Rational design of waste anode graphite-derived carbon catalyst to activate peroxymonosulfate for atrazine degradation.

As the rapidly growing number of waste lithium-ion batteries (LIBs), the recycling and reutilization of anode graphite is of increasing interest. Converting waste anode graphite into functional materials may be a sensible option. Herein, a series of carbonaceous catalysts (TG) were successfully prepared using spent anode graphite calcined at various temperatures and applied for activating peroxymonosulfate (PMS) to degrade atrazine (ATZ). The catalyst obtained at 800 °C (TG-800) showed the optimum performance for ATZ removal (99.2% in 6 min). Various experimental conditions were explored to achieve the optimum efficiency of the system. In the TG-800/PMS system, free radicals (e.g., SO4·-, HO·), singlet oxygen (1O2), together with a direct electron transfer pathway all participated in ATZ degradation, and the ketonic (CO) group was proved as the leading catalytic site for PMS activation. The potential degradation routes of ATZ have also been presented. According to the toxicity assessment experiments, the toxicity of the intermediate products decreased. The reusability and universal applicability of the TG-800 were also confirmed. This research not only provides an efficient PMS activator for pollutant degradation, but also offers a meaningful reference for the recovery of waste anode graphite to develop environmentally functional materials.

Cuprous-mediated peroxymonosulfate activation for Fenton-like removal of micropollutants: The function of co-catalyst and the accelerated degradation mechanism.

Introducing co-catalysts to enhance the activation of cuprous-mediated peroxymonosulfate (PMS) and induce the continuous generation of highly reactive oxygen species is promising. The function, effectiveness, and acceleration mechanism of co-catalysts in the cuprous-mediated PMS activation process were fully explored in this work, which focused on rhodamine B as the target contaminants. The results demonstrated that molybdenum (Mo) powder was a superb co-catalyst, and that the reaction of cuprous-mediated PMS system was carried out by surface Mo species as opposed to Mo ions in the solution. The Cu (II)/Cu(I) cycle was primarily encouraged by the Mo0, which also caused abundant ·HO and 1O2 and minimal SO4·- and ·O2- to be produced from PMS. The Mo/Cu2+/PMS system exhibited high removal efficiency towards typical pollutants, especially ciprofloxacin, methyl orange, malachite green, and crystal violet, with removal rates up to 93%, 99%, 97%, and 92%, respectively. Additionally, this system showed excellent adaptability to complex water environments. After four cycles, the Mo powder retained its properties and morphology, and the target pollutants could still maintain an 82% degradation efficiency. This study provides a basis for enhancing cuprous-mediated PMS activation for wastewater treatment.

Prediction of arsenic adsorption onto metal organic frameworks and adsorption mechanisms interpretation by machine learning.

Metal-organic frameworks (MOFs) are promising adsorbents for the removal of arsenic (As) from wastewater. The As removal efficiency is influenced by several factors, such as the textural properties of MOFs, adsorption conditions, and As species. Examining all of the relevant factors through traditional experiments is challenging. To predict the As adsorption capacities of MOFs toward organic, inorganic, and total As and reveal the adsorption mechanisms, four machine learning-based models were developed, with the adsorption conditions, MOF properties, and characteristics of different As species as inputs. The results demonstrated that the extreme gradient boosting (XGBoost) model exhibited the best predictive performance (test R2 = 0.93-0.96). The validation experiments demonstrated the high accuracy of the inorganic As-based XGBoost model. The feature importance analysis showed that the concentration of As, the surface area of MOFs, and the pH of the solution were the three key factors governing inorganic-As adsorption, while those governing organic-As adsorption were the concentration of As, the pHpzc value of MOFs, and the oxidation state of the metal clusters. The formation of coordination complexes between As and MOFs is possibly the major adsorption mechanism for both inorganic and organic As. However, electrostatic interaction may have a greater effect on organic-As adsorption than on inorganic-As adsorption. Overall, this study provides a new strategy for evaluating As adsorption on MOFs and discovering the underlying decisive factors and adsorption mechanisms, thereby facilitating the investigation of As wastewater treatment.

Linkage Microenvironment of Azoles-Related Covalent Organic Frameworks Precisely Regulates Photocatalytic Generation of Hydrogen Peroxide.

