Open AccessSulfuric Activated Carbon of Black Cumin (Nigella sativa L.) Seeds for the Removal of Cadmium(II) and Methylene Blue Dye
Author(s) -
Patience Mapule Thabede,
Ntaote David Shooto,
Thokozani Xaba,
Eliazer Bobby Naidoo
Publication year - 2020
Publication title -
asian journal of chemistry/asian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.145
H-Index - 34
eISSN - 0975-427X
pISSN - 0970-7077
DOI - 10.14233/ajchem.2020.22597
Subject(s) - methylene blue , chemistry , nuclear chemistry , freundlich equation , adsorption , activated carbon , langmuir , endothermic process , langmuir adsorption model , enthalpy , organic chemistry , catalysis , physics , thermodynamics , photocatalysis
Carbon from black cumin seeds was modified with 10 and 20% sulfuric acid to obtain the activatedadsorbents. Pristine carbon from black cumin seeds, 10 and 20% H2SO4 activated carbon from blackcumin seeds were labelled CBC, ACBC-10 and ACBC-20, respectively. The adsorbents werecharacterized by SEM, XRD, FTIR, TGA and BET. The adsorbents maximum trend for Cd(II) wasACBC-10 > ACBC-20 > CBC. The maximum capacity trend for methylene blue dye was ACBC-20 >ACBC-10 > CBC. The kinetic model best fitted pseudo second order for Cd(II) which gave r2 valuesof 0.991-0.998. The methylene blue fitted pseudo first order model with r2 values ranging from0.993-0.997. Pseudo first order suggested that the adsorption mechanism for methylene blue ontoadsorbents involved van der Waal forces of attraction. The equilibrium data fitted Langmuir isothermmodel for CBC, ACBC-10 and ACBC-20 with r2 of 0.994 to 0.998 for the removal of methylene bluewhilst the removal of Cd(II) followed Freundlich with r2 ranging from 0.992 to 0.997. This suggestedthat the different adsorption processes were involved between the adsorbate and the adsorbents. Gibb′sfree energy (ΔGº) for Cd(II) and methylene blue onto CBC, ACBC-10 and ACBC-20 suggested thatthe reaction was spontaneous. The adsorption of Cd(II) and methylene blue was endothermic, positivevalues (ΔHº). This suggested that the enthalpy (ΔHº) had a weak interactive force process whose lowenergy is associated with electrostatic attraction.