Search Results (32)

Although metal-modified biochar demonstrates high efficacy for phosphorus (P) removal in aqueous systems, its soil-scale mechanisms and ecological consequences under extreme rainfall remain largely unknown. In this study, we investigated how iron-modified biochar (BC+Fe) regulates P leaching and soil microbial communities in acidic soils using adsorption assays and column leaching experiments under simulated prolonged heavy rainfall. Mechanistically, BC+Fe exhibited adsorption kinetics that were better described by the pseudo-second-order model, consistent with a chemisorption-dominated P retention mechanism. Across six consecutive leaching events, BC+Fe significantly increased soil pH from 4.1 to 4.5 and reduced cumulative P loss by 37.7% compared to unmodified biochar (BC), with the most pronounced mitigation occurring during the initial leaching events when P losses were greatest. After leaching, soil total and available P concentrations under BC+Fe were approximately 3.4- and 3.7-fold higher, respectively, than under BC. Crucially, while both biochar types shifted bacterial community composition, BC+Fe maintained bacterial Shannon diversity and network complexity at levels comparable to the unamended soil and significantly higher than those under BC. Further analysis revealed that P leaching loss and soil pH were the primary environmental drivers shaping these microbial responses, and specifically, severe P loss was directly associated with simplified network complexity and intensified microbial competition (reflected by increased negative cohesion). Functional profiles inferred using Tax4Fun2 further showed that BC+Fe supported higher predicted microbial functional redundancy than both BC and the unamended control. Collectively, these findings demonstrate that iron-modified biochar mitigates P leaching through robust chemisorption and pH stabilization, while concurrently safeguarding microbial network complexity and functional redundancy. This dual benefit highlights the potential of iron-modified biochar as a sustainable amendment for maintaining soil ecosystem buffering capacity against severe hydrological stress. Full article

To address the ecological risks associated with highly mobile hexavalent chromium [Cr(VI)], woody biochar was functionalized with hydrogen peroxide (H₂O₂) to develop a dual-phase remediation material (H-BC) for aqueous and soil environments. Batch post-contact isotherm fitting yielded a Langmuir-fitted/extrapolated apparent retention capacity q_m of 77.44 mg/g at 328 K. This value reflects enhanced overall Cr(VI)-derived retention within the tested concentration range, rather than increased electrostatic affinity for chromate oxyanions. Empirical kinetic diagnostics and FTIR/XPS results were consistent with adsorption-coupled interfacial reduction, while DFT analysis provided qualitative support for the enhanced electronic responsiveness of H-BC. The OFG-enriched interface may facilitate short-range, non-electrostatic interfacial interactions and stabilize surface-associated Cr(III). Temperature-dependent apparent isotherm fitting suggested that elevated temperature favored the overall Cr(VI)-derived retention process under the tested conditions, and should not be interpreted as rigorous standard-state adsorption thermodynamics. Continuous-flow column leaching and accelerated wet–dry (W–D) aging experiments demonstrated that H-BC substantially suppressed the mobility of operationally filtered Cr(VI), achieving a maximum filtered-Cr(VI)-based retention efficiency of 99.98% under cyclic drying–rewetting conditions. Spatial configuration analysis indicated that homogeneous incorporation of H-BC improved soil–biochar contact and was more effective than stratified placement in limiting vertical filtered-Cr(VI) migration. Overall, oxidatively functionalized H-BC shows promise as a biomass-derived amendment for reducing Cr(VI) mobility in complex environmental matrices, although complete chromium mass redistribution will require future total-Cr and Cr(III)-resolved analyses. Full article

