Machine learning vs. statistical model for prediction modeling and experimental validation: Application in groundwater permeable reactive barrier width design.

Permeable reactive barrier (PRB) is an effective in-situ technology for groundwater remediation. The important factors in PRB design are the width and reactive material. In this study, the beaded coal mine drainage sludge (BCMDS) was employed as the filling material to adsorb arsenic pollutants in groundwater, aiming to design the width of PRB. The design methods involving traditional continue column experiments and empirical formulas, as well as machine learning (ML) predictions and statistical methods, which are compared with each other. Traditional methods are determined based on breakthrough curves under several conditions. ML method has advantages in predicting the width of mass transfer zone (WMTZ), which simultaneously consider the characteristics of material, pollutant, and environmental conditions, with data collected from articles. After data preprocessing and model optimizing, selected the XGBoost algorithm based on the high accuracy, which shows good prediction for WMTZ (R2 = 0.97, RMSE = 0.15). The experimentally derived WMTZ values were also used to validate the predictions, demonstrating the ML low error rate of 7.04 % and the feasibility. Subsequent statistical analysis of multiple linear regression (MLR) showed the error rate of 39.43 %, interpret superiority of ML due to the complexity of influencing factors and the insufficient precision of math regression. Compared to traditional width design methods, ML can improve design efficiency and save experimental time and manpower. Further expansion of the dataset and optimization of algorithms could enhance the accuracy of ML, overcoming existing limitations and gaining broader applications.

Utilizing machine learning for reactive material selection and width design in permeable reactive barrier (PRB).

Permeable reactive barrier (PRB) is an important groundwater treatment technology. However, selecting the optimal reactive material and estimating the width remain critical and challenging problems in PRB design. Machine learning (ML) has advantages in predicting evolution and tracing contaminants in temporal and spatial distribution. In this study, ML was developed to design PRB, and its feasibility was validated through experiments and a case study. ML algorithm showed a good prediction about the Freundlich equilibrium parameter (R2 0.94 for KF, R2 0.96 for n). After SHapley Additive exPlanation (SHAP) analysis, redefining the range of the significant impact factors (initial concentration and pH) can further improve the prediction accuracy (R2 0.99 for KF, R2 0.99 for n). To mitigate model bias and ensure comprehensiveness, evaluation index with expert opinions was used to determine the optimal material from candidate materials. Meanwhile, the ML algorithm was also applied to predict the width of the mass transport zone in the adsorption column. This procedure showed excellent accuracy with R2 and root-mean-square-error (RMSE) of 0.98 and 1.2, respectively. Compared with the traditional width design methodology, ML can enhance design efficiency and save experiment time. The novel approach is based on traditional design principles, and the limitations and challenges are highlighted. After further expanding the data set and optimizing the algorithm, the accuracy of ML can make up for the existing limitations and obtain wider applications.

Comparison of effects of multiple oxidants with an ultrasonic system under unified system conditions for bisphenol A degradation.

Bisphenol A (BPA) as a trace contaminant has been reported, due to widespread use in the plastics industry. This study applied the 35 kHz ultrasound (US) to activate four different common oxidants (H2O2, HSO5-, S2O82-, and IO4-) for BPA degradation. With increasing initial concentration of oxidants, the degradation rate of BPA increased. The synergy index confirmed that a synergistic relationship between US and oxidants. This study also examined the impact of pH and temperature. The results showed that the kinetic constants of US, US-H2O2, US-HSO5- and US-IO4-decreased when the pH increased from 6 to 11. The optimal pH for US-S2O82- was 8. Notably, increasing temperature decreased the performance of US, US-H2O2, and US-IO4- systems, while it could increase the degradation of BPA in US-S2O82- and US-HSO5-. The activation energy for BPA decomposition using the US-IO4- system was the lowest, at 0.453nullkJnullmol-1, and the synergy index was the highest at 2.22. Additionally, the ΔG# value was found to be 2.11 + 0.29T when the temperature ranged from 25 °C to 45 °C. The main oxidation contribution is achieved by hydroxyl radicals in scavenger test. The mechanism of activation of US-oxidant is heat and electron transfer. In the case of the US-IO4- system, the economic analysis yielded 271 kwh m-3, which was approximately 2.4 times lower than that of the US process.

