Photo-electrochemical Osmotic System Enables Simultaneous Metal Recovery and Electricity Generation from Wastewater.

Global depletion of natural resources provides an impetus for developing low-cost, environmentally benign technologies for the recovery of valuable resources from wastewater. In this study, we present an autonomous photo-electrochemical osmotic system (PECOS) that can recover a wide range of metals from simulated metal-laden wastewater with sunlight illumination while generating electricity. The PECOS comprises a draw solution chamber with a nickel nanoparticle-functionalized titanium nanowire (Ni-TiNA) photoanode, a feed solution chamber containing synthetic wastewater with an immersed carbon fiber cathode, and a forward osmosis (FO) membrane mounted between the chambers as a separator. Using a Na2-EDTA anolyte as a draw solution at neutral pH, we demonstrate that a sunlit PECOS achieves copper recovery at a rate of 51 g h-1 per m-2 of membrane area from simulated copper-laden wastewater while simultaneously producing a maximum power density of 228 mW m-2. Moreover, because of the osmotic pressure difference generated by the photo-electrochemical reactions, the PECOS reduces the wastewater volume by extracting fresh water through the FO membrane at a water flux of 0.84 L m-2 h-1. We further demonstrate the feasibility of the PECOS in recovering diverse metals from a simulated metal-laden industrial wastewater under sunlight irradiation. Our proof-of-concept PECOS prototype provides a sustainable technological solution that leverages sunlight in an electrochemical osmotic system to recover multiple resources from wastewater.

Enhanced Photocatalytic Water Decontamination by Micro-Nano Bubbles: Measurements and Mechanisms.

Despite recent advancements in photocatalysis enabled by materials science innovations, the application of photocatalysts in water treatment is still hampered due to low overall efficiency. Herein, we present a TiO2 photocatalytic process with significantly enhanced efficiency by the introduction of micro-nano bubbles (MNBs). Notably, the removal rate of a model organic contaminant (methylene blue, MB) in an air MNB-assisted photocatalytic degradation (PCD) process was 41-141% higher than that obtained in conventional macrobubble (MaB)-assisted PCD under identical conditions. Experimental observations and supporting mechanistic modeling suggest that the enhanced photocatalytic degradation is attributed to the combined effects of increased dissolution of oxygen, improved colloidal stability and dispersion of the TiO2 nanocatalysts, and interfacial photoelectric effects of TiO2/MNB suspensions. The maximum dissolved oxygen (DO) concentration of the MNB suspension (i.e., 11.7 mg/L) was 32% higher than that of an MaB-aerated aqueous solution (i.e., 8.8 mg/L), thus accelerating the hole oxidation of H2O on TiO2. We further confirmed that the MNBs induced unique light-scattering effects, consequently increasing the optical path length in the TiO2/MNB suspension by 7.6%. A force balance model confirmed that a three-phase contact was formed on the surface of the bubble-TiO2 complex, which promoted high complex stability and PCD performance. Overall, this study demonstrates the enhanced photocatalytic water decontamination by MNBs and provides the underlying mechanisms for the process.

Evolution of dissolved organic matter during artificial groundwater recharge with effluent from underutilized WWTP and the resulting facilitated transport effect.

Currently, the interaction between contaminants and dissolved organic matter (DOM) during artificial groundwater recharge (AGR) with effluent from underutilized wastewater treatment plant (WWTP) is unclear. The present study investigated DOM evolution in this AGR scenario. The DOM composition in the inflow was identified to be distinct to that of the outflow due to the release of soil humic acid (HA). The soluble soil HA was then extracted and used in co-transport experiments with tetracycline (TC). The separated HA transport through the soil column exhibited high mobility with mass recovery >92.5% in the effluent. Following the mixing of injected TC and HA, the TC breakthrough in the column increased with HA concentration. TC was heavily adsorbed by the soil without the presence of HA, yet the retention ratios decreased from 63.60% to 53.30% for the HA range of 0-20 mg L-1. An advection-dispersion-retention (ADR) numerical model was developed to effectively quantify the HA-TC co-transport, with results demonstrating the reduction in the TC attachment rate with increasing HA concentrations. Furthermore, batch adsorption experiments, kinetics and isotherms models, and FTIR spectra analysis were implemented to determine the underlying mechanism. The co-transport behavior was observed to be a function of the relative soil sorption affinity between HA and TC. The weaker sorption of the HA-coated TC compared to the separated TC consequently suggests that HA is likely to compete for available soil adsorption sites. Thus, the release of soil humus during AGR can potentially facilitate the transport of the introduced contaminants.

