Abstract
This work presents a comparison between the biosorption of Hg (II) by raw almond shell and activated almond shell. Almond shell based activated carbon has been obtained by physicochemical activation. Batch biosorption results confirmed that, activating condition has a strong influence on the final biosorption process. The biosorbent was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. To optimize the biosorption conditions pH, adsorbent dose, initial concentration, contact time, stirring speed, and temperature on Hg (II) removal were studied. The optimum conditions for maximum Hg (II) was achieved at 20 and 10 min for raw almond shell and activated almond shell, respectively. The equilibrium data were described well by Langmuir, Freundlich, Dubinin–Radushkevich isotherm models and appling a test of model fitness. Best fit of Langmuir and Freundlich models were found for experimental data, which reveal the homogenous surface of raw almond shell and the heterogeneity of activated almond shell surface. The kinetic data had been divided into either pseudo first order or second order on the basis of the best fit obtained from calculations, confirmed by a test of kinetic validity. An industrial application was examined to improve high biosorption capacity of raw and activated almond shells toward Hg (II).
Highlights
Due to toxic metals in industrial wastewaters, water pollution has become a major issue worldwide
As a preliminary kinetic test revealed that biosorption equilibrium of mercury on the Raw almond shell (RAS) or Activated almond shell (AAS) achieved within approximately 60 min under the experimental conditions, an equilibrium time of 60 min was adopted for all biosorption testing
This work explains a comparative study between RAS and AAS for the removal of Hg (II) ions
Summary
Due to toxic metals in industrial wastewaters, water pollution has become a major issue worldwide. Governments have established environmental restrictions with regard the quality of wastewater, forcing industries to remove metals from their effluents before discharging. Hg and its compounds have drawn much attention due to persistence, bioaccumulation, nonbiodegradability and can bind with organic and inorganic matter and form various composites, which limit water use. It is present in the environment from both natural sources and anthropogentic activities and the latter are believed to be responsible for the elevated mercury levels in the environment. Mercury released to the environment can be further converted to monomethylmercury (MMHg), a substance much more toxic than inorganic mercury (Cui et al, 2013; Harmayani and Anwar, 2016; Li et al, 2013; Ronda et al, 2013; Sun et al, 2014; Wang et al, 2013; Zhang et al, 2014)
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