Synthesis and phosphate adsorption performance of elephant dung biochar modified with magnesium and iron (original) (raw)
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Reactivity of Fe-amended biochar for phosphorus removal and recycling from wastewater
PLOS Water
Using biochar to remove phosphorus (P) from wastewater has the potential to improve surface water quality and recycle recovered P as a fertilizer. In this research, effects of iron modification on P sorption behavior and molecular characterization on two different biochars and an activated carbon were studied. A biochar produced from cow manure anaerobic digest fibers (AD) pyrolyzed under NH3 gas had the greatest phosphate sorption capacity (2300 mg/kg), followed by the activated carbon (AC) (1500 mg/kg), and then the biochar produced from coniferous forest biomass (BN) (300 mg/kg). Modifying the biochars and AC with 2% iron by mass increased sorption capacities of the BN biochar to 2000 mg/kg and the AC to 2300 mg/kg, but decreased sorption capacity of the AD biochar to 1700 mg/kg. Molecular analysis of the biochars using P K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that calcium phosphate minerals were the predominant species in the unmodified biocha...
Modification of Hardwood Derived Biochar to Improve Phosphorus Adsorption
Environments
The excessive application of phosphorus in agricultural lands leads to serious environmental issues. Efficient application is beneficial from an economic and environmental perspectives. Biochar can be used as a carrier for slow release of phosphate. However, its adsorption capacity is limited. In this work, biochar was prepared at different pyrolysis temperatures (350–550 °C). The biochar prepared at 550 °C had the highest adsorption capacity and was selected for modification by magnesium impregnation. Magnesium modification enhanced the adsorption capacity by 34% to a theoretical max adsorption capacity of 463.5 mg·g−1. The adsorbed phosphate can be desorbed. The desorption was bi-phasic with fast- and slow-release fractions. The distribution of the phosphate fractions was pH dependent with slow release being most prominent in neutral conditions. Mg modified biochar can be used to recover phosphate and then used as a carrier for slow release of phosphate. The bi-phasic desorption b...
Bioresource technology, 2016
The present study deals with the preparation of a novel MgO-impregnated magnetic biochar (MMSB) for phosphate recovery from aqueous solution. The MMSB was evaluated against sugarcane harvest residue biochar (SB) and magnetic biochar without Mg (MSB). The results showed that increasing Mg content in MMSB greatly improved the phosphate adsorption compared to SB and MSB, with 20% Mg-impregnated MMSB (20MMSB) recovering more than 99.5% phosphate from aqueous solution. Phosphate adsorption capacity of 20MMSB was 121.25mgP/g at pH 4 and only 37.53% of recovered phosphate was desorbed by 0.01mol/L HCl solutions. XRD and FTIR analysis showed that phosphate sorption mechanisms involved predominately with surface electrostatic attraction and precipitation with impregnated MgO and surface inner-sphere complexation with Fe oxide. The 20MMSB exhibited both maximum phosphate sorption and strong magnetic separation ability. Overall, phosphate-loaded 20MMSB significantly enhanced plant growth and c...
