Effects of the biochar aromaticity and molecular structures of the chlorinated organic compounds on the adsorption characteristics

Abstract

Adsorption behaviors of the chlorinated organic compounds (COCs) (i.e., trichloroethylene (TCE), 1,2,4-trichlorobenzene (1,2,4-TCB); 1,2-dichlorobenzene (1,2-DCB); and monochlorobenzene (MCB)) by the commercial rice husk-based biochar (RH500) and the laboratory-prepared biochars from corn stalks under different pyrolytic temperatures (i.e., CS300, CS500, CS700) were examined and interpreted by the pseudo-first-order kinetic model, the double layer model with two energies, and the Freundlich model. It is identified that the first-order adsorption rate constants (k = 0.06∼0.51 h) were proportional to the high aromaticity and/or low polarity of biochars and the strong hydrophobicity of the COCs. The saturated adsorption capacity for the COCs was followed by the order of RH500 > CS500 > CS700 > CS300. RH500 showed the highest adsorption capacity for the COCs due to its high surface area (SA) and total pore volume (TPV). However, CS500 with low SA and TPV development highlighted the important roles of the aromaticity and/or low polarity on the COCs adsorption. In addition, 1,2,4-TCB showed the highest saturated adsorption capacity on all biochars, followed by TCE, 1,2-DCB, and MCB. The results further revealed the positive effects of the physical properties (α, N , ε, and ε ), the hydrophobicity and electrostatic forces (i.e., π-π interaction and electron donor-acceptor interaction) between the adsorbates and the aromatic moieties of biochar surfaces on the adsorption of COCs.

Biochar produced from Amazonian agro-industrial wastes: properties and adsorbent potential of Cd2+ and Cu2+

“…1 FTIR spectra of BA (A); BN (B) and BK (C) in pyrolysis of 400, 500, 600 and 700 °C are related to the degradation of surface functional groups (Fig. 1) and dehydration, depolymerization, and volatilization processes (Han et al 2017b;. The N content did not vary with pyrolysis temperature.…”

Applying Cassava Stems Biochar Produced from Agronomical Waste to Enhance the Yield and Productivity of Maize in Unfertile Soil

“…Atomic ratios of elements, including aromaticity (H/C ratio) and polarity (O/C ratio), were essential to evaluate the stability of biochar in the soil [53,63,78]. Therefore, CSB with the low value of the H/C ratio indicated that CSB had high aromaticity with increased resistance in the soil.…”

“…Anionic functional groups such as -OH, -COOH, and -C(=O)H, -CHO formed and occurred on the surface area [30,43,62]. By contrast, the acidic functional groups were removed [39,43,62,63]. Cellulose and lignin degradation and formation of the channel structure increased the surface area and pore volume of biochar [12,16,30,48], while pyrolysis temperature influenced the molecular structure and pores size distribution [30,34,43,48].…”

“…These reasons showed that the results of CSB had more significant surface area and total pore volume than feedstocks, while average pore diameter was less than feedstocks. As mentioned above, the structure of biochar thereby affected the adsorption characteristics [10,25,47,56,63], including nutrient absorption in the soil.…”

“…Although the previous studies had shown that biochar effectively increased productivity and improved soil properties [25,27,56,62,63], using biochar for agriculture should also be continuously studied due to the difference of the cultivation environment, different cultivation patterns and to solve the area's specific conditions and problems. Research on biochar produced from local feedstocks is an important and good choice for farmers [6], and the appropriate ratio of biochar used with soil resources is necessary for farmers to use widely.…”