Rapid dissolution of conventional fertilizers causes low nutrient-use efficiency and serious leaching losses, contributing to agricultural non-point source pollution. In this study, biomass-based slow-release fertilizer beads were prepared by ionic crosslinking of potato starch (ST), chitosan (CS), and corn-straw biochar (BC), using potassium nitrate (KNO₃) as the model nutrient. The effects of ST/CS ratio and BC incorporation on bead structure, swelling, nutrient loading, release kinetics, and soil-column leaching were systematically investigated. Biochar incorporation formed a more compact and interconnected porous network and reduced the equilibrium swelling ratios of ST90/CS10, ST80/CS20, and ST70/CS30 from 188%, 176%, and 164% to 168%, 136%, and 104%, respectively. Although BC slightly decreased KNO₃ loading capacity, it markedly slowed nutrient release; ST80/CS20/BC20 released 31.09%, 50.09%, and 81.82% of loaded KNO₃ at 24, 72, and 504 h, respectively, which were 28.40%, 25.27%, and 11.30% lower than those of ST80/CS20. Kinetic fitting indicated that BC reduced the apparent release rate and promoted diffusion-controlled release behavior. Soil-column experiments further showed that the beads reduced NO₃⁻-N and K⁺ leaching compared with free KNO₃, with ST80/CS20/BC20 showing the best balance between nutrient loading and release control. These results suggest that starch–chitosan–biochar beads are a promising biodegradable matrix for slow-release fertilizer applications. Full article

Efficient uranium recovery from productive leaching solutions requires accurate prediction of hydrodynamic and mass-transfer processes in ion-exchange sorption columns. In this study, a coupled multidimensional hydrodynamic and mass-transfer model is developed to investigate uranium sorption in a packed ion-exchange column equipped with a conical flow distributor. Fluid flow in the porous resin bed is described using the Forchheimer filtration law combined with the mass conservation equation, while transport of dissolved uranium species is modeled using a convective–dispersion equation coupled with a linear driving force kinetic model. The numerical solution is obtained using the fictitious domain method, which enables accurate representation of complex column geometries. The results reveal pronounced radial flow non-uniformity, incomplete flow equalization, and the formation of a ring-shaped sorption zone, indicating uneven utilization of the sorbent bed. It is shown that under practical operating conditions, mass-transfer dynamics are governed primarily by hydrodynamics rather than intrinsic sorption kinetics. The proposed model provides a practical tool for analysis and optimization of industrial uranium recovery columns. Full article

Acid mine drainage (AMD), wherein acidic water is generated from pyrite-containing waste rock, can be mitigated by encapsulating pyritic waste rock with cover materials to restrict the inflow of oxygen and water. However, acidic water inevitably forms during the construction of waste rock dumps before applying cover materials. Considering that the presence of waste rock containing carbonate minerals contributes to acid neutralization, a mixture of carbonate minerals and pyritic waste rock can be utilized to reduce AMD generation before the completion of the cover system as a temporary management strategy. This paper examines waste rock management using blending scenarios. Kinetic NAG and column leaching tests were employed to evaluate the blending ratio necessary to prevent acidic water generation. Geochemical analyses were conducted on rock and leachate samples, including pH and temperature measurements, XRD and XRF analyses, and Ion Chromatography. Consequently, the pH and temperature measurement results obtained during the kinetic NAG test are valuable for expressing the balance between acid generation and acid neutralization by the mixture material. Furthermore, the column leaching test demonstrated that the pH of the leachate remained neutral when the acid generation and acid neutralization reactions were well balanced. Blending waste rocks is an effective method for AMD reduction during the construction of waste rock dumps. Full article

This paper studies the process mineralogy, mechanism, and kinetics of column leaching behavior of low-grade high-calcium–magnesium copper ore. The effect of sulfuric acid concentration, leach solution spraying intensity, and material particle size on column leaching kinetics is discussed. The kinetic analysis of column leaching of copper indicates that sulfuric acid concentration has a significant impact. As sulfuric acid concentration increases, the limiting step of reaction shifts from chemical reaction control to a combination of chemical reaction and diffusion mixing control. Spraying intensity also affects copper column leaching; increasing intensity shifts the limiting step from diffusion control to mixing control, thereby mitigating the effects of diffusion control. Regarding other elements, it is found that iron leaching is primarily controlled by chemical reaction, while calcium leaching is mainly controlled by chemical reaction. As sulfuric acid concentration increases from 10 g/L to 20 g/L, the limiting step for calcium leaching shifts from chemical reaction control to chemical reaction and diffusion-mixing control. Full article

