Preparation of Activated Carbon from the Wood of Paulownia tomentosa as an Efficient Adsorbent for the Removal of Acid Red 4 and Methylene Blue Present in Wastewater

Abstract

Paulownia tomentosa, a woody plant that is widely found in Pakistan and in other regions of the world, was used as a raw material to prepare activated carbon using chemical and physical activation methods. Adsorption of the dyes- acid red 4 and methylene blue onto the prepared activated carbon were analyzed by batch experiments. The impacts of different adsorption parameters such as pH, temperature, contact time, initial dye concentration and adsorbent dosage were also evaluated. Equilibrium data were fitted into various isotherm models such as: Langmuir, Temkin and Freundlich. High regression values were achieved with Langmuir isotherm model. Different kinetic adsorption models such as pseudo-first-order, pseudo-second-order and intra-particle diffusion model models were applied. The adsorption kinetics was found to be best-fitted into pseudo-second-order kinetic model. The optimum pH for acid red 4 was around 1 while for methylene blue it was 8. The optimum adsorbent dosage was 0.3 g for both dyes used. The activation energy (Ea) values were 30.57 and 3.712 kJ/mol, respectively for acid red 4 and methylene blue while the enthalpy (ΔH) and entropy (ΔS) values were correspondingly as 24.88/1.1927 kJ/mol and −2843.32/−0.329 J·mol/K for the mentioned dyes. The experimental result showed that the prepared activated carbon was the best in the removal of acid red 4 and methylene blue from aqueous media and therefore, could be preferably used as cheap adsorbent in wastewater treatment.

Effective Poly (Cyclotriphosphazene-Co-4,4′-Sulfonyldiphenol)@rGO Sheets for Tetracycline Adsorption: Fabrication, Characterization, Adsorption Kinetics and Thermodynamics

“…The Langmuir and Freundlich isotherm models were applied to reveal insights into the adsorption phenomena. The Langmuir isotherm model assumes that the molecules are adsorbed in a monolayer configuration on the adsorbent surface where all the adsorption sites possess the same energy, so the adsorption of a species is identical [48][49][50]. In comparison, the Freundlich isotherm model states multilayer, non-ideal adsorption, and the adsorption sites are unevenly distributed, involving a different affinity for adsorbing molecules.…”

Activated Ailanthus altissima Sawdust as Adsorbent for Removal of Acid Yellow 29 from Wastewater: Kinetics Approach

“…The peak at 1582 cm −1 represents COO-deprotonated carboxylate group. The peak observed at 1328 cm −1 suggests the stretching vibrations of pectin (-COOH) [16]. The obtained peak at 1233 cm −1 shows hemicellulose C-O stretching vibration and suggests the importation of hemicellulose C-O vibration.…”

“…For understanding the kinetics of the adsorption of adsorbate (dye) on the adsorbent, the concept of Lagergren or pseudo first order kinetics model was used. The following straight line Equation (1) was used to determine kinetics constants [16][17][18]:…”

“…where dt is change in time, C dφ is the amount of adsorbed (mg/g) dye on the adsorbent (sawdust), C de is the equilibrium potential of adsorption in mg/g and k 1 is the rate constant/minutes. Moreover, logarithmic form of the equation can be given by Equation (2) [16][17][18]:…”

“…This model is used to explain the adsorption phenomenon of kinetics of adsorption that basically determine the rate limiting step. It can be given mathematically as follows [16][17][18]:…”