Biochar Mass Ratio Research Articles

Sustainable photodegradation of pharmaceuticals: KOH-impregnated palm oil mill effluent sludge biochar-BiOBr nanocomposite for wastewater treatment

Biochar has explored in the search of a cost-effective and environmentally friendly photocatalyst for the efficient degradation of CIP antibiotic pollutants. Biochar (BC) produced from palm oil mill sludge was used as a base to fabricate biochar-based BiOBr composites by varying the mass ratio of biochar and BiOBr via a hydrothermal route. The optimized composites BBC-1:1 has exhibited the formation of crystal struvture as tetragonal BiOBr with a a significant specific surface of 267 m2/g (BBC-1:1) while incorporating different mass ratios of BC with BiOBr. This composite facilitates the band gap of BiOBr from 2.87 to 2.42 eV and is consistent with the decreasing recombination rate of electron-hole pairs as suggested by UV-Vis DRS and photoluminescence (PL), respectively. Consequently, the synergistic effect of biochar BiOBr leads to a higher degradation efficiency of CIP showing the highest efficiency (97.49 %) and that of pure BiOBr being 55.66 % under optimized conditions. The degradation rate of the BBC-1:1 composite which observed to be 0.0156 min−1 is 3.25 times that of BiOBr (0.0048 min−1). Furthermore, the scavenging experiments confirmed the significant contribution of the active radicals h+ and O2- as the main photoactive species in the photocatalytic degradation of CIP. Consequently, the photocatalytic degradation mechanism was discussed and the reusability test confirmed the high stability of the BBC composites up to 77 % for the seventh cycles. These results show that the BBC composite is suitable for large-scale practical applications as a green photocatalyst.

Preparation of Cu/Cu2O/BC and Its Performance in Adsorption-Photocatalytic Degradation of Methyl Orange in Water.

In this study, we prepared a low-cost novel Cu/Cu2O/BC nanocomposite visible-light photocatalyst by the impregnation method using CuSO4·5H2O and rice husk biochar (BC) as raw materials and Na2S2O4 as a single reductant to improve the stability and dispersion of the Cu/Cu2O nanoparticles, in order to solve their aggregation tendency during photocatalysis. The morphology and structure of the Cu/Cu2O/BC were characterized using various analytical and spectroscopic techniques. The photocatalytic effect and cyclic stability of the synthesized photocatalyst on methyl orange (MO) removal were investigated under visible light radiation and various parameter conditions, including the mass ratio of BC to Cu/Cu2O, initial MO concentration, pH, temperature, and catalyst dosage. The results show that the synthesized Cu/Cu2O/BC nanocomposite composed of Cu/Cu2O spherical particles was loaded on the BC carrier, which has better stability and dispersion. The best adsorption-photocatalytic effect of the Cu/Cu2O/BC is exhibited when the mass ratio of BC to Cu/Cu2O is 0.2. A total of 100 mg of Cu/Cu2O/BC can remove 95% of the MO and 88.26% of the COD in the aqueous solution at pH = 6, T = 25 °C, and an initial MO concentration of 100 mg/L. After five cycles of degradation, the MO degradation rate in the sample can still remain at 78.41%. Both the quasi-secondary kinetic model and the Langmuir isothermal adsorption model describe the adsorption process. Additionally, the thermodynamic analysis demonstrates that the photocatalytic process follows the quasi-primary kinetic model and that the removal process is of spontaneous heat absorption. The photocatalyst described in this paper offers a cost-effective, easily prepared, and visible-light-responsive solution for water pollution treatment.

Regulating bacterial dynamics by Mg-modified biochar addition to mitigate gaseous emissions during pig manure composting

Gaseous emissions (i.e. Greenhouse gases (CH4 and N2O) and NH3) were a serious environmental problem during composting. Magnesium salt could effectively reduce NH3 emission with the principle of struvite crystallization. Biochar, particularly modified biochar, could be served as a new type of adsorbent for gaseous reduction. In this study, Mg-modified biochars were successfully prepared with different magnesium to biochar mass ratios, and then used as additives in pig manure composting. Mg-modified biochars exhibited excellent properties in terms of functional groups, porous structure and composition. Adding Mg-modified biochar improved composting performance, and thus synergistically reduced CH4, N2O and NH3 emissions. Especially, Mg-modified biochar prepared with the magnesium to biochar mass ratio of 0.50 (MBC-0.50) achieved the best reduction effects during pig manure composting. Both additive and composting phases could influence the bacterial composition by regulating temperature, pH, electrical conductivity and moisture content. Besides biochar adsorption, NH3 could be further reduced with the formation of struvite crystallization (MgNH4PO4·6H2O) by adding Mg-modified biochar. Pristine and modified biochars inhibited the proliferation of denitrifying bacteria (e.g. Pseudoxanthomonas and norank-f-Methylococcaceae) and anaerobe methanogenic bacteria (e.g. Jeotgalibaca and Lactobacillus) to further mitigate N2O and CH4 emissions. Results from this study provided unique insights to the development of Mg-modified biochar additive for mitigating CH4, N2O and NH3 emissions during composting.

