Mandu Inyang

Effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil.

When applied to soils, it is unclear whether and how biochar can affect soil nutrients. This has implications both to the availability of nutrients to plants or microbes, as well as to the question of whether biochar soil amendment may enhance or reduce the leaching of nutrients. In this work, a range of laboratory experiments were conducted to determine the effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil. A total of thirteen biochars were tested in laboratory sorption experiments and most of them showed little/no ability to sorb nitrate or phosphate. However, nine biochars could remove ammonium from aqueous solution. Biochars made from Brazilian pepperwood and peanut hull at 600°C (PH600 and BP600, respectively) were used in a column leaching experiment to assess their ability to hold nutrients in a sandy soil. The BP600 biochar effectively reduced the total amount of nitrate, ammonium, and phosphate in the leachates by 34.0%, 34.7%, and 20.6%, respectively, relative to the soil alone. The PH600 biochar also reduced the leaching of nitrate and ammonium by 34% and 14%, respectively, but caused additional phosphate release from the soil columns. These results indicate that the effect of biochar on the leaching of agricultural nutrients in soils is not uniform and varies by biochar and nutrient type. Therefore, the nutrient sorption characteristics of a biochar should be studied prior to its use in a particular soil amendment project.

Removal of heavy metals from aqueous solution by biochars derived from anaerobically digested biomass.

This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb(2 +), Cu(2+), Ni(2+), and Cd(2+)) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM-EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200mmol/kg, which is comparable to that of commercial activated carbons.

Biochar derived from anaerobically digested sugar beet tailings: Characterization and phosphate removal potential

Two biochars were produced from anaerobically digested and undigested sugar beet tailings through slow-pyrolysis at 600°C. The digested sugar beet tailing biochar (DSTC) and raw sugar beet tailing biochar (STC) yields were around 45.5% and 36.3% of initial dry weight, respectively. Compared to STC, DSTC had similar pH and surface functional groups, but higher surface area, and its surface was less negatively charged. SEM-EDS and XRD analyses showed that colloidal and nano-sized periclase (MgO) was presented on the surface of DSTC. Laboratory adsorption experiments were conducted to assess the phosphate removal ability of the two biochars, an activated carbon (AC), and three Fe-modified biochar/AC adsorbents. The DSTC showed the highest phosphate removal ability with a removal rate around 73%. Our results suggest that anaerobically digested sugar beet tailings can be used as feedstock materials to produce high quality biochars, which could be used as adsorbents to reclaim phosphate.

Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings.

Biochar converted from agricultural residues or other carbon-rich wastes may provide new methods and materials for environmental management, particularly with respect to carbon sequestration and contaminant remediation. In this study, laboratory experiments were conducted to investigate the removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings (DSTC). Batch adsorption kinetic and equilibrium isotherm experiments and post-adsorption characterizations using SEM-EDS, XRD, and FTIR suggested that colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous phosphate. Batch adsorption experiments also showed that both initial solution pH and coexisting anions could affect the adsorption of phosphate onto the DSTC biochar. Of the mathematical models used to describe the adsorption kinetics of phosphate removal by the biochar, the Ritchie N_th-order (N=1.14) model showed the best fit. Two heterogeneous isotherm models (Freundlich and Langmuir-Freundlich) fitted the experimental isotherm of phosphate adsorption onto the biochar better than the Langmuir adsorption model. Our results suggest that biochar converted from anaerobically digested sugar beet tailings is a promising alternative adsorbent, which can be used to reclaim phosphate from water or reduce phosphate leaching from fertilized soils. In addition, there is no need to regenerate the exhausted biochar because the phosphate-laden biochar contains abundance of valuable nutrients, which may be used as a slow-release fertilizer to enhance soil fertility and to sequester carbon.

Preparation and characterization of a novel magnetic biochar for arsenic removal

A magnetic biochar based adsorbent with colloidal or nanosized γ-Fe(2)O(3) particles embedded in porous biochar matrix was fabricated via thermal pyrolysis of FeCl(3) treated biomass. The synthesized samples were studied systematically by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, selected-area electron diffraction pattern, scanning electron microscopy, energy-dispersive X-ray analysis, superconducting quantum interference device, and batch sorption measurements. The characterization analyses showed that large quantity of γ-Fe(2)O(3) particles with size between hundreds of nanometers and several micrometers tightly grow within the porous biochar matrix. Biochar/γ-Fe(2)O(3) composite exhibited excellent ferromagnetic property with a saturation magnetization of 69.2emu/g. Batch sorption experimental results showed that the composite has strong sorption ability to aqueous arsenic. Because of its excellent ferromagnetic properties, the arsenic-laden biochar/γ-Fe(2)O(3) composite could be easily separated from the solution by a magnet at the end of the sorption experiment.

