Efficient degradation of antibiotic wastewater by biochar derived from water hyacinth stems via periodate activation: pyridinic N and carbon structures improved the electron transfer process.

Biochar-activated periodate (PI) is a promising technology toward antibiotic wastewater purification. However, the mechanism of pyrolysis temperature on PI activation efficiency by biochar has not yet been revealed. Herein, this work selected water hyacinth stems as raw materials to prepare biochar with different pyrolysis temperatures (400, 500, 600, and 700 °C), and applied it to degrade tetracycline (TC) wastewater through PI activation. The results show that biochar with a pyrolysis temperature of 700 °C (BC-700) possesses the best TC degradation performance (∼100% within 30 min). Besides, the degradation of TC by BC-700 is less interfered by coexisting anions and water matrix, and exhibits good reusability. Quenching experiments and open circuit voltage tests verified that IO3•, 1O2, and reactive complex BC-PI* are active species involved in TC degradation. In addition, by constructing the relationship between biochar surface properties and degradation rate kobs, it was revealed that the dominant role of pyridinic N in PI adsorption and formation of reactive complexes as well as the promotion of sp2-hybridized carbon in the electron transfer process. This work provides novel insights into the application of biochar in antibiotic wastewater treatment via PI activation.

Decision-Making Teaching Practice Based on the Maximum Entropy Method in a Water Engineering Economics Course.

The purpose of this paper is to put forward a decision model with wide applicability and differentiated decision scheme scores so as to improve the ability of students to learn during a water engineering economics course. The main novelty and contributions of this paper are that the multi-attribute decision-making method proposed is more objective and does not require rich subjective experience from decision-makers in the application process, which is particularly suitable for beginners who are learning in a water engineering economics course. The method involves standardizing each index value of the decision scheme first, constructing the objective function of maximum entropy distribution, calculating the weight of each index by the genetic algorithm, and finally ranking the pros and cons of the scheme according to the score of each scheme. The example results of three water engineering scheme decisions show that the maximum entropy model proposed in this paper can achieve reasonable decision results, and there is a large degree of differentiation between the decision schemes. The proposed scheme, a decision maximum entropy model, has wide applicability, can improve the rationality of the decisions made regarding water engineering schemes, and can be popularized and applied when teaching decision-making in water engineering economics courses.

Novel scheme for synergistic purification of copper mine tailings and orthophosphate.

Copper tailings (CTs) and orthophosphate are major environmental pollutants. CTs cause severe heavy metal pollution, and orthophosphate is one of the primary causes of water body eutrophication. This study aimed to alleviate heavy metal pollution by CTs and the eutrophication of water caused by orthophosphate. To this end, a 50 mg/L orthophosphate was used as a chemically active leaching solution and passed through a CT soil column. The tail water was then collected. Laboratory leaching tests showed that the thermally modified CTs effectively trapped orthophosphate, and the orthophosphate content in the leachate was 0.15 mg/L. After chemical washing, Cu2+, Cd2+, and Zn2+ were tested in the tail water, and the heavy metal ions in the tail water were removed using an advanced treatment technology. After treatment with 20.0 g/L water hyacinth biochar (WHBC), the removal rates (R%) of Cu2+, Cd2+, and Zn2+ were 99.48, 94.94, and 94.84%, respectively. These results demonstrated that this novel scheme for the synergistic purification of CTs and orthophosphate was feasible in the laboratory. This study provides new theoretical guidance and technical support for CT soil heavy metal remediation and water eutrophication treatment.

Hydroxylamine-enhanced Fe(II)-peroxymonosulfate activation for efficient degradation of organic pollutants: optimization by response surface methodology.

In this work, the response surface methodology (RSM) was used to model and optimize the hydroxylamine (HA) enhanced Fe(II)/peroxymonosulfate (PMS) process. The enhanced effect of HA on the degradation efficiency of Orange II (AO7) in the Fe(II)/PMS system was quantitatively analyzed. Pareto analysis showed that the individual and interactive effects of HA, Fe(II) and PMS were of the following order: HA > Fe(II) > PMS and Fe(II)/PMS > HA/PMS > Fe(II)/HA. The optimal conditions of HA/Fe(II)/PMS system were as follows: Fe(II) concentration was 34.0 µM, HA concentration was 0.4 mM, and PMS concentration was 0.9 mM. When the initial pH was 4.0-6.0, the degradation efficiency of AO7 in the HA/Fe(II)/PMS system was significantly higher than that in the Fe(II)/PMS system (P < 0.05). Hydroxylamine enhances the degradation of AO7 in the Fe(II)/PMS system by reducing Fe(III) to Fe(II). The results of quenching experiment showed that SO4•- was the dominating reactive oxygen species (ROS) in the HA/Fe(II)/PMS system. In the HA/Fe(II)/PMS system, CO32- and humic acid inhibited the degradation efficiency of AO7. This work provides a novel mathematical model for the degradation of AO7 in the HA/Fe(II)/PMS system, which can be popularized and applied in similar experiments.