Artificial H2 O2 photosynthesis by covalent organic frameworks (COFs) photocatalysts is promising for wastewater treatment. The effect of linkage chemistry of COFs as functional basis to photoelectrochemical properties and photocatalysis remains a significant challenge. In this study, three kinds of azoles-linked COFs including thiazole-linked TZ-COF, oxazole-linked OZ-COF and imidazole-linked IZ-COF were successfully synthesized. More accessible channels of charge transfer were constructed in TZ-COF via the donor-π-acceptor structure between thiazole linkage and pyrene linker, leading to efficient suppression of photoexcited charge recombination. Density functional theory calculations support the experimental studies, demonstrating that the thiazole linkage is more favorable for the formation of *O2 intermediate in H2 O2 production than that of the oxazole and imidazole linkages. The real active sites in COFs located at the benzene ring fragment between pyrene unit and azole linkage.

Mechanistic insights into heavy metals affinity in magnetic MnO2@Fe3O4/poly(m-phenylenediamine) core-shell adsorbent.

Adsorption represents an attractive mean to remediate polluted water. Unfortunately, the surface positive charges, low surface area and complicated separation procedures inhibit the usability of poly (m-phenylenediamine) (PmPD) as an adsorbent for heavy metal removing. To overcome these drawbacks, a magnetic MnO2@Fe3O4/PmPD core-shell adsorbent was designed to remove heavy metals from water. The MnO2 shell, came from the redox reaction between KMnO4 and PmPD, increased the surface area and changed the surface electronegativity. MnO2@Fe3O4/PmPD could be easily separated from water. It showed a significant increase in heavy metals removal efficiency, with maximum capacities of 438.6 mg/g for Pb(II) and 121.5 mg/g for Cd(II), respectively. The affinity between heavy metals and MnO2@Fe3O4/PmPD were mainly due to electrostatic attraction, ion exchanges and coordinated interaction. Density functional theory (DFT) calculations further confirmed that Pb and Cd were bonded with O atoms. The calculated adsorption energy indicated that the (111) MnO2 facet presented stronger adsorption affinity toward Pb(II) than Cd(II). Additionally, FM150 (150 mg) could regenerate 22 L Pb(II) wastewater upon single passage through the filterable column with a flux of 20 mL/min. Thus, the present work demonstrates the promising potential of using MnO2@Fe3O4/PmPD for efficiently removing heavy metals from wastewater.

An ecological scenario prediction model for newly created wetlands caused by coal mine subsidence in the Yanzhou, China.

The ecological model we developed can simulate the state of wetlands and predict ecosystem development by varying both parameter settings and forcing functions. The newly created wetland resulting from large-scale coal mining is a distinct type of wetland, but existing ecological models for this wetland type are limited in number and scope. The Yanzhou coalfield, located in Shandong Province in China, contains a typical newly created wetland that came into being after coal mining subsidence. We developed an ecological model for this wetland that estimates values for four state variables: phytoplankton biomass (A), zooplankton biomass (Z), sediment biomass (D), and hydrophyte biomass (H). Analysis of the results showed that the model was sensitive to changes in nutrient loading. As nutrient loads increased, plankton biomass increased, and the ratio of zooplankton biomass to phytoplankton biomass (Z/A) decreased. We defined three prediction scenarios for the wetland and calculated their eco-exergies to compare the ecological effects for each scenario. The most effective measures to improve the state of the ecosystem are to reduce the subsidence depth and to decrease nutrient loading.

State-of-the-Art Advances and Challenges of Iron-Based Metal Organic Frameworks from Attractive Features, Synthesis to Multifunctional Applications.

Metal organic frameworks (MOFs), as an original kind of organic-inorganic porous material, are constructed with metal centers and organic linkers via a coordination complexation reaction. Among uncountable MOF materials, iron-containing metal organic frameworks (Fe-MOFs) have excellent potential in practical applications owing to their many fascinating properties, such as diverse structure types, low toxicity, preferable stability, and tailored functionality. Here, recent research progresses of Fe-MOFs in attractive features, synthesis, and multifunctional applications are described. Fe-MOFs with porosity and tailored functionality are discussed according to the design of building blocks. Four types of synthetic methods including solvothermal, hydrothermal, microwave, and dry gel conversion synthesis are illustrated. Finally, the applications of Fe-MOFs in Li-ion batteries, sensors, gas storage, separation in gas and liquid phases, and catalysis are elucidated, focusing on the mechanism. The aim is to provide prospects for extending Fe-MOFs in more practical applications.