Zero-valent iron based materials selection for permeable reactive barrier using machine learning.

The zero-valent iron (ZVI) based reactive materials are potential remediation reagents in permeable reactive barriers (PRB). Considering that reactive materials is the essential to determining the long-term stability of PRB and the emergence of a large number of new iron-based materials. Here, we present a new approach using machine learning to screen PRB reactive materials, which proposes to improve the efficiency and practicality of selection of ZVI-based materials. To compensate for the insufficient amount of existing machine learning source data and the real-world implementation, machine learning combines evaluation index (EI) and reactive material experimental evaluations. XGboost model is applied to estimate the kinetic data and SHAP is used to improve the accuracy of model. Batch and column tests were conducted to investigate the geochemical characteristics of groundwater. The study find that specific surface area is a fundamental factor correlated with the kinetic constants of ZVI-based materials, according to SHAP analysis. Reclassifying the data with specific surface area significantly improved prediction accuracy (reducing RMSE from 1.84 to 0.6). Experimental evaluation results showed that ZVI had 3.2 times higher anaerobic corrosion reaction kinetic constants and 3.8 times lower selectivity than AC-ZVI. Mechanistic studies revealed the transformation pathways and endpoint products of iron compounds. Overall, this study is a successful initial attempt to use machine learning for selecting reactive materials.

Evaluation of anode materials in sonoelectrochemistry processes: Kinetic, mechanism, and cost estimation.

Eco-friendly pollutant treatment technology has a developing tendency in future. The combination of ultrasound (US) and electrochemical (EC) is a promising technology, because they are efficient, clean and environmentally friendly. In this study, the impacts of anode material have been investigated in US (300 kHz) and EC (10V) system. The results of all systems revealed that the kinetic constant decreased with increasing pH. The results are also shown that ΔG# > 0 and ΔH# > 0 during PCP degradation in EC or US-EC systems are non-spontaneous and endothermic reactions. Meanwhile, in the US-EC system, TiO2, Ti4O7, PbO2, SnSb, RuIr, and BDD, except for TiO2, all the anode materials showed a synergistic index (SI) of 106-197%, and the activation energies were 19.32, 33.4, 33.74, 32.84, 10.41, 36.44 kJ mol-1, respectively. In EC and US-EC systems, PCP can be completely mineralized by BDD anode within 30 min. TBA scavenger experiments verified that hydroxyl radicals were the main oxidant in each system using BDD and PbO2 anode. As a result of estimating the cost according to the anode material when removing PCP using the EC or US-EC system, BDD was the smallest in the two systems, 1.58 and 1.12 $ m-3, respectively. Finally, this study may serve as a reference for implementation of US-EC system in wastewater treatment.

Evaluation of self-oxidation and selectivity of iron-based reductant in anaerobic pentachlorophenol contaminated soil.

Soil contamination due to chlorinated organics prompts an important environmental problem; however, the iron-based reduction materials and complicated ground environment are the main barriers to implementation and promotion of in situ soil remediation. Therefore, this study aims to evaluate the reductants zero-valent iron (ZVI) and its activated carbon composite (AC-ZVI) in terms of their self-oxidation and selectivity in soil experiments. The results indicated that saturated moisture conditions were beneficial for degradation due to the dispersal of the pollutants from soil particles. Particularly, increasing the water/soil ratio to the over-saturated state would decrease the selectivity of ZVI and AC-ZVI. Meanwhile, increasing the reductant loading decreased the selectivity of ZVI and AC-ZVI, whereas the high initial concentration increased the selectivity of AC-ZVI. In addition, the self-oxidation of ZVI (3.0 ×10-3 h-1) is 4.2 times higher than that of AC-ZVI (0.7 ×10-3 h-1), and the selectivity of AC-ZVI (48%) is 6.9 times higher than that of ZVI (7%), which confirmed that AC-ZVI is a superior iron-based amendment in saturated moisture conditions. Therefore, this study provides a reliable and feasible evaluation method for in situ remediation process, and deepens the understanding of the effects of moisture contents.