This study introduces a straightforward and effective amorphous ZrP/polyacrylonitrile composite ion exchange method for separating Li from the leachate of spent Li-ion batteries (NMC 111). The cathode materials were leached with a series of optimized experiments. The influence of operating variables, including the H₂SO₄ concentration, temperature, H₂O₂ concentration, and pulp density, on leaching efficiency was examined to determine the optimal conditions for sorption experiments. The leaching efficiencies of Li, Co, Ni, and Mn were found to be 99.9%, 99.5%, 98.8%, and 99.9%, respectively. Subsequently, batch sorption experiments were performed by using am-ZrP/PAN, including the determination of the effect of pH, sorption kinetics, and the sorption isotherm. The effect of pH on adsorption was examined in 1 mmol/L equimolar solutions of Li, Ni, Mn, and Co. Li was separated from Mn, Co, and Ni in the leaching liquor. The adsorbent for Mn, Co, and Ni sorption better fitted pseudo-second-order kinetics. High selectivity for Li was observed, even at the higher solution concentration of 15 mM Li, Ni, Co and Mn. In addition, the column loading process demonstrated selectivity for Li over Co, Ni, and Mn metal ions. The preliminary evaluation of the whole process with mass flow demonstrated that it would be feasible to achieve full separation and metal recovery by integrating a combined hydrometallurgical method in future studies. However, much work is still needed to develop a practical separation flowsheet. Full article

Mathematical modeling of columnar leaching is a useful tool for predicting and evaluating the kinetics of copper extraction. One commonly used model for this process is the shrinking core model (SCM). In this study, the aim was to develop a model for column leaching of oxidized copper ore based on the SCM, which incorporates the ore sulfation stage before leaching. In sulfation and leaching laboratory-scale tests, we studied the effect of acid dosage (at 22.8, 34.2, and 45.6 kg/t), humidity (at 90%, 100%, and 110% of the saturation humidity of the mineral), ore granulometry (−3/4″ and −3/8″), and rest time (at 24, 48, 72, and 96 h) on sulfation. We found that the highest sulfation reached 49.7% for both granulometries in studies. In the column tests, the effects of acid dosage (at 34.2, 45.6 kg/t), ore granulometry (−3/4″, −3/8″), and rest time (at 24, 48 h) were studied. When the SCM was applied to these tests, we obtained fit qualities within 63.4% and 74.9%. By incorporating the sulfation factor into the SCM predictions, we observed an average increase in adjustment between 24% and 28%. This method is effective for minerals and operating conditions different from the ones studied. Full article

A large amount of ammonium salt leaching agent will remain in the leaching site of weathered crust elution-deposited rare earth ore (WREOs). The release of residual ammonium (RA) will seriously affect the water system ecology of the mining area, and it is urgent to control it. In this paper, column eluting was used to simulate the eluting process of RA in rare earth (RE) ore tailings, and the effects of calcium chloride concentration, eluting temperature, liquid-solid ratio, eluent pH and eluent flow rate on the eluting process of RA in rare earth ore tailings were discussed. It was found that calcium chloride could effectively elute the RA from ore tailings. Eluting agent pH almost had no effect on the eluting process of RA in the pH range of 4–6, and a greater impact on it at pH 8. The flow rate could effectively enhance the elution efficiency. The optimum conditions were calcium ion concentration of 0.1 mol/L, liquid-solid ratio of 2:1, pH 4–6, flow rate of 0.6 mL/min and elution at room temperature. At this time, the elution efficiency of RA was 91.85%. The eluting process of RA in ore tailings was controlled by the inner particle diffusing according to the kinetic analysis. The reaction order was 0.368, and the activation energy of the reaction is 12.450 kJ/mol. This will provide a theoretical basis and technical support for the efficient eluting process of residual ammonium in the leaching site of WREOs. Full article

