ABSTRACT
Given the current importance of using biochar for water treatment, it is important to study the physical-chemical properties to predict the behavior of the biochar adsorbent in contact with adsorbates. In the present research, the physical and chemical characteristics of three types of biochar derived from banana leaves were investigated, which is a poorly studied raw material and is considered an agricultural waste in some Latin American, Asian, and African countries. The characterization of non-modified biochar samples pyrolyzed at 300, 400, and 500 °C was carried out through pH, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and specific surface area measurements. The adsorption properties of banana leaf-derived biochar were evaluated by ammonium ion adsorption experiments. The results demonstrated that the pyrolysis temperature has a large impact on the yield, structure, elemental composition, and surface chemistry of the biochar. Biochar prepared at 300 °C is the most efficient for NH4+ adsorption, achieving a capacity of 7.0 mg of adsorbed NH4+ on each gram of biochar used, while biochar samples prepared at 400 and 500 °C show lower values of 6.1 and 5.6 mg/g, respectively. The Harkins-Jura isotherm model fits the experimental data best for all biochar samples, demonstrating that multilayer adsorption occurs on our biochar.
ABSTRACT
Industrial, e.g. food industrial and domestic wastewaters contain huge amount of compounds causing eutrophication, and should be removed with high cost during wastewater treatment. However, these compounds could be utilized as fertilizers too. Biochar can remove a wide range of pollutants from water, such as ammonium, which can be found in relatively high concentration in dairy wastewaters. However, adsorption performance may be affected by the presence of other wastewater pollutants. Thus, this study aims to determine the efficiency of biochar as an adsorbent of ammonium in aqueous solutions in the presence of some selected organic compounds of typical dairy wastewaters such as bovine serum albumin (BSA), lactose, and acetic acid. Methods: The biochar was produced from banana leaves at 300 °C, modified with NaOH, and characterized by Scanning Electron Microscope - Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectra (FTIR) analysis, and specific surface area measurements. Batch experiments were carried out to investigate the ammonium adsorption capacity and the ion competitive adsorption mechanism. Significant Findings: Results show that the surface structure of the biochar derived from banana leaves is different from other biochars previously studied; although the specific surface area is not very considerable and despite having nitrogen within the elemental composition, the biochar studied is capable of adsorbing 2.60 mg NH4+/m2, the highest ammonium removal in 2 h occurs at pH 9 and 500 mg biochar dose. Langmuir model in the monolayer phase analysis fits better for all scenarios and the maximum NH4+ adsorption capacity was 0.97 mg/g without organic compounds. In the multilayer adsorption phase, the isotherm model that best fits the data obtained is the Harkins-Jura model without organic compounds. The presence of organic compounds in the aqueous solution significantly impacts the adsorption of ammonium by biochar since it improves the adsorption capacity (1.132 mg/g BSA, 0.975 mg/g lactose, and 1.874 mg/g acetic acid). The Aranovich-Donohue isotherm model fitted the data obtained during ion competitive adsorption experiments well.