Arsenic adsorption study in acid mine drainage using fixed bed column by novel beaded adsorbent.

The downflow fixed-bed column adsorption-desorption of arsenic by the beaded coal mine drainage sludge-Youngdong (BCMDS-YD) adsorbent was experimentally studied. The specific surface area of BCMDS-YD synthesized using inorganic binding was 178 m2 g-1, and the pHIEP was 5.32. The XRD analysis revealed that it was composed of calcite and schwertmannite. As a result, an increase in the inflow rate resulted in an earlier column exhaustion. The breakthrough curve indicated that a smaller adsorbent particle size and lower influent pH prolonged the column life span. Thomas logistic model was applied to fit the breakthrough curve by linear and nonlinear regression. Under the condition of an influent flow rate of 2.65 mL min-1 (EBCT 40 min), an influent arsenic average concentration of 0.5-1 mg L-1, an influent pH of 7.6, an adsorbent mass of 100 g, an adsorbent grain size of 1.40-1.70 mm, and an operating temperature of 25 °C, the equilibrium adsorption capacity reached 4.56 mg g-1. The mechanism of arsenic adsorption is adsorption and precipitation. As a result of the adsorbent reuse experiment, it was judged that it could be reused with good results in all three cycle experiments. The cost of treating arsenic with the BCMDS-YD adsorbent was 0.145 $ per m-3. The results of this study show examples of sustainable development concepts in mining drainage, and BCMDS-YD can effectively remove arsenic and other heavy metals from acid mine drainage.

Quantification of perfluorooctanoic acid decomposition mechanism applying negative voltage to anode during photoelectrochemical process.

Perfluorooctanoic acid (PFOA) is a carcinogen with a high binding energy between fluorine and carbon and is symmetrically linked, making it difficult to treat. In this study, a self-doped TiO2 nanotube array (TNTA) was used as the anode and platinum as the cathode to quantify the PFOA removal mechanism using a photoelectrochemical (PEC) system. The external voltage was negative compared to that of the anode. In addition, NO3- and t-BuOH were used as scavengers to quantify the PFOA oxidation/reduction mechanism in the PEC system. As a result of the study, TNTA crystals are TiO2 anatase, and the band gap energy was 3.42. The synergy index of PEC was 1.25, and the best electrolyte was SO42-. The PFOA decomposition activation energy corresponds to 70.84 kJ mol-1. Moreover, ΔH# and ΔS# correspond to 68.34 kJ mol-1 and 0.190 kJ mol-1 K-1, respectively. When the external negative voltage was 1 V, the contributions of the oxidation/reduction reaction during PFOA decomposition were 60% and 40%, and when the external negative voltage was 5 V, the contributions of the redox reaction were 45% and 55%. As the external negative voltage increased, the contribution of the reduction reaction increased as the number of electrons applied to the anode increased. When PFOA was decomposed, the by-products were C7F13O2H, C6F11O2H, C5F9O2H, and C4F7O2H, respectively. This study is expected to be used as basic data for research on the effects of other factors on the oxidation/reduction as well as the selection of anode and cathode materials on the decomposition of pollutants other than PFOA when using a PEC system.

Rare earth real wastewater treatment by pilot scale using new concept continuous treatment process.