Adsorption Characteristics and Mechanism of Ammonia Nitrogen in Water by Nano Zero-valent Iron-modified Biochar

The adsorption performances of ammonia nitrogen (NH+4-N) in water by unmodified biochar are ineffective. In this study, nano zero-valent iron-modified biochar (nZVI@BC) was prepared to remove NH+4-N from water. The NH+4-N adsorption characteristics of nZVI@BC were investigated through adsorption batch experiments. The composition and structure characteristics of nZVI@BC were analyzed using scanning electron microscopy, energy spectrum analysis, BET-N2 surface area (SSA), X-ray diffraction, and FTIR spectra to explore the main adsorption mechanism of NH+4-N by nZVI@BC. The results showed that the composite synthesized at the iron to biochar mass ratio of 1:30 (nZVI@BC1/30) performed well in NH+4-N adsorption at 298 K. The maximum adsorption amount of nZVI@BC1/30 at 298 K was remarkably increased by 45.96% and reached 16.60 mg·g-1. The pseudo-second-order model and Langmuir model fitted well with the adsorption process of NH+4-N by nZVI@BC1/30. There was competitive adsorption between coexisting cations and NH+4-N, and the sequence of coexisting cations to the adsorption of NH+4-N by nZVI@BC1/30 was Ca2+> Mg2+> K+> Na+. The adsorption mechanism of NH+4-N by nZVI@BC1/30 could be mainly attributed to ion exchange and hydrogen bonding. In conclusion, nano zero-valent iron-modified biochar can improve the adsorption performance of NH+4-N and enhance the application potential of biochar in the field of nitrogen removal from water.

Study on treatment of city tail water by constructed wetland with corn straw biochar substrate

Constructed wetland (CW) has obvious advantages in city tail water treatment. The biochar preparation from corn straw is an effective measure for improving the straw utilization. In order to improve the pollutant removal rate of CW, the city tail water treatment based on straw biochar substrate was studied. The thermogravimetric experiment of straw, characteristics test (scanning electron microscope, pore structure, element, adsorption) of biochar and city tail water treatment experiment by CW was carried out. The results show that the carbon fixation rate of straw biochar prepared at 450 °C (10 °C ⋅ min −1 , 2 h, N 2 ) was 67.72%, and the adsorption capacity of biochar exceeded 40% of the requirements of wood activated carbon adsorption standard. When the proportion of biochar in substrate was 2.95%, the mean removal rates of ammonia nitrogen, total nitrogen and nitrate nitrogen was more than 85%. This study will be conducive to reducing straw carbon emissions and improve CW technical level. • The carbon fixation rate of biochar prepared at 450 °C (10 °C ⋅ min −1 , 2 h,) was 67.72% • The adsorption of straw biochar for NH4+-N was greater than that of TP and NO3–N • Elovich equation was good to simulate the dynamic adsorption of NH4+-N, NO3–N and TP • The nitrogen removal rate was over 85% when the mass ratio of biochar was 2.95% in CW.

Pyrolysis and gasification integrated process of empty fruit bunch for multi-biofuels production: Technical and economic analyses