Heavy metal contamination in drinking water is a growing concern due to its severe health effects on humans. Among the many metals, lead (Pb), which is a toxic and harmful element, has the most widespread global distribution. Pb pollution is a major problem of water pollution in developing countries and nations. The most common sources of lead in drinking water are lead pipes, faucets, and plumbing fixtures. Adsorption is the most efficient method for metal removal, and activated carbon has been used widely in many applications as an effective adsorbent, but its high production costs have created the necessity for a low-cost alternative adsorbent. Biochar can be a cost-effective substitute for activated carbon in lead adsorption because of its porous structure, irregular surface, high surface-to-volume ratio, and presence of oxygenated functional groups. Extensive research has explored the remarkable potential of biochar in adsorbing Pb from water and wastewater through batch and column studies. Despite its efficacy in Pb removal, several challenges hinder the real application of biochar as an adsorbent. These challenges include variability in the adsorption capacity due to the diverse range of biomass feedstocks, production processes, pH dependence, potential desorption, or a leaching of Pb from the biochar back into the solution; the regeneration and reutilization of spent biochar; and a lack of studies on scalability issues for its application as an adsorbent. This manuscript aims to review the last ten years of research, highlighting the opportunities and engineering challenges associated with using biochar for Pb removal from water. Biochar production and activation methods, kinetics, adsorption isotherms, mechanisms, regeneration, and adsorption capacities with process conditions are discussed. The objective is to provide a comprehensive resource that can guide future researchers and practitioners in addressing engineering challenges. Full article

Although the importance of black copper ores is well established, many topics remain to be studied. This manuscript describes the efforts to improve copper recovery from refractory ores on a pilot scale. Preliminary tests provided the water dose to form a stable and compact agglomerate of 89 L per ton of ore and an acid dosage of 40 kg per ton of ore. The column leaching method resulted in an effluent with 1.63 g/L Cu, a pH of 1.04, and a redox potential of 675 mV (average). Despite the similarities observed in the results, reductant agents were essential to dissolve the MnO₄ present in the black copper ore. Thus, the best Mn extraction results were 67.7% using the MnO₂:FeSO₄ ratio of 1:3. Additionally, the kinetics of leaching are slower than in an industrial operation. The copper ore under study required more than 65 days of leaching to reach the maximum copper recovery. Finally, the total recovery of copper (including washing and resting time) indicates that the maximum value was reached for ore pretreated with NaCl, H₂SO₄, and FeSO₄, concluding that the use of agents favored leaching. Full article

Recovery of metals from e-waste forms a major focus of circular economy thinking and aligns well with the Sustainable Development Goals (SDG). While hydrometallurgical extraction from electronic printed circuit boards (PCBs) is well established, the separation of metals from the leach liquors, which are complex mixtures, remains a challenge. To achieve selective separation, ion exchange resins with chelating functional groups were employed in the present study. Batch and column studies for selective recovery of Cu²⁺ from a given mixed metals leach solution were conducted using Dowex M4195 resin, and both the adsorption isotherm and kinetics were studied. The process involves three major steps: selective recovery of Cu²⁺ by M4195 at low pH and elution with H₂SO₄; sorption of Ni²⁺ from the raffinate by Dowex M4195 at pH 2 and removal of Fe³⁺ from raffinate. The batch experimental results showed appreciable and selective recovery of copper (51.1%) at pH 0.7 and 40.0% Ni²⁺ was sorbed from raffinate at pH 2.0 with co-adsorption of Fe³⁺ as impurity. The batch adsorption data could be fitted with both Langmuir and Freundlich isotherms and exhibited pseudo-second-order kinetics. Column studies agreed with the Yoon–Nelson model and indicated that Cu²⁺ break-through time in the column decreased with an increase in flowrate from 3.0 to 10.0 min/mL and decreased in sorption capacity, while it was delayed with increased bed heights from 20 to 30 mm. Complete elution of Ni²⁺ was obtained with 2.0 M H₂SO₄ after selective elution of trace impurities with dilute HCl. Iron in the raffinate was removed via the addition of Ca (OH)₂ at pH 4.0 leaving Zn-Al in the solution. Full article

This study investigated the release of heavy metals from polluted soil under the pore water flow containing nanobubbles (NBs) to simulate natural ebullition. Three types of NBs (CH₄, H₂, and CO₂) were generated in water and characterized, including bubble size, zeta potential, liquid density, and tension. The flow rate used in column tests was optimized to achieve proper soil fluidization and metal desorption or release. The leachate chemistries were monitored to assess the effect of NBs on conductivity, pH, oxidation–reduction potential (ORP), and dissolved oxygen (DO). The results showed that NBs in the pore water flow were significantly more effective in releasing Pb compared to DI water, with CO₂ NB water being the most effective and H₂ NB water being the least effective. CO₂ NB water was also used to rinse column soil contaminated with four different metals (Pb, Cu, Zn, and Cr), which exhibited different leaching kinetics. Moreover, a convective–dispersion–deposition equation (CDDE) model accurately simulated the leaching kinetics and explained the effects of NBs on the key parameters, such as the deposition rate coefficient (K_d), that affect the released metal transport. The findings could provide new insights into soil pollutant release under ebullition and soil remediation using water wash containing NBs. Full article