Rare earth (RE) containing radioactive species and a variety of toxic pollutants The treatment of real wastewater is very important for environmental protection. In this study, a new concept of continuous process consisting of precipitation, adsorption, and oxidation was developed without the use of chemicals. In the sedimentation step, waste oyster shell(WOS) and a PE tube diffuser(PE250) containing Na2S (PECa/S), PECa/S were prepared, which were used to precipitate heavy metals with a removal efficiency of 97% or more. In the adsorption step, fluorine (F), arsenic (As), and thorium (Th) were precipitated and removed when heavy metals were removed using coal mine drainage sludge (CMDS) and an adsorbent (PUCMDS) made of polyurethane (PU). Running a semi and pilot scale continuous process using PECa/S, PUCMDS and O3/HC systems resulted in a semi and pilot scale operating period of 120 and 62 days, and 60.26, 797.84, 46.94, 78.62 g, and 7.120 kg and 266.35, 42556.8, 191.95, 3108.43 g and 629.84 kg for As, F, Th, Pb and CODcr has been removed respectively. In addition, the removal efficiencies of As, F, Th, Pb and CODcr were 99.75, 99.98, 93.60, 99.99, and 88.82%, respectively, when treating real RE wastewater using the pilot scale system. Without the use of agitated reactors and regulators, the new concept of continuous process can effectively treat RE real wastewater, and the quality of the process outlet has met the pollutant limits recommended by EPA and China for irrigation.

Evaluation of stabilizing material and stabilization efficiency through comparative study of toxic heavy metal transfer between corn and peanut grown in stabilized field soil.

Soil contaminated with toxic heavy metals (THMs) was stabilized by adding a combination of waste resources in 7.0 wt%, including coal-mine drainage sludge, waste cow bone, and steelmaking slag, in the ratio of 5:35:60. Subsequently, corn and peanut were cultivated in treated soil to investigate the effects of the waste resources on THM mobility in soil and translocation to plants. Sequential extraction procedures (SEP) was used to analyze mobile phase THMs which could be accumulated in the plants. SEP shows that mobile Pb, Cd, Cu, Zn, Ni, Cr, and As were reduced by 8.48%, 29.22%, 18.85%, 21.66%, 4.58%, 62.78%, and 20.01%, respectively. The bioaccumulation of THMs was clearly hindered by stabilization; however, the increment in the amount of immobile-phase THMs and change in the amount of translocated THMs was not proportional. The corn grains grown above the soil surface were compared with the peanut grains grown beneath the soil surface, and the results indicating that the efficiency of stabilization on THM translocation may not depend on the contact of grain to soil but the nature of plant. Interestingly, the results of bioaccumulation with and without stabilization showed that the movement of some THMs inside the plants was affected by stabilization.

Arsenic adsorption on two types of powdered and beaded coal mine drainage sludge adsorbent.

The aim of this study was to evaluate the performance of a new adsorbent in terms of beading the sludge generated from coal mine drainage or arsenic removed from water is treated by electro-purification (EP) and chemical-precipitation (CP) methods. Batch experiments were conducted to study the influence of experimental parameters such as pH and temperature, as well as the mechanism of arsenic adsorption with the new adsorbent. The porosity of coal mine drainage sludge (CMDS)-beaded adsorbent made of chitosan and alginate was optimized by adding NaHCO3 powder to generate CO2 gas during the preparation process. Two types of adsorbents, beaded EP Najeon CMDS (BCMDSEP-NJ) and beaded CP Yeongdong CMDS (BCMDSCP-YD), were prepared by heating. The specific surface areas of the powdered adsorbents CMDSEP-NJ and CMDSCP-YD were 104 and 231 m2 g-1, respectively. The prepared beaded adsorbents BCMDSEP-NJ and BCMDSCP-YD had good porosity and specific surface areas of 16.8 and 21.2 m2 g-1, respectively. The X-ray diffraction results showed that the structure was goethite (aragonite) and schwertmannite. The pseudo second-order, intra-particle, and Langmuir models were used to explain the adsorption process. The qmax values of As(III) with BCDMSEP-NJ and BCMDSCP-YD adsorbents are 4.31 and 4.58 mg g-1, respectively and those of AS(V) are 9.31 and 10.93 mg g-1, respectively. The adsorption capacity for As(III) increased with increasing pH, whereas that for As(V) decreased. The activation energy was 8 kJ mol-1 or more. The mechanism of adsorption of arsenic using a beaded adsorbent was chemical adsorption followed by diffusion. The results of the present study suggest that new adsorbents can be effectively utilized for arsenic removal from water.

