneous Sites in Patients with a Ventricular Assist Device: Nihon University Crystal Violet Method. Ann Thorac Cardiovasc Surg. 2016 Aug 23;22(4):246-50. doi: 10.5761/atcs.oa.15-00250. Epub 2016 Apr 18. PMID: 27086670; PMCID: PMC5045852.