Stepwise extraction of Fe, Al, Ca, and Zn: A green route to recycle raw electroplating sludge.

Electroplating sludge is a hazardous waste produced in large quantities in the electroplating industry during production. It is rich in heavy metal resources and can be recovered as value-added heavy metal products. To recover Zn in electroplating sludge, Fe/Al/Ca impurities were effectively removed as hematite, boehmite, and calcium sulfate, respectively, via a facile hydrothermal method with reduction of nitric acid by addition of glucose. After the sludge was dissolved in nitric acid, the generated solution contained 6.1 g/L of Zn, 2.2 g/L of Fe, 2.5 g/L of Al, and 2.9 g/L of Ca. First, approximately 100% Fe was extracted as hematite nanoparticles containing 94.6 wt% Fe2O3 after the solution was treated at 190 °C for 6 h. Second, when the temperature was elevated to 270 °C, nearly 99% Al was isolated as boehmite particles containing 95.2 wt% Al2O3. Third, more than 98% Ca was removed as anhydrite, which contained 95.9 wt% CaSO4, by adding sulfuric acid. During the steps, the total loss of Zn was less than 3%, and 5.75 g/L of residual Zn was recovered as zincite containing 92.2 wt% ZnO by adjusting the pH to 8. The dissolved Fe, Al, and Ca impurities were successfully removed as purified hematite, boehmite, and anhydrite, respectively, through the stepwise separation method by adjusting reaction temperatures and pH. The high content of Zn in the electroplating sludge was finally purified as zincite.

Electrochemical-Osmotic Process for Simultaneous Recovery of Electric Energy, Water, and Metals from Wastewater.

A highly-efficient, autonomous electrochemical-osmotic system (EOS) is developed for simultaneous recovery of electric energy, water, and metals from wastewater. We demonstrate that the system can generate a maximum electric power density of 10.5 W m-2 using a spontaneous Fe/Cu2+ galvanic cell, while simultaneously achieving copper recovery from wastewater. With an osmotic pressure difference generated by the deployed electrochemical reactions, water is osmotically extracted from the feed solution with the EOS at a water flux of 5.1 L m-2 h-1. A scaled-up EOS realizes a power density of 105.8 W per m-3 of treated water to light an LED over 24 h while also enhancing water extraction and metal recovery. The modularized EOS obtains ultrahigh (>97.5%) Faradaic efficiencies under variable operating conditions, showing excellent system stability. The EOS is also versatile: it can recover Au, Ag, and Hg from wastewaters with simultaneous electricity and water coproduction. Our study demonstrates a promising pathway for realizing multiresource recycling from wastewater by coupling electrochemical and osmosis-driven processes.

Risk of physical clogging induced by low-density suspended particles during managed aquifer recharge with reclaimed water: Evidences from laboratory experiments and numerical modeling.