Improving sono-activated persulfate oxidation using mechanical mixing in a 35-kHz ultrasonic reactor: Persulfate activation mechanism and its application.

This study investigated the degradation of ibuprofen (IBP), an activated persulfate (PS), when subjected to ultrasonic (US) irradiation and mechanical mixing (M). The effects of several critical factors were evaluated, including the effect of rpm on M, PS concentration, and initial pH, and that of temperature on IBP degradation kinetics and the PS activation mechanism. The resulting IBP oxidation rate constant was significantly higher at 400 rpm. As the PS load increased, the IBP oxidation rate constant increased. The value of the IBP reaction rate increased with decreasing pH; below pH 4.9, there was no significant difference in the IBP oxidation rate constant. The IBP oxidation activation energy when using the US/M-PS system was 18.84 kJ mol-1. In the US/M-PS system, PS activation was the primary effect of temperature at the interface during the explosion of cavitation bubbles. These encouraging results suggest that the US-PS/M process is a promising strategy for the treatment of IBP-based water pollutants.

Application of persulfate with hydrodynamic cavitation and ferrous in the decomposition of pentachlorophenol.

Hydrodynamic cavitation (HC) and Fe(II) are advanced oxidation processes, in which pentachlorophenol (PCP) is treated by the redox method of activating persulfate (PS). The kinetics and mechanism of the HC and Fe(II) activation of PS were examined in aqueous solution using an electron spin resonance (ESR) spin trapping technique and radical trapping with pure compounds. The optimum ratio of Fe(II)/PS was 1:2, and the hydroxyl radical (HO) and sulfate radical (SO4-) generation rate were 5.56 mM h-1 and 8.62 µM h-1, respectively. The generation rate and Rct of HO and SO4- at pH 3 and 50 °C in the Fe(II)/PS/HC system are 7584.6 µM h-1, 0.013 and 24.02 µM h-1, 3.95, respectively. The number of radicals was reduced as the pH increased, and it increased with increasing temperature. The PCP reaction rate constants was 4.39 × 10-2 min-1 at pH 3 and 50 °C. The activation energy was 10.68 kJ mol-1. In addition, the mechanism of PCP treatment in the Fe(II)/PS/HC system was a redox reaction, and the HO-/SO4- contribution was 81.1 and 18.9%, respectively. In this study, we first examined PCP oxidation through HO and SO4- quantification using only the Fe(II)/PS/HC process. Furthermore, the results provide the foundation for activation of PS by HC and Fe(II), but also provide a data basis for similar organic treatments other than PCP.

Development of modified mesoporous carbon (CMK-3) for improved adsorption of bisphenol-A.

The adsorption of bisphenol-A (BPA) on ordered mesoporous carbon (CMK-3) and modified CMK-3 (MCMK-3) for decontamination of aqueous medium was investigated. The CMK-3 and MCMK-3 materials had uniform pore sizes of 3.60 and 3.70 nm and high Brunauer-Emmett-Teller (BET) surface areas of 751 and 564 m2 g-1, respectively. The maximum adsorption capacities of CMK-3 and MCMK-3 were 178.57 (0.24 mg m-2) and 238.01 (0.42 mg m-2) mg g-1, respectively at 298 K (pH 6.4). The difference in the adsorption capacities is attributed to the specific surface area and hydrophobicity of the adsorbents. The adsorption of BPA on CMK-3 and MCMK-3 may be influenced by π-π bonding and hydrophobic and electrostatic interactions, and the excellent adsorption capacity of MCMK-3 is attributed to its unique sp2-hybridized single-atom-layer structure. The kinetics and isotherm data were described by the pseudo-second order kinetic model and the Langmuir isotherm, respectively. This difference in the adsorption kinetics of CMK-3 and MCMK-3 is caused by the increase in the pore diameter of the latter. Further, CMK-3 and MCMK-3, with an open geometry consisting of interlinked nanorods, allow for faster intraparticle diffusion. Overall, CMK-3 and MCMK-3 could be promising adsorbents for the removal of chemicals containing benzene rings from wastewater.

