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In recent years, biochar has been extensively studied as a sorbent for immobilizing contaminants and minimizing their bioavailability in soils. Few studies have been conducted to evaluate the interactions between biochar and compost in soils and their impact on degradation of organic contaminants. In the present study, soils with high organic carbon content (HOC) and low organic carbon content (LOC) were spiked with 100 mg·kg − 1 di-(2-ethylhexyl) phthalate (DEHP) amended with biochar derived from dead pigs, bamboo, and composted sheep manure. The soils were thereafter incubated for 112 days at 25 °C and periodically sampled for monitoring DEHP concentrations. Degradation of DEHP was described by a logistic model. Results showed that the initial degradation rates were slow, but accelerated after 14 days of incubation. The DEHP degradation rates were higher in the HOC soils than in the LOC soils over the incubation period. The half-lives of DEHP were shorter in the LOC soils treated with pig biochar, and bamboo/pig biochar plus compost than in the untreated soil. However, there was no significant difference in the half-lives of DEHP in the HOC control and treated soils. The differential effects of soil amendments on DEHP degradation between LOC and HOC soils could be explained by the properties of the organic amendments, soil pH and the organic carbon contents of the soils. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to evaluate the effect of biochars on the bioavailability of di-(2-ethylhexyl) phthalate (DEHP) in two soils using Brassica chinensis L. as an indicator plant. The residual concentrations of DEHP tended to be higher in the biochar-amended soils than in the control soils. They were lower ( p < 0.05) in the high organic carbon content soil (HOC; 2.2%C) than in the low organic carbon content soil (LOC; 0.35%C). The DEHP concentrations in plant shoots grown in the HOC soils were lower than those in the LOC soils ( p < 0.05). Compared to the control, the biochar addition decreased the DEHP concentrations in shoots grown in the LOC soils; whereas there was no significant difference in the HOC soils. Our results showed that soil OC content as well as biochar properties are the key factors influencing the bioavailability of DEHP in soils. [ABSTRACT FROM AUTHOR]

Pollution of water by single antibiotics has been investigated in depth. However, in reality, a wide range of different contaminants is often mixed in the aquatic environment (contaminant cocktail). Here, single and competitive sorption dynamics of ionizable norfloxacin (NOR), sulfamerazine (SMR) and oxytetracycline (OTC) by both pristine and modified biochars were investigated. Sorption kinetics of the three antibiotics was faster in ternary-solute than single-solute system. Sorption efficiency was enhanced in the competitive system for NOR by the pristine biochar, and for OTC by both the pristine biochar and the modified biochar, while SMR sorption by the pristine biochar and the KOH-modified biochar was inhibited. Sorption was governed by electrostatic interactions, π-π EDA and H-bonds for antibiotics sorption by biochar. SMR and OTC sorption by biochar was influenced by cation bridging and surface complexation, respectively. This research finding will guide the development of treatment procedures for water polluted by multiple antibiotics. [ABSTRACT FROM AUTHOR]

In this study, we examined the efficacy of nine different types of coconut-fiber derived biochars (CFBs), prepared at different temperatures and chemically modified with ammonia, hydrogen peroxide and nitric acid, to remove lead (Pb 2 + ) from aqueous solutions. Langmuir- q m values of the biochars pyrolyzed at 300 °C and modified with ammonia and nitric acid increased from 49.5 to 105.5 and 85.2 mg g − 1 , respectively, compared to control (unmodified), whereas hydrogen peroxide treatment had no effect. The maximum amount of Pb adsorbed on biochars was in the order of CFB-700 > MCFB-300-NH 3 ·H 2 O > CFB-500 > MCFB-300-HNO 3 > CFB-300. X-ray absorption fine structure (XAFS) spectroscopy results revealed that Pb-montmorillonite, Pb(C 2 H 3 O 2 ) 2 , PbSO 4 , Pb-Al 2 O 3 and Pb 3 (PO 4 ) 2 were the five most important Pb species observed in Pb-loaded biochars, and as such, favoring Pb immobilization in aqueous solutions. Overall, the sorption capacity of CFBs pyrolyzed at 300 °C substantially increased for Pb 2 + with ammonia and nitric acid modification. However, these chemical modifications did not improve the sorption of Pb on CFBs pyrolyzed at temperatures ≥ 500 °C, thereby highlighting a temperature dependent response of chemically modified biochars to Pb sorption in this study. [ABSTRACT FROM AUTHOR]