How to reduce the risk of physical clogging is the most significant challenge during managed aquifer recharge (MAR). The prediction of occurrence and development of physical clogging has received increasing attention. In this study, chlorinated secondary wastewater (SW) was recharged into a laboratory column filled with quartz sands. The results showed that the continuous injection of reclaimed water caused a significant reduction in hydraulic conductivity by about 86% in porous media, during the 50-h injection process. The reduction was attributed to physical clogging resulting from the deposition of suspended particles with a flocculent and reticular structure, significantly increasing the surface area and the effective volume of the particle deposits. A numerical model was established based on the mass balance equations for liquid and suspended particles, coupling the particle transport-deposition model and the expressions describing the relationships between the porosity, hydraulic conductivity (K), and the concentration of deposited particles; the model was used to obtain a quantitative description of the temporal and spatial distribution of physical clogging. The bulk factor and the attachment and detachment coefficients were calibrated simultaneously. The model results provided an improved understanding of the influence degree of the three parameters on the physical clogging process. The sensitivity analysis results showed that the bulk factor had the largest sensitivity among the three parameters. In addition, a significant correlation was observed between the simulated data and the experimental data (R2 > 0.90, p < 0.01). The proposed numerical model provides a meaningful guidance tool for assessing and predicting the risk of physical clogging induced by low-density floc particles during artificial recharge with reclaimed water at a large-scale site.

Novel application of a Z-scheme photocatalyst of Ag3PO4@g-C3N4 for photocatalytic fuel cells.

A composite of Ag3PO4@g-C3N4 with the Z-scheme structure was synthesized, and used as the photoanode in a photocatalytic fuel cell (PFC). With the help of the Z-scheme design, both the degradation of tetracycline and the output of maximum power density (Pmax) were greatly enhanced in this PFC system. The degradation rate of tetracycline in the Ag3PO4@g-C3N4 PFC was 2.53 times and 3.65 times that in the PFC systems with the Ag3PO4 photoanode and the g-C3N4 photoanode, respectively. The Pmax of the Ag3PO4@g-C3N4 PFC was 6.06 µW cm-2, which was 1.46 times and 90.4 times that of the Ag3PO4 PFC (4.16 µW cm-2) and the g-C3N4 PFC (0.067 µW cm-2), respectively. The possible mechanism was proposed. The Z-scheme photoanode could not only contribute to the separation of photogenerated carriers to achieve a high photocatalytic activity, but also reserve a good redox capacity. Additionally, aeration played an important role on the PFC performance. It was demonstrated that N2 purging facilitated the electricity generation, while O2 purging promoted the pollutant degradation.

Responses to copper stress in the metal-resistant bacterium Cupriavidus gilardii CR3: a whole-transcriptome analysis.

Microbial metal-resistance mechanisms are the basis for the application of microorganisms in metal bioremediation. Despite the available studies of bacterial molecular mechanisms to resistance metals ions (particularly copper), the understanding of bacterial metal resistance is very limited from the transcriptome perspective. Here, responses of the transcriptome (RNA-Seq) was investigated in Cupriavidus gilardii CR3 exposed to 0.5 mM copper, because strain CR3 had a bioremoval capacity of 38.5% for 0.5 mM copper. More than 24 million clean reads were obtained from six libraries and were aligned against the C. gilardii CR3 genome. A total of 310 genes in strain CR3 were significantly differentially expressed under copper stress. Apart from the routine copper resistance operons cus and cop known in previous studies, Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses of differentially expressed genes indicated that the adenosine triphosphate-binding cassette transporter, amino acid metabolism, and negative chemotaxis collectively contribute to the copper-resistant process. More interestingly, we found that the genes associated with the type III secretion system were induced under copper stress. No such results were reordered in bacteria to date. Overall, this comprehensive network of copper responses is useful for further studies of the molecular mechanisms underlying responses to copper stress in bacteria.

Valorization of manganese-containing groundwater treatment sludge by preparing magnetic adsorbent for Cu(II) adsorption.

Mn-containing sludge from groundwater treatment was converted to magnetic particles (MPs) via a one-step hydrothermal method using sodium ascorbate (SA) as the reductant. The MPs were characterized by X-ray diffraction spectroscopy, Mössbauer spectroscopy, X-ray fluorescence spectroscopy, magnetometry and Gran titration and the results showed that magnetic jacobsite was obtained as an intermediate product in transformation of Fe/Mn oxides to siderite and rhodochrosite. When the molar ratio of SA to Mn in the sludge was two, the produced MPs-2 contained a mixture of ferrihdyrite, hematite, jacobsite and Si/Al oxides, and could magnetize at 2.4 emu/g. Ferrihydrite content in MPs decreased with increase of the SA/Mn molar ratio, leading to decrease of the surface sites concentration (Hs). Thus, MPs-2 contained optimized Hs of 6.7 mmoL/g and a desirable adsorption capacity of Cu(II) (73.1 mg/g). The adsorption isotherms of MPs-2 on Cu(II) complied with the Langmuir model and the adsorption kinetics fitted well with the pseudo-second-order model. The major mechanism of adsorption was cationic exchange of the coordinated H and Na ions on MPs-2 surface sites with the Cu(II) ions. This study was the first time to report preparation of MPs by recycling Mn-containing sludge, which could be used as a high-capacity and low-cost adsorbent in treatment of heavy metal-containing wastewater.