Hybrid reactor based on hydrodynamic cavitation, ozonation, and persulfate oxidation for oxalic acid decomposition during rare-earth extraction processes.

A cost-effective method for treating oxalic acid (OA) during rare-earth extraction was developed using hydrodynamic cavitation (HC), ozone (O3), and persulfate (PS) (HC@PS@O3 process). The results showed that the optimal inlet pressure during HC was 5.10 kg cm-2 with an orifice plate diameter of 2 mm. Moreover, HC was shown to activate PS, providing an alternative activation method to base or heat as an ultrasound activation method for chemical oxidation. O3 was also shown to activate PS. For OA oxidation using the HC@PS@O3 process, the optimum pH was 3 and the reaction rate increased with increasing temperature. Further, the activation energy was 36.69 kJ mol-1. The mechanisms unveiled in this study will allow optimization of the HC@PS@O3 process as a chemical oxidation technology. The kinetic investigation and economic evaluation of the HC@PS@O3 process can be used as the basis for real wastewater treatment processes in the future.

Application of pea-like yolk-shell structured Fe3O4@TiO2 nanosheets for photocatalytic and photo-Fenton oxidation of bisphenol-A.

Uniform pea-like yolk-shell (PLYS) structured magnetic TiO2(PLYS-Fe3O4@TiO2) nanosheets have been prepared via a combined kinetics-controlled mechanical force-driven and hydrothermal etching assisted crystallization method and characterized. The resulting PLYS-Fe3O4@TiO2 nanosheets possess well defined yolk-shell structures with a large BET surface area (∼187.26 m2 g-1) and a strong magnetic susceptibility (∼17.4 emu g-1). The reaction rate constant was 24.2 × 10-2 min-1 as a result of oxidative decomposition of BPA using UV/PLYS-Fe3O4@TiO2/H2O2 system. This is 1.1 and 8.34 times faster than the BPA decomposition reaction rate constant in UV/TiO2/H2O2 and UV/Fe3O4/H2O2 systems, respectively. The synthesized catalyst also exhibited excellent recycle capability and excellent acid decomposition performance.

Degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans in real-field soil by an integrated visible-light photocatalysis and solvent migration system with p-n heterojunction BiVO4/Bi2O3.

Degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in real-field soil was conducted using an integrated photocatalysis-solvent migration system of BiVO4/Bi2O3 and n-hexane. The photocatalyst BiVO4/Bi2O3 was synthesized, and its performance was found to be affected by the BiVO4 content, with 20wt% BiVO4 showing the best performance owing to its p-n heterojunction being well formed. Migration was affected by the amount of n-hexane, with 15% n-hexane giving the most effective transportation of PCDD/Fs. 37.2% of 17 PCDD/Fs was removed in 60h by the integrated photocatalysis-solvent migration system, although the reaction zone covered 8.5% of the volume of the soil. The result showed that migration via n-hexane fulfilled the aim of carrying contaminants from inside of the soil to the surface. Electron-scavenging experiments with BiVO4/Bi2O3 showed an 18.4% of performance in removal compared to no-scavenging condition, which showed that the main reactions driving BiVO4/Bi2O3 visible-light photocatalysis for aryl-chloride were found to be reduction-based. Owing to the hindering effect of Cl atoms, degradation by hydroxyl radical could proceed after initial dechlorination. This study establishes the applicability of integrated photocatalysis-solvent migration systems in real-field settings, and is the first report of a visible-light photocatalyst, BiVO4/Bi2O3, for the degradation of PCDD/Fs in soil.

