Calcium-rich biochars (CRB) prepared through pyrolysis of crab shell at various temperatures were characterized for physicochemical properties and P removal potential. Elemental analysis showed that ...CRB was rich in calcium (22.91%–36.14%), while poor in carbon (25.21%–9.08%). FTIR, XRD and TG analyses showed that calcite-based CRB was prepared at temperature ≤600 °C, while lime-based CRB was prepared at temperature ≥700 °C. Phosphorus removal experiment showed that P removal efficiencies in 80 mg P/L phosphate solution and biogas effluent ranged from 26% to 11%, respectively, to about 100% and 63%, respectively, depending on the pyrolysis temperature of the resulting biochar. Specifically, compared to common used CaCO3 and Ca(OH)2, P removal potential of calcite-based CRB was much higher than that of CaCO3; while that of lime-based CRB was close to that of Ca(OH)2. These results suggested that CRB was competent for P removal/recovery from wastewater.
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•Calcium-rich biochar (CRB) for phosphorus removal was prepared from crab shell.•Calcite-based CRB was prepared at temperature ≤600 °C.•Lime-based CRB was prepared at temperature ≥700 °C.•Calcite-based CRB showed higher phosphorus removal potential than CaCO3.•Phosphorus removal potential of lime-based CRB was close to that of Ca(OH)2.
The surplus of manure phosphorus (P) with increasing livestock production might pose a risk of P loss to the environment due to the high mobility of P in manure. Thus, there is an increasing need to ...mitigate P loss from manure. This study aimed to investigate the effect of hydrothermal carbonization (HTC) on the immobilization of P in cow manure. The results demonstrated that the P content in cow manure was increased substantially by ∼20% after HTC, while the water-extractable P (WEP) and Mehlich-3-extractable P (MEP) in manure was reduced significantly by >80% and 50%, respectively. The decrease in P solubility might result from the increased apatite P (increased by >85%) and decreased soluble Ca (decreased by ∼50%) after HTC. These results suggested that HTC could be an efficient strategy to immobilize P in cow manure, thereby potentially mitigating the P loss problem from cow manure.
•Cow manure (85% moisture) was directly treated by hydrothermal carbonization (HTC).•The water extractable phosphorus (P) in manure was reduced by >80% during HTC.•The Mehlich-3 extractable P in manure was reduced by >50% during HTC.•The decreased P mobility was attributed to the formation of apatite P during HTC.
The effect of simultaneously removing algal blooms from water and reducing the resuspension and nutrient release from the sediment was studied using modified local soil/sand flocculation-capping ...(MLS-capping) in simulated water-sediment systems. Twenty one sediment cores in situ with overlying water containing algal blooms were collected from Meiliang Bay of Lake Taihu (China) in July 2011. The algal cells in the water were flocculated and sunk to the sediment using chitosan modified local soils, and the algal flocs were capped with modified and nonmodified soil/sand and then incubated at 25 °C for 20 days. In the MLS-capping treated systems, the TP concentration was reduced from 2.56 mg P L–1 to 0.06–0.14 mg P L–1 and TN from 14.66 mg N L–1 to 6.03–9.56 mg N L–1 throughout the experiment, whereas the sediment to water fluxes of TP, TN, PO4–P, and NH4–N were greatly reduced or reversed and the redox potential remarkably increased compared to the control system. A capping layer of 1 cm chitosan-modified sand decreased the resuspension of the sediment by a factor of 5 compared to the clay/soil/sediment systems and the overlying water kept clear even under constant stirring conditions (200 rpm). The study suggested that by using MLS-capping technology it is possible to quickly reduce the nutrient and turbidity of water by flocculating and capping the algal cells into the sediment, where the resuspension of algal flocs is physically reduced and the diffusion of nutrients from sediment to the overlying water chemically blocked by the MLS capping layers.
•Lanthanum doped hydrochar was prepared by one-pot hydrothermal carbonization.•The adsorbents was highly effective in P adsorption in a wide range of pH.•The competing anions showed little negative ...effects on P adsorption on the adsorbent.