Coupling heavy metal resistance and oxygen flexibility for bioremoval of copper ions by newly isolated Citrobacter freundii JPG1.

The potential for bioremoval of copper ions was investigated by a novel strain of bacterium Citrobacter freundii JPG1, which was newly isolated from gold mining tailing in China and grew either aerobically or anaerobically. The strain cross-tolerated heavy metals of Ag+, Cd2+, Co2+, Cr6+, Cu2+ and Ni2+ and removed copper under both aerobic and anaerobic conditions with the stress of copper. Under aerobic conditions, the cells grew rapidly and exhibited higher biomass at low copper concentrations (<1 mmol L-1), while the growth of cells was almost completely inhibited at high copper concentrations (2 mmol L-1). However, the cell growths were less affected by copper under anaerobic conditions. Similarly, the copper-removal efficiency was affected by oxygen and the capability of copper removal by anaerobic cells was significantly higher than that of aerobic cells (P < 0.05). The quantitative measurement of extracellular biosorption and intercellular bioaccumulation of copper indicated that biosorption efficiencies for aerobic cells (37%) and anaerobic cells (38%) were similar but the bioaccumulation by anaerobic cells was almost ten-fold higher than that by aerobic cells, indicating bioaccumulation contributed most in copper reduction under anaerobic conditions. Overall, the results suggested the facultative strain C. freundii JPG1 had great potential in the treatment of copper-laden industrial wastewater under both aerobic and anaerobic conditions.

Characterization of a novel micro-pressure swirl reactor for removal of chemical oxygen demand and total nitrogen from domestic wastewater at low temperature.

A novel micro-pressure swirl reactor (MPSR) was designed and applied to treat domestic wastewater at low temperature by acclimating microbial biomass with steadily decreasing temperature from 15 to 3 °C. Chemical oxygen demand (COD) was constantly removed by 85% and maintained below 50 mg L-1 in the effluent during the process. When the air flow was controlled at 0.2 m3 h-1, a swirl circulation was formed in the reactor, which created a dissolved oxygen (DO) gradient with a low DO zone in the center and a high DO zone in the periphery for denitrification and nitrification. 81% of total nitrogen was removed by this reactor, in which ammonium was reduced by over 90%. However, denitrification was less effective because of the presence of low levels of oxygen. The progressively decreasing temperature favored acclimation of psychrophilic bacteria in the reactor, which replaced mesophilic bacteria in the process of treatment.

Characteristics and kinetics simulation of controlled-release KMnO4 for phenol remediation.

Controlled-release KMnO4 (CRP) technology has been recently developed as an improved, highly efficient technique in wastewater treatment. In this study, batch-style experiments were conducted to evaluate this technology. The release characteristics of CRP in distilled water and the reaction between CRP and phenol were studied and fitted using MATLAB software. Results indicated that in distilled water, temperature (T) and pH value had a larger effect than dissolved oxygen (DO) concentration on the release characteristics of KMnO4, and this relationship can be accurately described by the following kinetic equation: logQ = log[1.141T(0.152)(pH)(-1.0536)(DO)(0.4674)] + [0.0048T(0.3756)(pH)(1.8854)(DO)(-0.0509)]logt. KMnO4 released from CRP can effectively degrade phenol-contaminated water with different concentrations. A simulated equation (r = -dCA/dt = -15.1705 CA(0.6840)CP(-0.1406)) characterizing phenol degradation was developed using MATLAB software. Comparison between the theoretical phenol removal rates deduced by the above two equations and the initial phenol concentration as well as the CRP dosage with the experimental data indicates that the differences between them were less than 20%. The results indicate phenol can be effectively removed by CRP and smaller dosage of KMnO4 was required compared with literature values. The models can provide guidance for CRP application in real polluted sites, which can lower the cost for site remediation.

