Biochar, which is rich in aromatic carbon and minerals, is a product of biomass pyrolysis at temperatures ranging from 350°C to 1000°C in oxygen-limited environments. In recent years biochar has generated much interest in the field of water treatment in view of low production costs, availability of the feedstock (e.g. lignocellulosic biomass waste) and adsorptive properties. This review incorporates researches on artificial and natural modifications of biochar towards adsorption of potentially toxic elements on biochar. The aim of this study was to provide a comprehensive review of recent research findings and theory developments on the existing modifications of biochar for adsorption of potentially toxic elements (i.e. inorganic compounds) from aqueous solutions. Factors affecting adsorption of potentially toxic elements by lignocellulosic biochar and modification techniques for lignocellulosic biochar towards enhanced adsorption of potentially toxic elements were analyzed. The novelty of this study is discussion of the natural modifications of biochar and smart properties of biochar towards adsorption of potentially toxic elements. Recommendations are offered for modifying the lignocellulosic biochar to produce designed, engineered or smart biochar with high adsorption capacity for potentially toxic elements. Key words: engineered biochar; adsorption; lignocellulosic biomass; pyrolysis IntroductionAccording to European Biochar Certificate 2015, biochar 'is a heterogeneous substance rich in aromatic carbon and minerals. It is produced by pyrolysis of the sustainably obtained biomass under controlled conditions with clean technology and is used for any purpose that does not involve its rapid mineralization to CO2 and may eventually become a soil amendment'. At the beginning of biochar research, it aroused much interest as a soil amendment because of its potential for carbon sequestration and soil quality improvement. After physical, chemical and biological properties of biochar (Sun et al., 2014) and production technologies (Nartey and Zhao, 2014) were investigated, biochar research shifted from soil improvement to application in health sciences and engineering. Biochar could be a new low-cost adsorbent for removal of inorganic compounds (e.g. potentially toxic elements). It can be produced from wastes (e.g. lignocellulosic biomass) and is cheaper than activated carbon because it is produced through single-stage pyrolysis at 350-1000 °C and does not need additional costs in the activation process. Activation is the second stage in the production of activated carbon and occurs in the temperature range of 600-1200 °C in the presence of oxidizing gas, e.g. CO2 or steam, which results in the formation of a well-developed micropore structure. Therefore, biochar requires less energy for production than activated carbon (Azargohar and Dalai, 2006) and can be used as an alternative adsorbent to remove potentially toxic elements (PTE) from water solutions and air (Baltrėnaitė et al., 2016a). It demonstrated the ability ...
In this paper, the numerical algorithms for solution of pore volume and surface diffusion model of adsorption systems are constructed and investigated. The approximation of PDEs is done by using the finite volume method for space derivatives and ODE15s solvers for numerical integration in time. The analysis of adaptive in time integration algorithms is presented. The main aim of this work is to analyze the sensitivity of the solution with respect to the main parameters of the mathematical model. Such a control analysis is done for a linearized and normalized mathematical model. The obtained results are compared with simulations done for a full nonlinear mathematical model.
Abstract. Due to high specific surface area, well-developed porous structure and surface functionality biochar has a potential for being used as low-cost adsorbent for adsorption of organic and inorganic contaminants from aqueous solutions. Higher adsorption capacity and selectivity for metals could be further developed after modification of properties of biochar through physical ("designed biochar") and chemical ("engineered biochar") modification techniques. Wood waste of three types [aspen (Populus tremula L.), pine (Pinus sylvestris L.) and fir (Picea abies L.)] were selected to produce the biochar under slow pyrolysis conditions at 450 °C for 2 h with the heating rate of 10 °C/min. Mg and Fe-particles, acting as potential sorption sites for adsorption of metals, were added into the biochar through modification of the biochar with metal salts MgCl2 and FeCl3. The aim of the study was to investigate the effect of chemical modifications of woody biochar with MgCl2 and FeCl3 on the adsorption characteristics of the biochar. The engineered biochar with improved physico-chemical and sorptive properties was evaluated as potential adsorbent of metals from aqueous solutions. Such characteristics of the biochar, as density, porosity, pH, cation exchange capacity, electrical conductivity, moisture content, ash content, water holding capacity, total organic carbon were analyzed. Modifications followed by increasing of moisture and ash content. While carrying out the future adsorption experiment, significantly decreased pH and electrical conductivity of the engineered biochar should be taken into account. Increased cation exchange capacity of the engineered biochar promotes enhanced adsorption of metals.
Due to population growth and rapid development of industrialization, the spread of a wide range of potentially toxic elements (PTEs) in surface water and groundwater has become a critical issue worldwide. PTEs persisting in wastewater include heavy metals, inorganic compounds, organic pollutants and other complex compounds. The most common cationic PTEs in wastewater, like Pb(II), Zn(II), Cu(II), Cr(III, IV, VI), Ni(II), and Cd(II), are long-term pollutants and cannot degrade naturally. If present in excessive concentrations, they may be hazardous to human health and inhibit plant growth. The Baltic Marine Environment Protection Commission (HELCOM) has referred these metals to its list of priority contaminants. A variety of treatment technologies are available with different degrees of success to control and minimize wastewater pollution with PTEs. The usual concentration of these metals in wastewater solution is low (Cr 0.
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