What is the optimal ph for methylene blue adsorption?
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Optimal pH for Methylene Blue Adsorption
Introduction to Methylene Blue Adsorption
Methylene Blue (MB) is a common dye used in various industrial applications, and its removal from wastewater is crucial for environmental protection. Adsorption is a widely used method for removing MB from aqueous solutions, and the efficiency of this process is highly dependent on several factors, including pH.
pH-Dependent Adsorption Efficiency
Optimal pH Range
Several studies have investigated the optimal pH for the adsorption of Methylene Blue onto different adsorbents. The consensus from these studies indicates that the adsorption efficiency of MB is highly pH-dependent, with optimal pH values generally falling within a specific range. For instance, activated carbon derived from Egyptian rice hulls showed an optimal pH range between 5 and 9 for MB adsorption1. Similarly, jute fiber carbon exhibited optimal adsorption at a pH range of 5 to 107.
Specific Optimal pH Values for Different Adsorbents
Different adsorbents have been tested for their MB adsorption capabilities, each showing varying optimal pH values:
- Ephedra strobilacea Char (ESC): The optimal pH for MB removal was found to be 82.
- Ephedra strobilacea Char modified with Phosphoric Acid (ESP): The optimal pH was 62.
- Ephedra strobilacea Char modified with Zinc Chloride (ESZ): The optimal pH was 92.
- Single-Walled Carbon Nanotubes functionalized with Amine (SWCNT-NH2): The best pH for MB adsorption was 93.
- Cellulosic Olive Stones Biomass: The maximum MB uptake was achieved at a pH of 104.
- Thermo Plasma Expanded Graphite (TPEG): The optimal adsorption performance was at pH 115.
- Oil Palm Leaves (OPL): The optimal pH for MB removal was found to be 66.
- Kaolin: The optimal pH for MB adsorption was 69.
- Pineapple Leaf Powder (PLP): The adsorption was favorable at higher pH, with maximum capacity observed at pH 9.58.
Mechanisms Influencing pH-Dependent Adsorption
The pH of the solution affects the surface charge of the adsorbent and the ionization state of the dye molecules, which in turn influences the adsorption process. At higher pH levels, the adsorbent surfaces tend to acquire a more negative charge, enhancing the electrostatic attraction between the negatively charged adsorbent and the cationic MB dye molecules5. Conversely, at lower pH levels, the adsorption efficiency may decrease due to competition between hydrogen ions and MB cations for the active sites on the adsorbent4.
Conclusion
The optimal pH for Methylene Blue adsorption varies depending on the type of adsorbent used, but generally falls within the range of 5 to 11. This pH dependency is primarily due to the electrostatic interactions between the adsorbent surface and the dye molecules. Understanding the optimal pH conditions for different adsorbents can significantly enhance the efficiency of MB removal from wastewater, contributing to more effective environmental management practices.
Sources and full results
Most relevant research papers on this topic
Study of adsorption isotherms and kinetic models for Methylene Blue adsorption on activated carbon developed from Egyptian rice hull (Part II).
Methylene Blue removal efficiency on activated carbon from Egyptian rice hulls exceeds 99% at 25°C, with a pH-dependent process and optimal removal at 5-9 pH, and smaller adsorbent particles.
Highly CitedKinetics, equilibrium studies and thermodynamics of methylene blue adsorption on Ephedra strobilacea saw dust and modified using phosphoric acid and zinc chloride
Methylene blue adsorption on Ephedra strobilacea char, modified with phosphoric acid, and zinc chloride adsorbents is endothermic and spontaneous, with optimal pH values of 8, 6 and 9.
Highly CitedTaguchi L9 (34) orthogonal array study based on methylene blue removal by single-walled carbon nanotubes-amine: Adsorption optimization using the experimental design method, kinetics, equilibrium and thermodynamics
The best conditions for methylene blue removal by single-walled carbon nanotubes-amine are 20 mg/L initial concentration, 0.05 g SWCNT-NH2, pH 9, and 50°C, with spontaneous and endothermic adsorption.
Highly CitedMechanistic understanding of the adsorption and thermodynamic aspects of cationic methylene blue dye onto cellulosic olive stones biomass from wastewater
Green and black olive stones are cost-effective and promising adsorbents for cationic methylene blue dye removal from wastewater, with green olive stones being more efficient at higher concentrations and 45°C being the optimal temperature.
Rigorous JournalHighly CitedMethylene blue adsorption on thermo plasma expanded graphite in a multilayer column system.
TPEG effectively removes methylene blue from wastewater, with optimal performance at pH 11, and can be reused 5 times after a simple chemical regeneration with HCl.
Adsorption of methylene blue onto oil palm (Elaeis guineensis) leaves: Process optimization, isotherm, kinetics and thermodynamic studies
Oil palm leaves effectively remove 88.72% of methylene blue from aqueous solutions, with optimal conditions at 2.22 g/L, pH 6, initial MB concentration of 259 mg/L, and temperature of 53 °C.
Adsorption of methylene blue onto jute fiber carbon: kinetics and equilibrium studies.
Jute fiber activated carbon effectively removes methylene blue from aqueous solutions, with an optimum pH of 5-10 and a capacity of 225.64 mg/g, using intraparticle diffusion as the best model.
Highly CitedRemoval of methylene blue from aqueous solution by adsorption onto pineapple leaf powder.
Pineapple leaf powder shows potential as an economical adsorbent for removing methylene blue from aqueous solutions, with adsorption favoring higher pH and lower temperature.
Highly CitedRemoval of Methylene Blue from aqueous solutions by adsorption on Kaolin: Kinetic and equilibrium studies
Raw Algerian kaolin effectively removes Methylene Blue from aqueous solutions, making it a low-cost alternative to commercial adsorbents.
Highly CitedResponse Surface Modelling of Methylene Blue Adsorption onto Seaweed, Coconut Shell and Oak Wood Hydrochars
The best adsorbent from biowaste, brown seaweed hydrochars, effectively removes >99% of methylene blue dye from wastewater, with optimal conditions being lower initial concentration, pH 6, and 84 minutes of contact time.
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