Among these, pseudo second order was found to be the most suitable for studying the adsorption of MB on physical activated carbon. PCC Corn cob carbon treated with peroxide NCC Corn cob carbon treated with nitric acid CCC Corn cob carbon treated with carbon dioxide SCC Corn cob carbon treated with steam.
Introduction
- Waste water
- Activated Carbon
- Biowaste material
- Corn Cobs
The quality of activated carbon depends on the surface area, porosity and surface functional groups. The presence of carbonyl, phenol, ethers was confirmed by the CO profile of CCC & SCC, which gave the maximum above 673 K. The PZC of different CC samples, shown in Table 4.2, activated by different treatments were determined using the procedure standard now. mentioned in chapter 3. 2: PZC of activated carbon CC.
Methods and Materials
Methylene Blue Dye
Vmono: Volume of the gas required to form one complete monolayer of adsorbate on the surface of the adsorbent. Vtotal: Total volume of gas adsorbed on the surface of the adsorbent at the given temperature and pressure. Temperature programmed degradation (TPD) has been used to study the surface functionality of carbons.
The Langmuir constants, Qm and KL, can be calculated from the slope and intercept of the linear graph, respectively. ΔH and ΔS can be calculated from the slope and intercept of the linear graph (negative slope) of ln Keversus 1/T, respectively. Surface area is one of the important parameters in determining the quality and efficiency of activated carbon.
Various kinetic models were studied to understand the kinetics of the adsorption of MB on activated carbon as already mentioned in chapter 3.
Preparation of carbon
Activation of Carbon
- Chemical activation
- Physical activation
Chemical activation involves treatment with acids, bases and salts in solutions which is easy to perform as it requires a lower temperature than physical activation methods. Compared to physical activation, chemical activation is preferred due to its lower temperature requirement, shorter activation time and high yield. A change in the dimensions of the precursor was observed during chemical activation, which is necessary to assimilate the reagent into the precursor, leading to the formation of a microporous structure.
The usual method of activation involves washing carbon with distilled water followed by treatment with oxidizing agent in the ratio of 50:50 (v/v. One of the advantages of physical over chemical activation is the preservation of the microstructure in the activated carbon) which is not possible in chemical activation. After reaching the required temperature, the N2 generator was switched off and CO2 gas was passed through for 2 hours at 700˚C.
After processing, the N2 generator was turned on again and the sample was allowed to cool.
BET surface area
Physical activation increases pore structure due to partial oxidation of carbon by oxidizing gases such as CO2 and steam. Since the activation of carbon via physical methods requires a very high temperature, a loss of carbon quantity is expected. Due to the high temperature requirements and the low reaction rate between the oxidizing gas and the sample, physical activation generally produces a low product yield.
N2 gas was passed through the sample until the oven temperature reached the required set value to ensure the complete absence of oxygen. For all activation processes, the N2 gas flow rate and furnace heating rate were kept constant at 100 mL/min and 10K/min, respectively. Po: Saturated vapor pressure of the gas at temperature T and p is the pressure of the gas.
C= exp where E1 is the heat of adsorption in the first layer and EL is the second and higher layers and is equal to the enthalpy of liquefaction.
TGA
TPD
PZC
The amount of dye adsorbed onto the surface of activated carbon increases with increasing contact time until a plateau is obtained. The difference in the effectiveness of these carbons proved the importance of the type of treatment for the properties of activated carbon. It was observed that physically activated carbon showed more CO2 and CO compared to raw carbon.
The parameters of Langmuir isotherm were calculated using adsorption isotherm equation as shown in Table 4.5 for chemically activated carbon and Table 4.6 for physically activated carbon. The value of RL was found to be between 0 and 1 (as shown in. Table 4.5) for this study, which confirms the favorable adsorption of methylene blue on activated carbon under experimental conditions. The value of RL was found to be between 0–1 for all adsorption studies, further confirming the favorable adsorption of MB on activated carbon.
Preparation of activated carbon from dried pods of Prosopis cineraria with zinc chloride activation for the removal of phenol.
Experimental section
Effect of contact time
It represents the state of dynamic equilibrium where the amount of dye adsorbed on the adsorbent is in equilibrium with the dye present in solution. This equilibrium was observed at about 90 minutes for physically treated carbon and 120 minutes for chemically treated carbon. The achievement of equilibrium takes a little longer due to a complex mechanism involved in the adsorption of dyes on the macro- and micropores of activated carbon.
With increasing methylene blue concentration, the amount of adsorbed dye per unit mass of carbon (absorbing unit capacity) increases while it decreases with increasing adsorbent dose due to the unsaturation of adsorption sites.