Antibiotic pollution from manured farmland soils is a major public concern, and their potential interaction with manure particles and/or manure–dissolved organic matter (DOM) often complicates their leaching behaviour. This study investigated the leaching of sulfadiazine (SDZ) and florfenicol (FFC) with manure-DOM in undisturbed field lysimeters and repacked soil columns under natural and simulated rainfall conditions. The results showed that manure-DOM reduced SDZ mass flux, but soil hydrological processes and heavy rainfall events led to accelerated leaching. FFC was more prone to leaching in a manured plot (0.48 µg m⁻² h⁻¹) compared to the control (0.12 µg m⁻² h⁻¹), suggesting DOM facilitated transport of FFC in the field lysimeter study via cotransport mechanisms favored by abundant macropores in the study site. In contrast, SDZ and FFC mobility were reduced in repacked soil columns under manure-DOM conditions, suggesting complexation and adsorption in matrix pores. Two kinetic site models and two-site nonequilibrium adsorption models revealed the existence of nonequilibrium conditions and kinetic sorption processes in the repacked column. FFC exhibited lower leaching potential compared to SDZ in both the repacked column and natural field conditions. Redundancy analyses revealed that FFC had a close relationship with humic-like components (C1 and C3), but SDZ was more related to the protein-like components (C2) of DOM. The presence of manure-DOM may decrease the ecological risks of highly mobile antibiotics under matrix flow through complexations and adsorption. However, a similar scenario in macroporous flow under heavy rainfalls may lead to accelerated leaching. Full article

Leaching and nitrous oxide (N₂O) emissions can represent substantial nitrogen (N) losses from chemical fertilizers, and slow-release fertilizers (SRFs) can mitigate these effects. Thus, biochar can be an alternative from an agronomic and environmental point of view to synthesize SRFs due to its physicochemical characteristics. We investigated the effect of nitrogenous organomineral fertilizers (OMF-N) formulated based on activated biochar on N losses by leaching and N₂O emissions. The OMF-N were developed from a dry mechanical pelleting process with different biochar and urea proportions (2:1; 1:2, and 1:4). Three experiments were conducted using four fertilizer sources (urea, OMF-N 2:1, OMF-N 1:2, and OMF-N 1:4): i. to analyze the kinetics of N release from OMF-N at times: 5, 15, 30, 60, 90, and 120 min; ii. for N₂O emission analysis determined at 3, 6, 10, 14, 24, 44, 54, 64, 74, 84, 104, and 118 days after application to the soil; and iii. for a double factorial design that was adopted to analyze N leaching, consisting of the combination of applying 160 kg N ha⁻¹ of fertilizers in PVC columns at different depths (20, 40, 60, and 80 cm) and analyzed at five times (1, 7, 14, 21, and 28 days). FTIR spectroscopic analysis, specific surface area, porosity, and surface morphology showed physicochemical interactions of N of the OMF with biochar; the N from the OMF interacts physically and chemically binds to the functional surfaces of biochar, delaying the dissolution flow. The OMF-N proved capable of retaining 48% to 60% more NH₄⁺ and reduced the release of N_total from urea from 27% to 60%, as well as reduced N₂O emissions from 47% to 66%. Although absolute CO₂ emissions intensified with the application of OMF-N, its use provides C sequestration in the soil to due to the recalcitrant C of the biochar, which results in a positive input-output balance in the system. The NO₃⁻ concentration profiles revealed that the OMF-N application was able to reduce leaching in the soil to a depth of 80 cm. These studies enabled better understanding of the processes involved in the biochar:urea interaction and revealed that biochar can be used as an organic matrix in the synthesis of SRF. Full article