Synthesis, characterization and sonocatalytic applications of nano-structured carbon based TiO2 catalysts.

In order to enhance sonocatalytic oxidation of a recalcitrant organic pollutant, rhodamine B (RhB), it is necessary to study the fundamental aspects of sonocatalysis. In this study, TiO2-incorporated nano-structured carbon (i.e., carbon nanotubes (CNTs) or graphene (GR)) composites were synthesized by coating TiO2 on CNTs or GR of different mass percentages (0.5, 1, 5, and 10 wt%) by a facile hydrothermal method. The sonocatalytic degradation rates of RhB were examined for the effect of ultrasound (US) frequency and calcination temperature by using the prepared TiO2-NSC composites. Since US frequency affected the sonoluminescence (SL) intensities, it was proposed that there exists a correlation between the surface area or band-gap of the sonocatalysts and the degradation kinetic constants of RhB. In addition, the reusability of TiO2-GR composites was also investigated. Overall, the performance of TiO2-GRs prepared by the hydrothermal method was better than that of calcined TiO2-CNTs. Among TiO2-GRs, 5% GR incorporated media (TiO2-GR-5) showed the best performance. Interestingly, the kinetic constants of sonocatalysts prepared under hydrothermal conditions had a negative linear relationship with the band-gap energy for the corresponding media. Furthermore, the strongest SL intensity and highest degradation rates of RhB for both carbonaceous composites were observed at 500 kHz. The kinetic constants of calcined media decreased linearly as the specific area of the media decreased, while the band-gap energy could not be correlated with the kinetic constants. The GR combined TiO2 composite might be a good sonocatalyst in wastewater treatment using ultrasound-based oxidation because of its high stability.

Magnetic Pd@Fe3O4 composite nanostructure as recoverable catalyst for sonoelectrohybrid degradation of Ibuprofen.

In the present research, the degradation of an emerging pharmaceutical micro-pollutant, Ibuprofen (IBP) by using Pd@Fe3O4 and a hybrid sono-electrolytical (US/EC) treatment system has been demonstrated for the first time. The magnetically separable nanocomposite, Pd@Fe3O4 catalyst was synthesized following co-precipitation method to enhance the efficiency of US/EC system. The synthesized catalyst showed a strong reusable property even after applying for five times and in all the five cases, 100% degradation of IBP was maintained. It not only enhanced the IBP degradation rate, but also reduced the energy consumption of the system by ∼35%. Its strong magnetization value of 64.27emug-1 made it easily separable. Hence, a comprehensive knowledge on the application of combined energy based US/EC system and magnetically separable multifunctional catalysts for degradation of intractable pollutants like Ibuprofen was achieved, assuring that US/EC can be an effective option for IBP treatment.

A novel sequential process for remediating rare-earth wastewater.

A novel and economic sequential process consisting of precipitation, adsorption, and oxidation was developed to remediate actual rare-earth (RE) wastewater containing various toxic pollutants, including radioactive species. In the precipitation step, porous air stones (PAS) containing waste oyster shell (WOS), PASWOS, was prepared and used to precipitate most heavy metals with >97% removal efficiencies. The SEM-EDS analysis revealed that PAS plays a key role in preventing the surface coating of precipitants on the surface of WOS and in releasing the dissolved species of WOS successively. For the adsorption step, a polyurethane (PU) impregnated by coal mine drainage sludge (CMDS), PUCMDS, was synthesized and applied to deplete fluoride (F), arsenic (As), uranium (U), and thorium (Th) that remained after precipitation. The continuous-mode sequential process using PAS(WOS), PU(CMDS), and ozone (O3) had 99.9-100% removal efficiencies of heavy metals, 99.3-99.9% of F and As, 95.8-99.4% of U and Th, and 92.4% of COD(Cr) for 100 days. The sequential process can treat RE wastewater economically and effectively without stirred-tank reactors, pH controller, continuous injection of chemicals, and significant sludge generation, as well as the quality of the outlet met the EPA recommended limits.