Effect of adsorbent mass
Adsorption isotherm
The RL value was found to be the determining factor for determining the type of adsorption.
Adsorption kinetics
In intraparticle diffusion model, a plot of qtversus t1/2 is drawn to check the validity of this model. The correlation coefficient values were close enough to the ideal value, but do not fit well in comparison with the pseudo second-order kinetics values. It involves the preferential movement of species from the bulk of solution to the micropores of the solid phase.
Where q is the sorption capacity at time t, Kd, Ciare the diffusion and intraparticle diffusion constants calculated from the slope and intercept, respectively. Where q is the sorption capacity at time t, β & α are the Evolich constants determined from the slope and intercept of the graph, respectively.
Determination of Thermodynamic parameters
Physically activated carbon performed better, which can be shown by 92% removal of MB by SCC and 100% by CCC, as shown in the following Table 4.3. : Equilibrium parameters qe and % adsorption of MB on chemically activated carbons. d) adsorption capacity of the unit for 10 mg/L MB conc. Pseudo-first-order kinetics parameters were calculated for chemically treated (as shown in Table 4.7) and physically treated (as shown in Table 4.8) carbon.
Pseudo second-order kinetics was found to be the best-fit model for adsorption of MB on activated carbon based on quantitative comparison made using correlation coefficient values. Preparation of activated carbon from biowaste: effect of surface functional groups on methylene blue adsorption. Adsorption properties of malachite green on activated carbon derived from rice husks produced by chemical-thermal process.
Production of granular activated carbon from fruit stones and nut shells and evaluation of their physical, chemical and adsorption properties.
Results and Discussions
Characterization
- BET
- TGA
- TPD
- PZC
The first stage is in the range of 323 to 383K with a weight loss of about 11.23%, which explains the moisture loss from the sample. The second phase can be called the main phase of decomposition, since 46.5% of the weight loss occurs within the temperature range of 383-673 K. This loss can be attributed to the decomposition of chemically bound water, cellulose, hemicelluloses and lignin.
Upon further heating at a temperature higher than 673K, 35.2% of the weight loss can be attributed to the formation of volatile products such as CO, CO2 etc. The overall process of TPD analysis can be summarized as the translation of functional groups such as carboxylic acid, ketonic acid and alcoholic in CO2 and CO on heating. In the CO2 profile, the maximum in the temperature range 580-640 K is assigned to carboxyl groups.
4.3, In the CO2 profile of CCC & SCC, the peak observed at about 323-523 K corresponds to the presence of carboxylic groups.
Adsorption studies
The PZC of different CC samples shown in Table 4.2, activated by different treatments, was determined according to the standard procedure already mentioned in chapter 3. 2: PZC of activated CC charcoal. 5: PCC performance: (a) % adsorption with 100 mg adsorbent dosage (b) adsorption capacity of a 100 mg adsorbent dosage unit (c) % adsorption for 10 mg/L. 6: CCC performance: (a) % adsorption with 100 mg adsorbent dose (b) unit adsorption capacity for 100 mg adsorbent dose (c) % adsorption for 100. d) unit adsorption capacity for 100 mg/L MB conc.
7:Performance of SCC (a) % adsorption with 100 mg adsorbent dose (b) adsorption unit capacity for 100 mg adsorbent dose (c) % adsorption for 100. d) adsorption unit capacity for 100 mg/L MB conc.
Adsorption isotherm
8: Langmuir adsorption isotherm of MB at 300 K on NCC: (a) For adsorbent dose of 100 mg with different MB conc.
Adsorption kinetics
9: Pseudo second-order kinetics for adsorption of MB on NCC (a) For adsorbent dose 100 mg with MB conc. Other models that were investigated to study adsorption kinetics are intraparticle diffusion and the Evolich model.
Thermodynamic parameters
4.10, is drawn to calculate the thermodynamic parameters, change in enthalpy ΔH and change in entropy ΔS as summarized in Table 4.17.
Conclusion
The present study demonstrates a viable approach for the preparation of tailored carbons from the bio-waste corn cobs and their potential to remove MB from aqueous streams. Removal of Basic Dyes (Rhodamine B and Methylene Blue) from Aqueous Solutions Using Bagasse Fly Ash. Removal of anions, heavy metals, organics and dyes from water by adsorption on ZnCl2-activated coir carbon.
Adsorption studies on the removal of hexavalent chromium from aqueous solution using an inexpensive fertilizer industry waste material. Use of Sagaun sawdust as an adsorbent for the removal of crystal violet dye from simulated wastewater.