Biochar from anaerobically digested sugarcane bagasse

This study was designed to investigate the effect of anaerobic digestion on biochar produced from sugarcane bagasse. Sugarcane bagasse was anaerobically digested to produce methane. The digested residue and fresh bagasse was pyrolyzed separately into biochar at 600 degrees C in nitrogen environment. The digested bagasse biochar (DBC) and undigested bagasse biochar (BC) were characterized to determine their physicochemical properties. Although biochar was produced from the digested residue (18% by weight) and the raw bagasse (23%) at a similar rate, there were many physiochemical differences between them. Compared to BC, DBC had higher pH, surface area, cation exchange capacity (CEC), anion exchange capacity (AEC), hydrophobicity and more negative surface charge, all properties that are generally desirable for soil amelioration, contaminant remediation or wastewater treatment. Thus, these results suggest that the pyrolysis of anaerobic digestion residues to produce biochar may be an economically and environmentally beneficial use of agricultural wastes.

A review of biochar as a low-cost adsorbent for aqueous heavy metal removal

ABSTRACT As a low-cost adsorbent, biochar can be used as a low-cost adsorbent for wastewater treatment, particularly with respect to treating heavy metals in wastewater. A number of studies have demonstrated effective removal of heavy metals from aqueous solutions by biochar and, in some cases, proven the superiority of biochars to activated carbons. Among several factors affecting the sorption ability of biochars, feedstock materials play a significant role. This review incorporates existing literature to understand the overall sorption behavior of heavy metals on biochar adsorbents. Depending on the biochar type, heavy metal can be removed by different mechanisms such as complexation, physical sorption, precipitation and electrostatic interactions. Mathematical sorption models can be used to understand the efficiency of biochar at removing heavy metals, and promote the application of biochar technology in water treatment.

Adsorption of sulfamethoxazole on biochar and its impact on reclaimed water irrigation

Reclaimed water irrigation can satisfy increasing water demand, but it may also introduce pharmaceutical contaminants into the soil and groundwater environment. In this work, a range of laboratory experiments were conducted to test whether biochar can be amended in soils to enhance removal of sulfamethoxazole (SMX) from reclaimed water. Eight types of biochar were tested in laboratory sorption experiments yielding solid-water distribution coefficients (K(d)) of 2-104 L/kg. Two types of biochar with relatively high K(d) were used in column leaching experiments to assess their effect on reclaimed water SMX transport through soils. Only about 2-14% of the SMX was transported through biochar-amended soils, while 60% was found in the leachate of the unamended soils. Toxicity characteristic leaching experiments confirmed that the mobility and bioavailability of SMX in biochar-amended soils were lower than that of unamended soils. However, biochar with high accumulations of SMX was still found to inhibit the growth of the bacteria compared to biochar with less SMX which showed no effects. Thus, biochar with very high pharmaceutical sorption abilities may find use as a low-cost alternative sorbent for treating wastewater plant effluent, but should be used with caution as an amendment to soils irrigated with reclaimed water or waste water.

Enhanced Lead Sorption by Biochar Derived from Anaerobically Digested Sugarcane Bagasse

This study examined the ability of two sugarcane bagasse biochars to remove lead from water. The sorption of lead by biochars made from raw (BC) and anaerobically digested sugarcane bagasse (DBC) was compared with a commercial activated carbon (AC) using batch sorption experiments. DBC was a more effective sorbent of lead from water than AC, and far more effective than BC. The maximum lead sorption capacity of DBC (653.9 mmol kg−1) was about double that of AC (395.3 mmol kg−1) and about twenty times higher than that of BC (31.3 mmol kg−1). Post-sorption characterizations using X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the enhanced sorption of lead by DBC was at least partly related to a precipitation mechanism, while surface adsorption was the principal mechanism of sorption of lead onto BC. These results suggest that biochars made from bagasse and other agricultural residues may be effective alternative, low-cost environmental sorbents of lead or other metals. In addition, the enhanced lead sorption ability of the digested bagasse biochar introduces the possibility of developing a novel carbon production method to use anaerobic digestion as a means of biological activation to create high-efficiency sorbents.

Engineered carbon (biochar) prepared by direct pyrolysis of Mg-accumulated tomato tissues: Characterization and phosphate removal potential

An innovative method was developed to produce engineered biochar from magnesium (Mg) enriched tomato tissues through slow pyrolysis in a N2 environment. Tomato plants treated with 25mM Mg accumulated much higher level of Mg in tissue, indicating Mg can be substantially enriched in tomato plants, and pyrolysis process further concentrated Mg in the engineered biochar (8.8% Mg). The resulting Mg-biochar composites (MgEC) showed better sorption ability to phosphate (P) in aqueous solutions compared to the other four tomato leaves biochars. Statistical analysis showed a strong and significant correlation between P removal rate and biochar Mg content (R(2)=0.78, and p<0.001), indicating the enriched Mg in the engineered biochar is the main factor controlling its P removal ability. SEM-EDX, XRD and XPS analyses showed that nanoscale Mg(OH)2 and MgO particles were presented on the surface of MgEC, which serve as the main adsorption sites for aqueous P.