Equilibrium and kinetic studies on the adsorption of Ni(II) ion from an aqueous solution using activated carbon prepared from Theobroma cacao (cocoa) shell

Abstract

A B S T R A C TThe adsorption of Ni(II) ion from an aqueous solution was successfully carried out using activated carbon prepared from Theobroma cacao (cocoa) shell, an agricultural solid waste biomass. The activated carbon prepared at ambient temperature (TCAC1) and the one prepared at 350˚C (TCAC2) were characterised by the FT-IR, BET, SEM, EDAX and Particle size analysis methods. The effects of the pH, dosage, initial metal ion concentration and agitation time were studied. The maximum adsorption was observed at pH 6 and the adsorption equilibrium was attained within 60 min. Adsorption isotherm data have been analysed, and the data fitted well in the order Langmuir > Redlich-Peterson > Temkin > Freundlich isotherm models. The maximum adsorption capacities of TCAC1 and TCAC2 for Ni(II) ions were calculated from the Langmuir isotherm as 97.59 and 158.8 mg/g, respectively. The kinetics of Ni(II) ion adsorption has been described, using five kinetic models viz, the pseudo-first order, pseudo-second order, Elovich, Intra-particle diffusion and Boyd kinetic models. The pseudo-second order kinetic model fits well with good correlation values. Thermodynamic parameters such as gibbs free energy (ΔG˚), the enthalpy (ΔH˚) and the entropy change of adsorption (ΔS˚) have been calculated and it has been suggested that the adsorption process was feasible, spontaneous and exothermic in nature. The results obtained indicate that the activated cocoa shell prepared at 350˚C, has higher adsorption capacity when compared to the one prepared at room temperature. High surface area and low particle size are the prime factors for the increased efficiency.

Cocoa Shell: A By-Product with Great Potential for Wide Application

“…It is suggested as an opportunity to replace the commercial coal-based activated carbon, as it is an eco-friendly product [ 8 ]. There are a few different studies about this subject published by Ahmad et al [ 43 , 44 , 45 ], Kalaivani et al [ 46 ], Ribas et al [ 47 ], Saucier et al [ 48 ], and Plaza-Recobert et al [ 49 ].…”

“…Kalaivani et al [ 46 ] reported that activated cocoa shell carbon (TCAC1 and TCAC2) prepared at two different temperatures (30 and 350 °C) show considerable potential for the removal of Ni(II) ion from an aqueous solution. The heat treatment of the adsorbent has resulted in a smaller particle size and larger surface area and, as a result of the increase in adsorption capacity, shows almost 62% higher efficiency in Ni (II) removal, when compared with TCAC1.…”

Removal of Pb(II) using Hydroxyapatite from Golden Snail Shell (Pomacea canaliculata L.) Modified with Silica

“…The silanol group releases H + and forms SiO-which can adsorb Pb(II) (Hu, Wang, & Pan, 2010). The value of n between 1 and 10 represents favorable adsorption (Kalaivani et al, 2014). This study obtained n > 1 for both hydroxyapatite and hydroxyapatite-SiO2 composite.…”

“…The pH of the solution affects the adsorption capacity of hydroxyapatite-SiO2 to Pb ions. The surface charge of the adsorbent is affected by the pH of the solution (Kalaivani, 2014). The pH of the solution in the adsorption process was studied at range 2-10 using 25 mL of 50 mg/L Pb(II) solution.…”

Hydroxyapatite-PEG/Fe₃O₄ Composite for Adsorption of Phenol from Aqueous Solution

“…This experiment used the pseudofirst order and pseudo-second order models. The former is expressed in the following equation [28]: (2) ...where q t and q 1 are the amounts of phenol adsorbed at t time and at equilibrium condition (mg g -1 ), respectively, while k 1 is the pseudo-first order constant (min -1 ) calculated via slope and intercept of a graph plotted between 1/q t vs 1/t.…”