Optimize the preparation of Fe3O4-modified magnetic mesoporous biochar and its removal of methyl orange in wastewater.

In this paper, Eichhornia Crassipes stems were used as biomass feedstock, and Fe2+ was used as the precursor solution to prepare Fe3O4-modified magnetic mesoporous biochar (Fe3O4@BC). By using Box-Behnken design (BBD) response surface methodology, the influences of three preparation parameters (X1 = Fe2+ concentration, X2 = pyrolysis temperature and X3 = pyrolysis time) on the adsorption of methyl orange (MO) by Fe3O4@BC were investigated, and a reliable response surface model was constructed. The results show that X1X2 and X1X3 have a significant influence on the adsorption of MO by Fe3O4@BC. The surface area and pore volume of Fe3O4@BC are controlled by all preparation parameters. The increase of pyrolysis time will significantly reduce the -OH on the surface of Fe3O4@BC and weaken its MO adsorption capacity. Through the numerical optimization of the constructed model, the optimal preparation parameters of Fe3O4@BC can be obtained as follows: Fe2+ concentration = 0.27 mol/L, pyrolysis temperature = 405 °C, and pyrolysis time = 3.2 h. The adsorption experiment shows that the adsorption of Fe3O4@BC to MO is a spontaneous exothermic process, and the adsorption capacity is maximum when pH = 4. The adsorption kinetics and adsorption isotherms of Fe3O4@BC to MO conform to the pseudo-second-order kinetics and Sips model, respectively. Mechanism analysis shows that electrostatic interaction and H bond formation are the main forces for Fe3O4@BC to adsorb MO. This research not only realizes a new way of resource utilization of Eichhornia Crassipes biomass but also enriches the preparation research of magnetic biochar.

Adsorption characteristics and mechanism of norfloxacin in water by γ-Fe2O3@BC.

Using waste pomelo peel as raw material, pomelo peel-based biochar (BC) was prepared by pyrolysis at 400 °C, and the pomelo peel-based biochar was prepared by loading γ-Fe2O3 onto the surface of the pomelo peel-based biochar by unlimited oxygen chemical precipitation. The results showed that the pomelo peel biochar loaded with γ-Fe2O3 had higher specific surface area and larger pore volume. The load of γ-Fe2O3 gives γ-Fe2O3@BC excellent magnetic separation ability, and its magnetic saturation intensity is as high as 30.60 emu/g. BC and γ-Fe2O3@BC were applied to remove norfloxacin (NOR) from a water body. It was found that the adsorption of NOR by both of them followed the pseudo-second-order kinetic model. The adsorption isotherm mainly conforms to the Sips model, and the adsorption process of NOR is a spontaneous endothermic reaction. The pH and ionic strength have a great influence on the adsorption of NOR by BC and γ-Fe2O3@BC, and they play a role mainly by influencing the morphology of NOR in water. The adsorption mechanism showed that cation exchange and hydrogen bonding were the main forces for BC to adsorb NOR. Moreover, the γ-Fe2O3 particles enhanced the hydrophobicity of the pomelo peel-based biochar, making the hydrophobicity become the main force for the adsorption of NOR by the γ-Fe2O3@BC. The adsorption-desorption experiment showed that after four cycles of recycling, the adsorption capacity of γ-Fe2O3@BC for NOR was still up to 61.43% of the initial adsorption capacity, and it had a good recycling property.

Application of copper tailings combined with persulfate for better removing methyl orange from wastewater.

