Abstract
Water pollution by heavy metals like Co(II) is particularly of concern because of their persistence in the environment, toxicity, and ability to bioaccumulate in organisms. In this study, the influence of contact time at three initial concentration, pH, adsorbent dose, temperature, and kinetics, thermodynamics, and one-, two-, and three-parameter isotherm modeling of the adsorption of Co(II) on neem leaves (DNL) was investigated. The adsorbent was characterized using FTIR, TGA-DSC, EDX, and nitrogen adsorption-desorption. DNL is composed of many Co(II) surface-binding groups and a BET surface area of 0.2783 m2/g dominated by meso- and macropores. Equilibrium was attained in 10 minutes for the three concentrations with a removal efficiency of 85–97%. ∆G° of −5.424 to −6.068 KJ/mol at 25 to 60°C, respectively, indicated spontaneous adsorption with increasing temperature. D-R adsorption energies of 0.649 to 2.433 KJ/mol revealed physical adsorption. Maximum adsorption capacity of 9.201–523.900 mg/g was obtained by Freundlich and Jovanovic isotherms. Adsorption was very favourable as evident by the high Kiselev equilibrium constant (11.652–172.78 L/mg) and very lowRLvalues of 0.001–0.026. Adsorption occurred by repulsive mechanism as indicated by Fowler–Guggenheim and Hill–de Boer negative interaction energies (−16.182 to −90.163 and −111.102 to −3328.86 KJmol−1,respectively), confirming maximum Co(II) adsorption at pH 3. Results can be used in the design of an efficient adsorption system using neem leaves which is very efficient in removing low and high levels of heavy metals like cobalt ions from wastewater.
Highlights
Water pollution by heavy metals like Co(II) is of concern because of their persistence in the environment, toxicity, and ability to bioaccumulate in organisms
Water pollution by the group of pollutants called heavy metals is on the rise worldwide and is of concern because of their persistence in the environment, toxic in trace amounts, and ability to induce severe oxidative stress and ability to bioaccumulate in organisms [2]
For Fourier-transform infrared spectroscopy (FTIR), the peaks obtained were compared with those of neem leaves and other biomass samples reported in the literature for identification. e different phase transformations were investigated using the differential scanning calorimetry-thermogravimetric (DSCTGA) techniques (SDT Q600 V20.9 Build 20, TGA-DTA, TA Instruments, USA)
Summary
Water pollution by heavy metals like Co(II) is of concern because of their persistence in the environment, toxicity, and ability to bioaccumulate in organisms. The influence of contact time at three initial concentration, pH, adsorbent dose, temperature, and kinetics, thermodynamics, and one-, two-, and three-parameter isotherm modeling of the adsorption of Co(II) on neem leaves (DNL) was investigated.
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