Modulation of Bi2 MoO6 -Based Materials for Photocatalytic Water Splitting and Environmental Application: a Critical Review.

Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, Bi2 MoO6 has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi2 MoO6 suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect-introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi2 MoO6 . To accelerate further developments of Bi2 MoO6 in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi2 MoO6 -based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi2 MoO6 -based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi2 MoO6 are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi2 MoO6 -based photocatalysts for environmental pollution control and green energy development.

Emergy and eco-exergy evaluation of wetland restoration based on the construction of a wetland landscape in the northwest Yunnan Plateau, China.

The synthesis of emergy and eco-exergy is one of the most effective methods in the evaluation of wetland restoration. In this study, the landscape design for the restoration of Napahai wetland in the northwest Yunnan Plateau of China was carried out, and the sustainability and self-organizational level of the wetland before and after restoration were evaluated using eco-exergy and emergy combined with the Lorenz curve method. The results showed that wetland plants rapidly increased from 26 species to 52 species after two years, with a gradual decrease in pollutant-enduring species and the reappearance of the marsh plants Sparganium simplex and Batrachium bungei communities that had disappeared for many years, which speed up the succession and structure organization of the community. The wetland was better for biomass accumulation and soil improvement after restoration, and there were significant decreases in the concentrations of TP, TN and COD in the water body. The sustainability index values for the wetland ranged from 4.17 before restoration to 2385.16 after restoration, and the ecosystem service values for the wetland after restoration was 1.95 times higher than that before restoration. These results confirmed that the wetland after restoration was less environmentally stressed and more sustainable. In addition, the values of eco-exergy and specific eco-exergy after restoration were 1.70 and 1.01 times higher than that before restoration, respectively; the emergy/exergy ratio was lower for the wetland after restoration. These results suggested that the wetland after restoration had higher complexity and self-organizational level, and became a self-sustaining and resilient natural system. This study represents a new exploration of the emergy and eco-exergy evaluation on the wetland restoration, providing an engineering demonstration and a reference for the landscape design of wetland restoration in the plateau region.

Molecular docking simulation on the interactions of laccase from Trametes versicolor with nonylphenol and octylphenol isomers.

The biodegradation of nonylphenol (NP) and octylphenol (OP) isomers by laccase has attracted increasing concerns. However, the interaction mechanism between these isomers and laccase remains unclear, especially for fungal laccase. In this work, molecular docking was employed to study this issue. The results indicated that the structural characteristic of alkyl chain (position and branching degree) affected the interactions between Trametes versicolor (T. versicolor) laccase and isomers. The binding affinity between them was closely related to the position and branching degree of alkyl chain in isomers. The binding affinities between linear isomers and T. versicolor laccase were para-position < meta-position < ortho-position. For selected branched 4-NP, the isomers with bulky α-substituent in alkyl chain had higher binding affinities. In addition, hydrophobic contacts between T. versicolor laccase and NP or OP isomers were necessary, while H-bonds were optional. The isomers with similar structure may have more common residues involved in hydrophobic contacts. The H-bonds of selected NPs and OPs were all connected with phenolic hydroxyl. These findings provide an insight into detailed interaction mechanism between T. versicolor laccase and isomers of NP and OP. It is helpful to broaden the knowledge of degradation technology of NPs and OPs and provide theoretical basis on biological remediation of these contaminants.

Effective treatment of oily scum via catalytic wet persulfate oxidation process activated by Fe2.

Oily scum, a hazardous by-product of petroleum industry, need to be deposed urgently to reduce environmental risks. This paper introduces catalytic wet persulfate oxidation (CWPO) process in the treatment of oily scum to realize risk relief. Under the activation of heat and Fe2+, persulfate (PS) was decomposed into sulfate radicals and hydroxyl radicals, which played a major role on the degradation of petroleum hydrocarbons. The effects of wet air oxidation (WAO) and CWPO process on the degradation of oily scum were compared. In CWPO process, the total petroleum hydrocarbons (TPHs) content of oily scum was decreased from 92.63% to 16.75%, which was still up to 70.19% in WAO process. The degradation rate of TPHs in CWPO process was about 3.38 times higher than that in WAO process. The great performance of CWPO process was also confirmed by elemental analysis, which indicated that the C and H contents of oily scum were reduced significantly by CWPO process. These results indicated that CWPO process has high potential on the degradation of oily scum for environmental protection.