In this paper, wasted copper tailings (CT) were used to activate persulfate (PS) to degrade azo dye methyl orange (MO). The results show that a large amount of FeS2 contained in CT can slowly release Fe2+ in the aqueous solution to activate PS to generate reactive oxygen species to degrade MO. When the dosage of CT and PS was 2 g/L and 3 mM respectively, the MO degradation efficiency of 20 mg/L in the CT/PS system was 96.52% within 60 min. At the same time, it is found that CT has a certain adsorption capacity for MO, and the intra-particle diffusion model can well describe the adsorption process of MO by CT. The effects of related reaction parameters (CT dosage, PS dosage, initial MO concentration and solution pH) on MO degradation in CT/PS system were investigated. Compared with the direct addition of an equal amount of Fe2+ as in the CT/PS system, for homogeneous activated PS to degrade MO (Fe2+/PS), the results showed that the degradation efficiency of Fe2+/PS system for MO was lower than that of CT/PS system due to excessive Fe2+ consumption of SO4 ·-. By comparing the Fe2+ and Fe3+ concentrations in the two systems, it was found that the CT/PS system could maintain a low Fe2+ concentration during the reaction process, and the Fe2+ released by CT could be used by PS to degrade MO more efficiently. The free radical scavenging experiments showed that the reactive oxygen species in the CT/PS system was mainly SO4 ·-. This study not only proposed a new CT utilization approach, but also solved the problem of reduced degradation efficiency of organic pollutants caused by excessive Fe2+ in the Fenton-like reaction.

Adsorptive removal of phosphate from aqueous solutions by thermally modified copper tailings.

In this study, thermally modified copper tailings (TMCT) were used to adsorb phosphate in aqueous solutions through experiments. The characterization of TMCT and unmodified copper tailings (UMCT) was done by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The effects of pH, adsorbent dosage, contact time, and initial phosphate concentrations on phosphate adsorption were investigated. We studied the adsorption ability of TMCT and UMCT at 298 K, and the Langmuir isotherm model closely described the adsorption isotherm data, indicating that the maximum adsorption capacity (Qmax) of the TMCT and UMCT was 14.25 mg g-1 and 2.08 mg g-1, respectively. In addition, the adsorption isotherms of TMCT were analyzed at 288 K, 298 K, and 308 K, and the calculated Qmax of phosphate were 9.83 mg g-1 at 288 K, 14.25 mg g-1 at 298 K, and 11.55 mg g-1 at 308 K. Finally, the concentration of copper in the effluent was checked, and the content was 130 mg L-1. Then, the effluent was adsorbed by Eichhornia crassipes stem biochar; after adsorption, the concentration of the secondary effluent was 0.7 mg L-1, which is lower than the grade II classification (1.0 mg L-1) of the integrated wastewater discharge standard (GB8978-1996). The results suggest that the TMCT can be effectively and environmentally friendly used to adsorb phosphate from aqueous solutions.

Entropy Value-Based Pursuit Projection Cluster for the Teaching Quality Evaluation with Interval Number.

The issue motivating the paper is the quantification of students' academic performance and learning achievement regarding teaching quality, under interval number condition, in order to establish a novel model for identifying, evaluating, and monitoring the major factors of the overall teaching quality. We propose a projection pursuit cluster evaluation model, with entropy value method on the model weights. The weights of the model can then be obtained under the traditional real number conditions after a simulation process by Monte Carlo for transforming interval number to real number. This approach can not only simplify the evaluation of the interval number indicators but also give the weight of each index objectively. This model is applied to 5 teacher data collected from a China college with 4 primary indicators and 15 secondary sub-indicators. Results from the proposed approach are compared with the ones obtained by two alternative evaluating methods. The analysis carried out has contributed to having a better understanding of the education processes in order to promote performance in teaching.

Effect of heating temperature and time on the phosphate adsorption capacity of thermally modified copper tailings.

In the present study, copper tailings were treated at different temperatures (50-650 °C) and for various times (0.5-6 hours) and their phosphate adsorption capacity was investigated. The results showed that heating temperature significantly affected adsorption capacity. The highest capacity was observed in treatments at 310-350 °C. Heating time did not influence phosphate adsorption ability of copper tailings. Scanning electron microscopy, Barrett-Joyner-Halenda (BJH), and Fourier transform infrared spectroscopy (FTIR) were employed to characterize untreated copper tailings (raw CT) and copper tailings heated at 340 °C (CT340). The results showed that CT340 had a rougher surface, more and smaller pores, a larger surface area and higher FTIR transmittance than raw CT. These changes in texture might explain the increased phosphate adsorption of thermally modified copper tailings. Mathematical modeling showed that the Langmuir nonlinear model was the best fit to the current data. The maximum adsorption capacities of raw CT and CT340 were predicted as 2.08 mg/g and 14.25 mg/g at 298 K, pH 6.0, respectively.