The use of renewable energy sources has been promoted with concern about limited fossil fuels and increased environmental impact. Empty fruit bunch (EFB), which is a valuable biomass residual from palm oil milling processes, is one of the most promising renewable energy sources that can be used to increase the monetary value of EFB through the pyrolysis and gasification integrated process for multi-biofuels production. This work aims to perform technical and economic analyses of the pyrolysis and gasification integrated process using EFB for multi-biofuels production. Firstly, the pyrolysis and gasification integrated process model is developed by using Aspen Plus simulator and employed to determine optimal conditions through a parametric analysis. Then, the design of a heat exchanger network is also incorporated to enhance the energy efficiency of the process using Aspen Energy Analyzer. Finally, the key economic performance indicators, i.e., payback period (PB), net present value (NPV), and internal rate of return (IRR), of the process are analyzed using Aspen Process Economic Analyzer. The results show that the integrated process should be operated at steam to biochar mass ratio of 2.7, gasifier temperature of 900 °C, steam to syngas mass ratio of 3.0, and WGS temperature of 240 °C to produce the maximum hydrogen, gases, gasoline, naphtha, kerosene and diesel at 140, 290, 657, 729, 298 and 811 kg h−1, respectively. Furthermore, in terms of heat integration, the minimum hot and cold utilities are required at 21,554 and 5,247 MJ h−1, respectively. The economic analysis results indicate that the proposed process is economically feasible and attractive with 5.98 years of PB, $ 249,951,964 of NPV, and 22% of IRR.

Removal of gaseous H2S using microalgae porous carbons synthesized by thermal/microwave KOH activation

H2S has strong toxicity and corrosivity, which can endanger human health and corrode equipment. This article used the two types of activation methods as a comparison to activate raw biochar from microalgae pyrolysis to prepare microalgae porous carbon for removal of gaseous H2S. The difference in textural properties and functional group of the prepared microalgae porous carbon using two types of activation methods is studied emphatically. Then physicochemical property of microalgae porous carbons was characterized and effect of activation methods, KOH/raw biochar mass ratio and sorption temperature on desulfurization was tested. Sorption products, mechanism, kinetics and thermodynamics were studied. Reuse of deactivated adsorbents was also explored. Research revealed that both activation methods substantively improved pore structure and increased active functional group contents of raw biochar, greatly promoting desulfurization. Compared to thermal activation, active functional groups of microalgae porous carbons prepared by microwave-assisted activation had no obvious difference, but pore structure was greatly improved, leading to higher H2S sorption capacity. Results of product characterization, thermodynamics and kinetics demonstrated that in the H2S sorption process, physical sorption was major and chemical sorption was auxiliary. Spent containing-sulfur microalgae porous carbons showed good Hg0 capture ability, far exceeding commercial activated carbon.

Preparation of Bamboo-Based Hierarchical Porous Carbon Modulated by FeCl3 towards Efficient Copper Adsorption.

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe3+ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K2CO3 impregnation ratio, activation temperature, and Fe3+ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC 2.5-900-2%, impregnated at a K2CO3: biochar ratio of 2.5 and a Fe3+: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N2 atmosphere, has a very high specific surface area of 1996 m2 g−1 with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g−1 and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water.

Performance and mechanism of a biochar-based Ca-La composite for the adsorption of phosphate from water

In this study, a calcium-modified biochar with a high dephosphorization efficiency was obtained using sheep manure as a carbon source and oyster shells as a calcium(Ca) source. However, it was found that the calcium-modified biochar had a low-pH inadaptability. Based on this, lanthanum(La) was doped in place of Ca to prepare biochar with a strong phosphate adsorption ability in a wide range of pH. The results showed that with the increase of Ca content, the phosphorus adsorption capacity of the material with a mass ratio of biochar to oyster shells of 1:1 (BC-Ca5) increased gradually, and the maximum adsorption capacity that was fitted by the Langmuir equation reached 78.11 mg P/g. Also, the adsorption capacity was 48.70 mg P/g when the pH > 7, and lower than 6 mg P/g when pH ≤ 7. The maximum adsorption capacity fitted to the Langmuir equation of the material with a mass ratio of biochar, oyster shells, and La of 1:1(BC-La4) reached 88.34 mg P/g, and the adsorption capacity reached 50 mg P/g under all pH conditions except pH = 7. Ca was mostly found on the surface of the biochar, and La was mainly present in the internal pore structure. The FTIR, XRD, and XPS results showed that the main adsorption mechanism was complexation. This study provides a reference for the resource utilization of livestock and poultry manure and shell solid wastes, as well as metal sources for metal modified biochar, and improving the adsorption performance of calcium-modified biochar.

