Experimental Investigations on Adsorption of Reactive Toxic Dyes Using Hedyotis umbellate Activated Carbon

Table 1

Equations of adsorption functions.

Equation number	Adsorption function	Equation
1.	Equilibrium amount of dye adsorbed
2.	Removal efficiency,%
Where is the initial dye concentration, is the final dye concentration at equilibrium, is the operating volume of the solution, and is the mass of adsorbent.
Adsorption isotherms
3.	Langmuir isotherm
4.	Dimensionless separator factor
5.	Freundlich isotherm
6.	Temkin isotherm
Where is the amount of dye adsorbed per g, is the monolayer adsorption capacity, is Langmuir adsorption constant, is Freundlich constant, is Freundlich coefficient, is Temkin binding constant, and is Temkin isotherm constant.
Kinetic studies
7.	Pseudofirst order equation
8.	Pseudosecond order equation
9.	Intraparticle diffusion
Where is the amount of dye absorbed at equilibrium, is the amount of dye absorbed at any time , is the pseudofirst order rate constant in s^-1, is the pseudosecond order rate constant, is the intraparticle diffusion rate constant, and is the intercept.
Thermodynamic studies
10.	Gibbs equation
11.	Van’t Hoff equation
Where is the equilibrium constant, is Gibbs free energy change, is change in enthalpy of adsorption, is entropy change, and is the operating temperature.