Implication of graphene oxide in Cd-contaminated soil: A case study of bacterial communities.

The application of graphene oxide (GO) has attracted increasing concerns in the past decade regarding its environmental impacts, except for the impact of GO on a metal-contaminated soil system, due to its special properties. In the present work, the effects of GO on the migration and transformation of heavy metals and soil bacterial communities in Cd-contaminant soil were systematically evaluated. Soil samples were exposed to different doses of GO (0, 1, and 2 g kg-1) over 60 days. The Community Bureau of Reference (BCR) sequential extraction procedure was used to reflect the interaction between GO and Cd. Several microbial parameters, including enzyme activities and bacterial community structure, were measured to determine the impacts of GO on polluted soil microbial communities. It was shown that Cd was immobilized by GO throughout the entire exposure period. Interestingly, the structure of the bacterial community changed. The relative abundance of the major bacterial phyla (e.g., Acidobacteria and Actinobacteria) increased, which was possibly attributed to the reduced toxicity of Cd in the presence of GO. However, GO exerted an adverse influence on the relative abundance of some phyla (e.g., WD272 and TM6). The diversity of bacterial communities was slightly restricted. The functional bacteria related to carbon and the nitrogen cycling were also affected, which, consequently, may influence the nutrient cycling in soil.

Assessment of micro-polarity anisotropy as a function of surfactant packing in sodium dodecyl sulphonate-hexane reverse micelles.

The micro-polarity anisotropy behaviour across the aqueous phase of a SDS (sodium dodecyl sulphonate)-hexane reverse micelle (RM) relies on the SDS packing in the oil-water interfacial self-assembled surfactant structure of the RM.

Effect-Directed Analysis of Aryl Hydrocarbon Receptor Agonists in Sediments from the Three Gorges Reservoir, China.

The construction of the Three Gorges Dam (TGD) in the Yangtze River raises great concern in ecotoxicological research since large amounts of pollutants enter the Three Gorges Reservoir (TGR) water bodies after TGD impoundment. In this work, effect-directed analysis (EDA), combining effect assessment, fractionation procedure, and target and nontarget analyses, was used to characterize aryl hydrocarbon receptor (AhR) agonists in sediments of the TGR. Priority polycyclic aromatic hydrocarbons (PAHs) containing four to five aromatic rings were found to contribute significantly to the overall observed effects in the area of Chongqing. The relatively high potency fractions in the Kaixian area were characterized by PAHs and methylated derivatives thereof and heterocyclic polycyclic aromatic compounds (PACs) such as dinaphthofurans. Benzothiazole and derivatives were identified as possible AhR agonists in the Kaixian area based on nontarget liquid chromatography-high resolution mass spectrometry (LC-HRMS). To our knowledge, this study is the first one applying the EDA approach and identifying potential AhR agonists in TGR.

The effect of temperature on repeat swimming performance in juvenile qingbo (Spinibarbus sinensis).

To investigate the effect of temperature on the repeat constant acceleration swimming performance and on the metabolic recovery capacity in juvenile qingbo (Spinibarbus sinensis), their constant acceleration test speed (U(CAT)) and excess post-exercise oxygen consumption (EPOC) recovery process were measured twice with 1-h intervals at different acclimation temperatures (10, 15, 20, 25 and 30 °C). Temperature significantly affected U(CAT), the pre-exercise metabolic rate (MO(2)), metabolic peak values (MO(2peak)), the metabolic scope (MS, MO(2peak)--pre-exercise MO(2)) and the magnitude of the EPOC (P < 0.05). These parameters significantly increased as the temperature increased from 15 to 25 °C and significantly decreased (U(CAT) and EPOC magnitude) or did not change (MO(2peak) and MS) when the temperature increased from 25 to 30 °C in the first test (P < 0.05). The relationships between temperature (T) and these parameters (U(CAT), MO(2peak), MS and EPOC magnitude) in the first test were as follows: U(CAT) = 62.14/{1 + [(T - 25.1)/21.1](2)} (r = 0.847, P < 0.001, n = 40); MO(2peak) = 1,052.11/{1 + [(T - 29.2)/18.9](2)} (r = 0.901, P < 0.001, n = 39); MS = 753.74/{1 + [(T - 27.1)/18.6](2)} (r = 0.768, P < 0.001, n = 39); and EPOC = 195.42/{1 + [(T - 25.6)/8.7](2)} (r = 0.752, P < 0.001, n = 39). The optimal temperatures for U(CAT), MO(2peak), MS and EPOC magnitude in juvenile qingbo were 25.1, 29.2, 27.1 and 28.6 °C, respectively. Repeat exercise had different effect on U(CAT) and EPOC magnitude at different temperature (interaction effect, P < 0.05). There was no difference in U(CAT) and in EPOC magnitude between the first and second tests at low temperatures (10-20 °C). However, both U(CAT) and EPOC magnitude decreased significantly during the second test compared with the first test at high temperatures (25 and 30 °C) (P < 0.05). The present study showed that the recovery of the constant acceleration swimming performance was poorer at higher temperatures than at low temperatures in juvenile qingbo. These differences may be related to larger anaerobic metabolism, a lower pH value in the blood, larger ionic fluids and/or higher levels of hormones present at high temperatures.