Synthesis of nZVI-Ni@BC composite as a stable catalyst to activate persulfate: Trichloroethylene degradation and insight mechanism

In Fenton-like oxidation processes, the use of biochar (BC) as support material for the nanoscale zero valent iron-nickel (nZVI-Ni) bimetallic particles attained much attention to activate persulfate (PS) for TCE degradation in aqueous medium. In present work, nZVI-Ni@BC particles with nZVI-Ni to BC mass ratio of 1:5 exhibited excellent results (> 99 % ± 0.24) for TCE degradation. The physico-chemical characteristics, surface morphologies, and elemental mapping of the synthesized nZVI-Ni@BC particles investigated through SEM, EDX, TEM, XPS, XRD, BET and FTIR spectroscopy. For the nZVI-Ni@BC-persulfate system, the effects of PS concentration, initial pH, inorganic ions and natural organic matter (NOM) on TCE degradation were evaluated. Batch experiments revealed that complete removal of TCE (> 99 % ± 0.25) was attained at 250 mg L−1 of nZVI-Ni@BC and 4.0 mM PS dosages at pH 3.49 ± 0.55. Scavenging and electron paramagnetic resonance (EPR) verified the dominant role of both SO4ˉ and OH radicals in acidic environment for degradation of TCE. Moreover, high level of carbonate, bicarbonates and NOM inhibited the overall TCE oxidation reaction. In summary, these results suggested that nZVI-NI@BC composite was an alternative, economic and promising catalyst for the activation of PS to degrade chlorinated contaminants in aqueous medium.

Enhanced Sorption of Cetirizine to Loessial Soil Amended with Biochar

Biochar could be used as a stabilizer to control the migration and transformation of pollutants in soil and reduce their environmental risks. Cetirizine (CTZ) was selected as a target pollutant to investigate the effect of biochar on sorption characteristics of loessial soil by batch experiments. Biochars were produced from walnut shell at different temperatures and added to soil at different mass ratios. The results indicated that all biochars showed obviously higher sorption capacity than loessial soil. The sorption capacity for CTZ was obviously enhanced by soils amended with biochars produced at 400-700℃, which could be attributed to the increased bulk carbon content and specific surface area (SA). Sorption of CTZ to mixtures, excluding the soils amended with biochar produced at 300℃, was lower than the theoretical value. This could be due to the cross-effect between soil components and biochar. At the same time, the organic matter and native sorbates in soil may block or compete for adsorption sites on biochar surface. Biochars would be helpful to stabilize the loessial soil contaminated with CTZ. However, for relatively low concentration of CTZ in aqueous solution and soils amended with relatively high biochar mass ratio, the sorption capacity of the mixtures could be overestimated theoretically without considering the cross-effect between soil and biochar.

Removal of Pb2+ using a biochar–alginate capsule in aqueous solution and capsule regeneration

A biochar–alginate capsule (BAC) was successfully synthesized by dropping a mixture solution of biochar (BC) and calcium chloride (CaCl2) into an alginate (AG) solution, with adjusting the mass ratio of BC to AG. The adsorption characteristics of the BAC were investigated by measuring the removal of lead ions (Pb2+) from an aqueous solution. The maximum adsorption of Pb2+ was found at a pH of 5.0 and an adsorption time of 120 min. The lead adsorption equilibrium data of the BAC fit well with the Langmuir and Freundlich equations. Based on the Langmuir isotherm, which was a better fit than the Freundlich isotherm, the maximum sorption capacity of Pb2+ by BAC (BC:AG = 8:1) was 263.158 mg/g, which is much higher than the capacity for other adsorbents. The sorption adequately followed the pseudo second-order kinetic expression (R2 = 0.997). The BAC was easily collected after the Pb2+ adsorption process and highly recoverable (90–95%) using a HNO3 solution. The adsorption efficiency of Pb2+ by the recovered BAC remained around 70% of the initial adsorption capacity even after being recycled 10 times (repeated adsorption–desorption).

Biochar As a Precursor of Activated Carbon

Biochar was evaluated as a precursor of activated carbon. This product was produced by chemical activation using potassium hydroxide. The effects of operating conditions of activation process, such as temperature, activating agent to biochar mass ratio, and nitrogen flow rate, on the textural and chemical properties of the product were investigated. Activated carbon produced by this method has internal surface area at least 50 times than that of the precursor and is highly microporous, which is also confirmed by scanning electron microscopy analysis. Fourier-transform infrared spectroscopy analysis showed development of aromatization in the structure of activated carbon. X-ray diffraction data indicated the formation of small, two-dimensional graphite-like structure at high temperatures. Thermogravimetric study showed that when potassium hydroxide to biochar mass ratio was more than one, the weight loss decreased.