Effectiveness of Alkali-Acid Treatment in Enhancement the Adsorption Capacity for Rice Straw: The Removal of Methylene Blue Dye

Abstract

The effectiveness of alkali-acid modification in enhancement the adsorption capacity of rice straw (RS) for removing a basic dye was studied. The obtained adsorbents were characterized by slurry pH, pHPZC, iodine number, methylene blue number, FTIR, and SEM analyses. Adsorption of methylene blue (MB) was described by the Langmuir, Freundlich, Tempkin, and Redlich-Peterson isotherm models. Effects of contact time, initial concentration of MB dye, pH of solution, adsorbent dose, salt concentration of NaCl, and desorbing agents on the removal of MB were reported. Kinetic studies were analyzed using the pseudo-first-order, pseudo-second-order, and the intraparticle diffusion models and were found to follow closely the pseudo-second-order model. Equilibrium data were best represented by the Langmuir and Redlich-Peterson isotherms. The adsorption capacities were varied between 32.6 and 131.5 mg/g for untreated and treated RS samples with NaOH-1M citric acid (ARS-1C), respectively. Adsorption behavior of the ARS-1C sample was experimented in a binary mixture containing methylene blue (basic) and reactive blue 19 (acidic) dyes which showed its ability to remove MB higher than RB19. Overall, the results indicate that the alkali-acid treatment proved to be potential modification for producing effective low-cost adsorbents for the removal of the basic dyes from wastewater.

Adsorption of methylene blue from aqueous solution using untreated and treated (Metroxylon spp.) waste adsorbent: equilibrium and kinetics studies

“…The high adsorption of SKOH between pH values of 6 and 10 can be attributed to electrostatic attraction between the negative charges of the adsorbent surface and the positive charge of the MB cation, since the amount of dye being removed was high ([140 mg/g) at For SHP at pH conditions above the pH PZC of 3.04, there was a trend toward increasing sorptive capacities as pH increased to 10. As the excess hydroxyl (-OH -) ions increased, surface functional groups were predominantly deprotonated resulting in an enhanced number of adsorption sites available for binding positively charged MB adsorbate [22,35].…”

“…These lignocellulosic byproducts possess various advantages, such as being ecofriendly, renewable, less expensive and abundantly available, as compared to commercial adsorbents [18,20]. Studies have also shown that chemical modification of agricultural by-products significantly enhances their ionbinding properties, thereby providing greater flexibility in their applications to a wide range of dyes [21][22][23][24]. However, while agricultural by-products are often presented as low-cost adsorbents, their availability is often region specific.…”

Nanostructured activated carbon xerogels for removal of methomyl pesticide

“…To study the adsorption capacity of the prepared carbons, the removal of methomyl was carried out in batch experiments to describe the equilibrium adsorption using three classical adsorption isotherm models as follows [36][37][38]:…”

“…Freundlich constants K F and n can be calculated from the intercept and slope of the linear plot with ln q e against ln C e . In the case of Temkin equation, B 1 = (RT/b) and K T are the Temkin constants [38]. K T is the equilibrium binding constant (L/mol) corresponding to the maximum binding energy, b is the variation of adsorption energy (J/mol), and constant B 1 is related to the heat of adsorption.…”

“…K T is the equilibrium binding constant (L/mol) corresponding to the maximum binding energy, b is the variation of adsorption energy (J/mol), and constant B 1 is related to the heat of adsorption. The Gibbs free energy, ΔG˚(kJ/mol), for the adsorption process was obtained at 25˚C (ΔG˚=−RT ln K L [38], where R is the universal gas constant at STP, 8.314 J/mol K, and T is the absolute temperature in Kelvin). Also, Table 3 lists surface density (mmol/m 2 ) which is known as the adsorbed amount of methomyl (mmol/g) as a function of the total surface area of ACX adsorbent (m 2 /g) [20].…”