In this study, the influence of the aging process of pig-(PB) and P. orientalis -(POB) derived biochars on the sorption capacity of the biochar-treated soils for cadmium (Cd) and zinc (Zn) with and without the co-existence of diethyl phthalate (DEP) was investigated. Additionally, the surface and internal characteristics of biochars were determined before and after their aging in soils. The PB-treated soil had a higher sorption capacity for Cd2+ and Zn2+ than the POB-treated soil. The sorption capacity of the biochar-treated soils for Cd2+ and Zn2+ increased with biochar application rates. After aging, the abundance of oxygen-containing functional groups on the biochar surface, and the pH and organic carbon content of the biochar-treated soils significantly increased, thereby improving the sorption capacity for Cd2+ and Zn2+. The sorption capacities of biochar-treated soils for Cd2+ and Zn2+ followed the order of 1-month aging > 6-month aging > fresh. The co-existence of DEP enhanced the sorption capacity of the fresh biochar-treated soils for Cd2+ and Zn2+, whereas this enhancing effect disappeared for the aged biochar treatments. Our findings provide insights into the interactions between mixed contaminants in biochar-amended soils and the long-term efficacy of biochar treatments on metal sorption to soils. ga1 • Aging process enhanced Cd2+ and Zn2+ sorption on biochar-treated soils. • Pig biochar was better than wood biochar in enhancing soil sorption of metals. • Diethyl phthalate (DEP) enhanced sorption of metals in biochar-treated soils. • However, DEP suppressed metal sorption in aged biochar-treated soils. [ABSTRACT FROM AUTHOR]

• The hydrochar-derived DOM-mediated reduction of δ -MnO 2 released aqueous Mn(II). • Hydrochar-derived DOM was transformed via both decomposition and polycondensation. • The molecular characteristics of reacted DOM were more similar to NOM. Hydrochar produced from hydrothermal carbonization of agricultural waste becomes a promising soil conditioner, and especially, its labile fraction, dissolved organic matter (DOM) may play an important role in improving soil fertility and quality. However, little is known about the interaction and transformation of hydrochar-derived DOM with soil reactive components after its amendment into soil. The abiotic transformation of hydrochar-derived DOM by a common soil metal oxide, δ -MnO 2 at environmentally relevant pHs (4, 6 and 8) was investigated by using a combination of batch experiments and advanced spectroscopic techniques. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and fluorescence spectroscopy revealed that lignins and carboxyl-rich alicyclic molecules were predominant in hydrochar-derived DOM and phenolic fluorophores were the dominant fluorescent composition. In the presence of δ -MnO 2 , hydrochar-derived DOM was rapidly transformed via both decomposition and polycondensation, resulting in significant structure changes of hydrochar-derived DOM with increasing humic-like fraction similar to soil organic matter (SOM). The transformation process of hydrochar-derived DOM molecules was highly pH-dependent, with polycondensation occurring preferentially at pH 8 and more rapid oxidation at pH 4. Meanwhile, δ -MnO 2 was reduced to Mn(II) and Mn(III) during the reaction, and the accumulation of Mn(III) in the solid phase of δ -MnO 2 reached a maximum at pH 4. Collectively, the results characterized the transformation mechanism of DOM by δ -MnO 2 at molecular level, which provided a new perspective for better understanding of the biogeochemical processes of biochar for its application in soil quality improvement and remediation. [ABSTRACT FROM AUTHOR]