2019
This report examines several different strategies for creating engineered biochars from waste lignocellulosic materials with enhanced properties chosen specifically for their potential to integrate into urban waste processing biorefineries. Specifically, the goal was to improve capacity for adsorption of phosphates and hydrogen sulfide by chars derived from several lignocellulosic materials including fiber from anaerobically digested dairy manure (AD fiber), urban wood residuals, and wheat straw. The impacts on water holding capacity was also examined as this is an important function for biochar incorporated into soils. In the first generation (CO2-activated) biochar, a pyrolysis step is followed by an activation step with CO2. CO2-activated char from anaerobically digested (AD) fiber had phosphate adsorption capacity of 32.4 mg g-1 biochar. The hydrogen sulfide (H2S) adsorption capacity of AD fiber-derived chars was 51.2 mg g-1. The breakthrough time for adsorption of hydrogen sulfide for AD fiber-derived char produced at 750℃ compared favorably to commercial activated carbon. Second generation biochar was produced using “nitrogen doping” (the process of introducing nitrogen functional groups into a carbonaceous material). When nitrogen-doped char, produced using a single step process had a phosphate adsorption capacity nearly double that of char produced using a two-step process (110.3 mg g-1 vs. 63.1 mg g-1). Our team also conducted analysis of water holding capacity with N-doped biochars produced from urban wood residuals (particle board and compost overs). When raw (non N-doped) char from particle board was blended with Quincy sand soil at a rate of 10% by weight, water holding capacity more than doubled compared to no biochar, from 29.9 to 69.6 % by weight. However, N-doping provided little benefit compared to untreated (raw) biochar, and actually reduced the water holding capacity compared to raw biochar at higher application rates. Third generation biochars were produced by impregnating feedstock with metals (Mg, Ca, or Fe) and then using N-doping process to create a metal-N-doped biochar from both pure cellulose and wheat straw feedstocks. Metal-N doping using Mg and N together were effective at improving phosphate adsorption capacity for cellulose char to 335 mg g-1, and from wheat straw to 288 mg g-1. With further development, these processes hold great promise for integration into a municipal biorefinery. For example, activated biochar derived from AD fiber could be used for H2S removal from AD biogas and phosphate removal from AD effluent. Chars from could be sold and used to adsorb phosphate from a variety of other wastewaters or to reduce H2S emissions from compost. Within either of these scenarios, the resulting phosphate-charged biochar could perhaps be sold as a nutrient-rich soil amendment, though more information is needed to determine nutrient availability to plants following soil amendment with these materials.
Journal of environmental management, 2018
Different biochars produced by the impregnation of Mg, Ca, Al, Cu, and Fe were compared for the phosphate (P) uptake capacity and the effect on solution pH. Among them, Ca- and Mg-rich biochars demonstrate better sorption ability to P and have less effect on pH change. The optimum conditions of the pyrolysis processes were determined using response surface methodology. Comparison of the P removal efficiency of these two biochars under optimum conditions imply the superior adsorption capability of Ca-rich biochar. According to XRD analysis, calcite is the dominant mineral on the biochar surface, indicating the potential of Ca-rich biochar for P removal by adsorption and precipitation. Predictive second-order kinetic and linear Langmuir isotherm models could adequately interpret the P sorption process for optimized Ca-rich biochar. The maximum P sorption capacity of Ca-rich biochar of 153.85 mg/g is superior to other adsorbents reported in literature.
Sorption and desorption of phosphate on biochar and biochar–soil mixtures
The term biochar refers to materials with diverse chemical, physical and physicochemical characteristics that have potential as a soil amendment. The purpose of this study was to investigate the P sorption/desorption properties of various slow biochars and one fast pyrolysis biochar and to determine how a fast pyrolysis biochar influences these properties in a degraded tropical soil. The fast pyrolysis biochar was a mixture of three separate biochars: sawdust, elephant grass and sugar cane leaves. Three other biochars were made by slow pyrolysis from three Amazonian tree species (Lacre, Ing a and Emba uba) at three temperatures of formation (400°C, 500°C, 600°C). Inorganic P was added to develop sorption curves and then desorbed to develop desorption curves for all biochar situations. For the slow pyrolysis, the 600 ºC biochar had a reduced capacity to sorb P (4-10 times less) relative to those biochars formed at 400°C and 500°C. Conversely, biochar from Ing a desorbed the most P. The fast pyrolysis biochar, when mixed with degraded tropical mineral soil, decreased the soil's P sorption capacity by 55% presumably because of the high soluble, inorganic P prevalent in this biochar (909 mg P/kg of biochar). Phosphorus desorption from the fast pyrolysis biochar/soil mixture not only exhibited a common desorption curve but also buffered the soil solution at a value of ca. 0.2 mg/L. This study shows the diversity in P chemistry that can be expected when biochar is a soil amendment and suggests the potential to develop biochars with properties to meet specific objectives.