Spatial and temporal variation of heavy metal risk and source in sediments of Dongting Lake wetland, mid-south China.

Surface sediments of Dongting Lake wetland were collected from ten sites to investigate variation trend, risk and sources of heavy metal distribution in dry seasons of 2011∼2013. The three-year mean concentrations (mg/kg) of Cr, Cu, Pb, Cd, Hg and As were 91.33, 36.27, 54.82, 4.39, 0.19 and 25.67, respectively, which were all higher than the corresponding background values. Sediment quality guidelines (SQGs) and Geo-accumulation index (Igeo) were used for the assessment of pollution level of heavy metals. The pollution risk of Cd, Hg and As were great and that of Cr needed urgent attention because of its obvious increase. Pollution load index (PLI) and geographic information system (GIS) methods were conducted to assess spatial and temporal variation of heavy metal contamination. Results confirmed an increased contamination contribution inflow from Xiang River. Multivariate statistical analyses were applied to identify contribution sources of heavy metal, which showed anthropogenic origin mainly from mining, smelting, chemical industry and agricultural activity.

Yangtze Three Gorges Reservoir, China: A holistic assessment of organic pollution, mutagenic effects of sediments and genotoxic impacts on fish.

Besides obvious benefits, the Three Gorges Dam's construction resulted in new pollution scenarios with the potentials to threaten the Three Gorges Reservoir (TGR) ecosystem. In order to record organic contamination, to find links to ecotoxicological impacts and to serve as reference for ensuing monitoring, several sites in the TGR area were screened applying the triad approach with additional lines-of-evidence as a holistic assessment method. Sediments and the benthic fish species Pelteobagrus vachellii were sampled in 2011 and 2012 to determine organic pollution levels, mutagenic potentials and genotoxic impacts. Two regional hot-spots near the cities of Chongqing and Kaixian were identified and further investigated in 2013. Only polycyclic aromatic hydrocarbons (PAHs) could be detected in sediments in 2011 (165-1653ng/g), emphasizing their roles as key pollutants of the area. Their ubiquity was confirmed at Chongqing (150-433ng/g) and Kaixian (127-590ng/g) in 2013. Concentrations were comparable to other major Chinese and German rivers. However, the immense sediment influx suggested a deposition of 216-636kgPAH/day (0.2-0.6mgPAH/(m(2)·day)), indicating an ecotoxicological risk. PAH source analysis highlighted primary impacts of combustion sources on the more industrialized upper TGR section, whereas petrogenic sources dominated the mid-low section. Furthermore, sediment extracts from several sites exhibited significant activities of frameshift promutagens in the Ames fluctuation assay. Additionally, significant genotoxic impairments in erythrocytes of P. vachellii were detected (Chongqing/Kaixian), demonstrating the relevance of genotoxicity as an important mode of action in the TGR's fish. PAHs, their derivatives and non-target compounds are considered as main causative agents.

Role of low-concentration monorhamnolipid in cell surface hydrophobicity of Pseudomonas aeruginosa: adsorption or lipopolysaccharide content variation.