Evaluating Sustainability of Regional Water Resources Based on Improved Generalized Entropy Method.

The sustainability of regional water resources has important supporting data needed for establishing policies on the sustainable development of the social economy. The purpose of this paper is to propose an assessment method to accurately reflect the sustainability of regional water resources in various areas. The method is based on the relative entropy of the information entropy theory. The steps are as follows. Firstly, the pretreatment of the evaluation sample data is required, before the relative entropy of each standard evaluation sample and evaluation grade (SEG) is calculated to obtain the entropy weight of each evaluation index. After this, the entropy weighted comprehensive index (WCI) of the standard evaluation grade sample is obtained. The function relation between WCI and SEG can be fitted by the cubic polynomial to construct the evaluation function. Using the above steps, a generalized entropy method (GEM) for the sustainable assessment of regional water resources is established and it is used to evaluate the sustainability of water resources in the Pingba and Huai River areas in China. The results show that the proposed GEM model can accurately reflect the sustainable water resources in the two regions. Compared with the other evaluation models, such as the Shepherd method, Artificial Neural Network and Fuzzy comprehensive evaluation, the GEM model has larger differences in its evaluation results, which are more reasonable. Thus, the proposed GEM model can provide scientific data support for coordinating the relationship between the sustainable development and utilization of regional water resources in order to improve the development of regional population, society and economy.

Optimization of target biochar for the adsorption of target heavy metal ion.

The purpose of this work is to study the pyrolysis conditions of target biochar suitable for target heavy metal ion, to characterize the optimized target biochar, and to study the adsorption performance of biochar. With Cu2+ and Zn2+ as the target pollutants, the pyrolysis conditions involved in the preparation process as pyrolysis temperature, pyrolysis time, and heating rate were evaluated and optimized from Box-Behnken Design (BBD), response surface methodology (RSM) and desirability function, the optimized pyrolysis conditions of target biochar for Cu2+ (Cu-BC) and Zn2+ (Zn-BC) were obtained. The optimum pyrolysis parameters for Cu-BC and Zn-BC were pyrolysis time of 3.09 and 2.19 h, pyrolysis temperature of 425.27 and 421.97 °C, and heating rate of 19.65 and 15.88 °C/min. The pseudo-second-order kinetic and Langmuir isotherm model proved to be the best fit for the equilibrium data, with a maximum adsorption capacity (Qmax) fitted by Langmuir model were 210.56 mg/g for Cu2+ by Cu-BC and 223.32 mg/g for Zn2+ by Zn-BC, which were both higher than the Qmax of unoptimized biochar (BC) for Cu2+ (177.66 mg/g) and Zn2+ (146.14 mg/g). The physical properties, chemical structure, surface chemistry properties of Cu-BC and Zn-BC were characterized by Zeta potential meter, Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). This study puts forward a new perspective for optimizing target biochar production for special environmental application.

Optimization of biochar preparation from the stem of Eichhornia crassipes using response surface methodology on adsorption of Cd2.

In this study, preparation of Eichhornia crassipes stem biochar (ECSBC) was optimized and applied for the removal of Cd2+ from aqueous solution. To obtain the best adsorption capacity of ECSBC, the response surface methodology (RSM) was used to optimize the preparation conditions of ECSBC (OECSBC). The interactions among heating time (X1), heating temperature (X2) and heating rate (X3) were designed by Box-Behnken Design (BBD) experiments. The software gave seventeen runs experiment within the optimal conditions towards two response variables (removal rate and adsorption capacity for Cd2+). The results showed that the mathematical model could fit the experimental data very well and the significance of the influence factors followed the order as heating temperature (X2) > heating rate (X3) > heating time (X1), and the influence of interaction term is: X1 and X2 (heating time and heating temperature) > X2 and X3 (heating temperature and heating rate) > X1 and X3 (heating time and heating rate). Based on the analysis of variance and the method of numerical expected function, the optimal conditions were heating time of 2.42 h, heating temperature of 393 °C, and heating rate of 15.56 °C/min. Under the optimum conditions, the predicted the maximum removal rate and adsorption capacity were 85.2724% and 21.168 mg/g, respectively, and the experimental value of removal rate and adsorption capacity for Cd2+ were 80.70% and 20.175 mg/g, respectively, the deviation from the predicted value were 5.36% and 4.69%. The results confirmed that the RSM can optimize the preparation conditions of ECSBC, and the adsorption capacity of OECSB was improved.