Iron and Magnesium Impregnation of Avocado Seed Biochar for Aqueous Phosphate Removal
Clean Technologies
There has been increasing interest in using biochar for nutrient removal from water, and its application for anionic nutrient removal such as in phosphate (PO43−) necessitates surface modifications of raw biochar. This study produced avocado seed biochar (AB), impregnated Fe- or Mg-(hydr)oxide onto biochar (post-pyrolysis), and tested their performance for aqueous phosphate removal. The Fe- or Mg-loaded biochar was prepared in either high (1:8 of biochar to metal salt in terms of mass ratio) or low (1:2) loading rates via the co-precipitation method. A total of 5 biochar materials (unmodified AB, AB + High Fe, AB + Low Fe, AB + High Mg, and AB + Low Mg) were characterized according to their selected physicochemical properties, and their phosphate adsorption performance was tested through pH effect and adsorption isotherm experiments. Fe-loaded AB contained Fe3O4, while Mg-loaded AB contained Mg(OH)2. The metal (hydr)oxide inclusion was higher in Fe-loaded AB. Mg-loaded AB showed a u...
Sustainability
The aim of this work was to compare the performance of biochar from various food processing wastes of different origin for the removal of different nutrients from water. Eggshells (EGS), rice husk (RH), and coffee biochars were pyrolyzed at 400 and 800 °C and were examined for the removal of phosphates, nitrates, and ammonia nitrogen. The raw materials were also modified with magnesium chloride in order to investigate their sorption behavior. The highest sorption capacity (qmax) for phosphates and ammonium was observed with EGS pyrolyzed at 800 °C and was 11.45 mg PO43−-P/g and 11.59 mg NH3-N/g, while the highest nitrates sorption capacity was observed with the magnesium-modified RH pyrolyzed at 800 °C (5.24 mg NO3−-N). The modified EGS biochars pyrolyzed at 800 °C had almost the half the sorption capacity for phosphates and nitrates compared to the unmodified materials. The modification of RH pyrolyzed at 800 °C resulted in higher sorption capacity by 34 and 158% for phosphates and...
Frontiers in Environmental Science, 2020
This study evaluated the potential of biochar impregnated with Fe3+ or Ca2+, or mixed with Polonite®, as a filter material for removal of phosphate (PO4-P) from wastewater in onsite wastewater treatment systems (OWTS). Four treatments with biochar were investigated: unimpregnated biochar (UBC), biochar impregnated with iron Fe3+ (FBC), biochar impregnated with calcium oxide (CBC), and biochar mixed with Polonite® (PBC). In a batch experiment using phosphate solution at concentrations 0.5, 3.3, 6.5, 13, and 26 mg PO4-P L–1, adsorption of PO4-P in the different treatments was modeled using Langmuir and Freundlich isotherms. Column filters (5 diameter × 55 cm height) packed with UBC, FBC, CBC, and PBC were then furnished with raw wastewater over 148 weeks. During this experiment, adsorption of PO4-P was investigated in response to increasing hydraulic loading rate (HLR; 56, 74, and 112 L m–2 day–1) and increasing phosphate loading rate (PLR; 195, 324, 653, and 1715 mg PO4-P m–2 day–1)....
Biochar
To improve the phosphorus (P) recovery efficiency from livestock wastewater, a novel MgO doped mildewed corn biochar with thermal pre-puffing treatment (Mg-PBC) and without pre-puffing (Mg-BC) was synthesized and tested. The thermal-puffing pretreatment improved the effectiveness of metal soaking and MgO dispersion. P recovery time with Mg-PBC (7 h) was significantly shorter than that with Mg-BC (12 h). Moreover, Mg-PBC showed significantly higher P recovery capacity (241 mg g−1) than Mg-BC (96.6 mg g−1). P recovery capacity of the Mg-PBC fitted to the Thomas model was 90.7 mg g−1, which was 4 times higher than that of Mg-BC (22.9 mg g−1) under column test conditions. The mechanisms involved in P recovery included precipitation, surface complexation, and electrostatic interaction. After adsorption, both Mg-BC and Mg-PBC showed relatively low regeneration abilities. The P loaded Mg-BC (Mg-BC-P) and Mg-PBC (Mg-PBC-P), the later particularly, obviously increased the available P content...