A role of rhamnolipid biosurfactant to enhance the biodegradation of hydrocarbons is known to be enhancing bacterial cell surface hydrophobicity (CSH) and adhesion of cells to hydrocarbons. Assumptions regarding the mechanism for rhamnolipid in changing CSH of Gram-negative bacteria are rhamnolipid-induced release of lipopolysaccharide (LPS) from the cell's outer membrane and adsorption/orientation of rhamnolipid on the cell surface. In this study, the relation between cell-wall LPS or rhamnolipid content and CSH of a Pseudomonas aeruginosa bacterium subjected to rhamnolipid treatment was investigated to add insights to the mechanism. Results showed that the initial CSH was determined by the type of substrate the cells grow on and the stage of growth. For glucose-grown cells with low initial CSH and high LPS content, rhamnolipid sorption in cell wall had no discernable effect on CSH. For cells grown on glycerol with medium initial CSH and low LPS content, rhamnolipid sorption increased CSH of exponential-phase cells but decreased that of stationary-phase cells. For hexadecane-grown cells with high initial CSH and high LPS content, rhamnolipid sorption decreased CSH of both exponential-phase and stationary-phase cells. The results indicated that CSH has a better correlation to the content of rhamnolipid in the cell wall than to the content of LPS in the presence of rhamnolipid treatment and that rhamnolipid adsorption may be an important mechanism for rhamnolipid to alter CSH of P. aeruginosa.

The effects of fasting on swimming performance in juvenile qingbo (Spinibarbus sinensis) at two temperatures.

We measured the following variables to investigate the effects of fasting and temperature on swimming performance in juvenile qingbo (Spinibarbus sinensis): the critical swimming speed (Ucrit), resting metabolic rate (MO2rest) and active metabolic rate (MO2active) of fish fasting for 0 (control), 1, 2 and 4 weeks at low and high acclimation temperatures (15 and 25°C). Both fasting treatment and temperature acclimation had significant effects on all parameters measured (P<0.05). Fasting at the higher temperature had a negative effect on all measured parameters after 1 week (P<0.05). However, when acclimated to the lower temperature, fasting had a negative effect on Ucrit until week 2 and on (MO2rest), (MO2active) and metabolic scope (MS, (MO2active)-(MO2rest)) until week 4 (P<0.05). The values of all parameters at the lower temperature were significantly lower than those at the higher temperature in the identical fasting period groups except for (MO2rest) of the fish that fasted for 2 weeks. The relationship between fasting time (T) and Ucrit was described as Ucrit(15)=-0.302T(2)-0.800T+35.877 (r=0.781, n=32, P<0.001) and Ucrit(25)=0.471T(2)-3.781T+50.097 (r=0.766, n=32, P<0.001) at 15 and 25°C, respectively. The swimming performance showed less decrease in the early stage of fasting but more decrease in the later stage at the low temperature compared to the high temperature, which might be related to thermal acclimation time, resting metabolism, respiratory capacity, energy stores, enzyme activity in muscle tissue and energy substrate utilization changes with fasting between low and high temperatures. The divergent response of the swimming performance to fasting in qingbo at different temperatures might be an adaptive strategy to seasonal temperature and food resource variation in their habitat.

Feature engineering for improved machine-learning-aided studying heavy metal adsorption on biochar.

Due to the broad interest in using biochar from biomass pyrolysis for the adsorption of heavy metals (HMs) in wastewater, machine learning (ML) has recently been adopted by many researchers to predict the adsorption capacity (η) of HMs on biochar. However, previous studies focused mainly on developing different ML algorithms to increase predictive performance, and no study shed light on engineering features to enhance predictive performance and improve model interpretability and generalizability. Here, based on a dataset widely used in previous ML studies, features of biochar were engineered-elemental compositions of biochar were calculated on mole basis-to improve predictive performance, achieving test R2 of 0.997 for the gradient boosting regression (GBR) model. The elemental ratio feature (H-O-2N)/C, representing the H site links to C (non-active site to HMs), was proposed for the first time to help interpret the GBR model. The (H-O-2N)/C and pH of biochar played essential roles in replacing cation exchange capacity (CEC) for predicting η. Moreover, expanding the coverages of variables by adding cases from references improved the generalizability of the model, and further validation using cases without CEC and specific surface area (R2 0.78) and adsorption experimental results (R2 0.72) proved the ML model desirable. Future studies in this area may take into account algorithm innovation, better description of variables, and higher coverage of variables to further increase the model's generalizability.