Engineered hydrochar composites (EHC) were synthesized by hydrothermal carbonization (HTC) of lanthanum pretreated rice straw. The as-prepared composite with about 30% lanthanum content showed greater P removal potential than La(OH)3, indicating the synergistic effect of hydrochar and lanthanum in P removal. The adsorption results showed that EHC showed great P adsorption capacities (>50mgPg−1) in the pH range of 2.5–10.5, and the presence of competing anions had little negative effects on P adsorption on EHC. The equilibrium time for P adsorption on EHC was considerably reduced under acid condition (12h) compared to alkaline condition (48h). The maximum adsorption capacity was 61.57mgPg−1 according to Langmuir isotherms. These results suggested that EHC was highly effective in P adsorption in a wide range of pH and the presence of competing anions, thus EHC could be a promising adsorbent for phosphorus removal/recovery from wastewater.
A natural red soil and a lanthanum-modified soil (LMS) were tested to compare their phosphorus (P) adsorption capacities and their effectiveness in removing P from the water column and reducing P ...release from sediment. The equilibrium of P adsorption demonstrated that the maximum P adsorption for the soil was 1.29 and 2.22 mg g(-1) at pH 8.5 and 5.5, respectively, and for the LMS these were increased by 45.6 and 77.6% at pH 8.5 and 5.5, respectively, indicating that the soil was effective in P adsorption and the doping of lanthanum could substantially increase P adsorption. The sediment-water column incubation showed that, due to the P adsorption of the soil and LMS, the total P in the water column decreased by 58.5, 60.6, 68.2 and 77.2% for 180 g m(-2) soil, 900 g m(-2) soil, 180 g m(-2) LMS and 900 g m(-2) LMS treated systems, respectively, in a short time (6 h), and the capping layer substantially reduced the P release from sediment during column incubation, indicating that the soils were effective in reducing internal P load. However, considering the cost of LMS, the natural soil was suggested to be a cost-effective material to control internal P load.
Phosphorus (P) in water and sediment in the Yellow River was measured for 21 stations from the source to the Bohai Sea in 2006–2007. The average total particulate matter (TPM) increased from 40 mg/L ...(upper reaches) to 520 mg/L (middle reaches) and 950 mg/L in the lower reaches of the river. The average dissolved PO4 concentration (0.43 μmol/L) was significantly higher than that in 1980’s but lower than the world average level despite high nutrient input to the system. Much of the P input was removed by adsorption, which was due to the high TPM rather than the surface activity of the particles since they had low labile Fe and low affinity for P. The sediment was a sink for P in the middle to lower reaches but not in the upper to middle reaches. TPM has been reduced by more than an order of magnitude due to artificial dams operating over recent decades. Modeling revealed that TPM of 0.2–1 g/L was a critical threshold for the Yellow River, below which most of the phosphate input cannot be removed by the particles and may cause eutrophication. These findings are important for river management and land–ocean modeling of global biogeochemical P cycling.
In this work, a modification method of H3PO4 plus H2O2 (PHP) was introduced to targetedly form abundant oxygenated functional groups (OFGs) on biochar, and methylene blue (MB) was employed as a model ...pollutant for adsorption to reflect the modification performance. Results indicated that parent biochars, especially derived from lower temperatures, substantially underwent oxidative modification by PHP, and OFGs were targetedly produced. Correspondingly, approximately 21.5-fold MB adsorption capacity was achieved by PHP-modified biochar comparing with its parent biochar. To evaluate the compatibility of PHP-modification, coefficient of variation (CV) based on MB adsorption capacity by the biochar from various precursors was calculated, in which the CV of PHP-modified biochars was 0.0038 comparing to 0.64 of the corresponding parent biochars. These results suggested that the PHP method displayed the excellent feedstock compatibility on biochar modification. The maximum MB adsorption capacity was 454.1 mg/g when the H3PO4 and H2O2 fraction in PHP were 65.2% and 7.0%; the modification was further intensified by promoting temperature and duration. Besides, average 94.5% H3PO4 was recovered after 10-batch modification, implying 1.0 kg H3PO4 (85%) in PHP can maximally modify 2.37 kg biochar. Overall, this work offered a novel method to tailor biochar towards OFGs-rich surface for efficient adsorption.
H3PO4 plus H2O2 (PHP) was introduced to targetedly modify biochar for rich-OFGs surface; the adsorption of model pollutant (methylene blue) using the PHP-modified biochar can be significantly promoted by 21.5 folds comparing with the corresponding parent biochar. Display omitted
•Upcycling waste gas to H2 for a carbon-neutral circular economy.•249.14 M tons of industrial CO could yield ∼17.44 M tons of H2 yearly.•H2 from waste industrial gases could contribute in achieving ...SDG 7, 9 & 13.
Industrial sectors, pivotal for the economic prosperity of nations, rely heavily on affordable, reliable, and environmentally friendly energy sources. Industries like iron and steel, oil refineries, and coal-fired power plants, while instrumental to national economies, are also the most significant contributors to waste gases that contain substantial volumes of carbon monoxide (CO). CO can be converted to a highly efficient and carbon free fuel, hydrogen (H2) through a well-known water gas shift reaction. However, the untapped potential of H2 from waste industrial streams is yet to be explored. This is the first article that investigates the potential of H2 production from industrial waste gases. The available resource (i.e., CO) and its H2 production potential are estimated. The article also provides insights into the principal challenges and potential avenues for long-term adoption. The results showed that 249.14 MTPY of CO are available to produce 17.44 MTPY of H2 annually. This suggests a significant potential for H2 production from waste gases to revolutionize industrial waste management and contribute significantly towards Sustainable Development Goals 7, 9, and 13ensuring access to affordable, reliable, sustainable, and modern energy for all and taking decisive climate action, respectively.
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Biochar has attracted increasing attention in water pollution control, attributed to its various merits, e.g., tunable physico-chemical properties. The oxygenated functional groups (OFGs) on biochar ...are key active sites for removing pollutants from water through interfacial adsorption/redox reaction. However, there is still a lack of comprehensive knowledge and perspective on tuning OFGs on biochar for enhanced performance in water pollution control. Here, this review highlighted the mechanisms of biochar OFGs in water pollution control, analyzed the strategies and mechanisms for tuning OFGs on biochar, and investigated the performances of biochars with tuned OFGs in removing inorganic/organic pollutants via adsorption/redox reactions. Specifically, strategies for tuning OFGs on biochar are far more than the well-recognized ex-situ oxidation of pristine biochar. These strategies include in-situ low temperature preservation of hydroxyl and carboxyl, in-/ex-situ oxidation of biochar, and in-/ex-situ grafting of carboxyl on biochar via cycloaddition/acylation reaction. The resultant biochars showed enhanced performances in adsorption (mainly mediated by hydroxyl, carboxyl and ketone through surface complexation, H-bonding, and electrostatic attraction) and redox reaction (mainly mediated by redox-active hydroxyl and ketone). Finally, this review presented future directions on developing biochar with specially tuned surface OFGs as a sustainable high-performance adsorbent/carbocatalyst for water pollution control.
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•Functions of oxygenated functional groups (OFGs) on biochar are summarized.•Strategies for tuning OFGs on biochars are systematically reviewed.•Knowledge gaps on tuning OFGs on biochar for enhanced performances were proposed.•Tuning OFGs on biochar favors its application in adsorption/redox reactions.
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•Calcium-rich biochar is derived from naturally available crustacean biomass.•Unique multi-layered structure makes CRB possess amazing removal capacity.•Removal capacity of CTC by ...adsorption coupling with flocculation is 5048.0 mg g−1.•Calcium-rich biochar is promising in emergency treatment of CTC wastewater.•Multiple interactions were involved in removal process depending on C0-CTC.
A high residual concentration of antibiotics in the environment represents a to the animal and human health, thus, removal of these antibiotics is an urgent problem in need of a solution. In this study, calcium-rich biochar (CRB) pyrolyzed from a natural organic-inorganic-composite (i.e., crab shell) was investigated for its significant efficiency in removing efficiency of chlortetracycline (CTC) from aqueous solution. Batch experiments were conducted to explore the interaction between CRB and CTC to characterize the ability of CRB to remove CTC. Results showed that the equilibrium pH of the system decreased as the initial concentration of CTC increased, resulting in a complicated CTC removal process. Specifically, at a low initial concentration of CTC, the predominantly occurred through adsorption, which is well-described by the Freundlich isotherm model. The adsorption capacity of CRB for CTC reached 1432.3 mg g−1 at 298 K. Adsorption rates were estimated by kinetic models, and the pseudo-second-order model displays a good fit for the kinetic data at various concentrations. Adsorption and flocculation were responsible for the removal of CTC at a high initial concentration. The maximum removal capacity was 5048 mg g−1 at 298 K. Microcosmic characterization and macroscopic results demonstrated that cation bridging, π-π interaction, electrostatic interaction and hydrogen bonding could be involved in the removal process, which varied with the initial concentration of CTC. Therefore, based on the high-efficiency and low-cost of CRB, this material promises to be an ideal candidate to remove antibiotics (e.g., CTC) from wastewater and control their transport within the environment.
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