Intimate Coupling of Photocatalysis and Biodegradation for Degrading Phenol Using Different Light Types: Visible Light vs UV Light.

Intimate coupling of photocatalysis and biodegradation (ICPB) technology is attractive for phenolic wastewater treatment, but has only been investigated using UV light (called UPCB). We examined the intimate coupling of visible-light-induced photocatalysis and biodegradation (VPCB) for the first time. Our catalyst was prepared doping both of Er(3+) and YAlO3 into TiO2 which were supported on macroporous carriers. The macroporous carriers was used to support for the biofilms as well. 99.8% removal efficiency of phenol was achieved in the VPCB, and this was 32.6% higher than that in the UPCB. Mineralization capability of UPCB was even worse, due to less adsorbable intermediates and cell lysis induced soluble microbial products release. The lower phenol degradation in the UPCB was due to the serious detachment of the biofilms, and then the microbes responsible for phenol degradation were insufficient due to disinfection by UV irradiation. In contrast, microbial communities in the carriers were well protected under visible light irradiation and extracellular polymeric substances secretion was enhanced. Thus, we found that the photocatalytic reaction and biodegradation were intimately coupled in the VPCB, resulting in 64.0% removal of dissolved organic carbon. Therefore, we found visible light has some advantages over UV light in the ICPB technology.

Improving oxygen dissolution and distribution in a bioreactor with enhanced simultaneous COD and nitrogen removal by simply introducing micro-pressure and swirl.

Increasingly, environmental regulations are demanding more exacting chemical oxygen demand (COD) and nitrogen removal from wastewater, which come at a high economic cost. A very simple novel bioreactor, the micro-pressure swirl reactor (MPSR), can improve the dissolution and distribution of oxygen by the introduced micro-pressure swirl. Comparison with a conventional sequencing batch reactor (SBR) over 76 days of operation showed that this method can enhance simultaneous COD and nitrogen removal. By installing an aeration diffuser on one side of the two-dimensional MPSR, a swirl formed in the bioreactor that extended the retention time of the air bubbles. This unique flow regime, combined with the micro-pressure caused by the elevated water surface at the bubble outflow point, resulted in a higher level of dissolved oxygen (DO) in the MPSR. Aerobic and anaerobic zones that created appropriate conditions for simultaneous COD and nitrogen removal also formed in the MPSR. As the organic loading rate increased from 0.29 to 1.68 g COD/(L · day) over the test period, the COD removal efficiencies of the MPSR were generally 10-20 % greater than those of the SBR. In particular, the total nitrogen (TN) removal efficiencies of the MPSR and SBR were 40-50 and 20-35 %, respectively, whereas the TN concentrations in the MPSR effluent were always around 10 mg/L lower than those of the SBR. Further, because of the unique DO distribution, the bacterial species in the MPSR were more diverse and contributed to enhanced TN removal.

Study of phosphate removal from aqueous solution by zinc oxide.

Zinc oxide (ZnO) was synthesized and used to investigate the mechanism of phosphate removal from aqueous solution. ZnO particles were characterized by X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy before and after adsorption. Batch experiments were carried out to investigate the kinetics, isotherms, effects of initial pH and co-existing anions. The adsorption process was rapid and equilibrium was almost reached within 150 min. The adsorption kinetics were described well by a pseudo-second-order equation, and the maximum phosphate adsorption capacity was 163.4 mg/g at 298 K and pH ∼6.2±0.1. Thermodynamic analysis indicated the phosphate adsorption onto ZnO was endothermic and spontaneous. The point of zero charge of ZnO was around 8.4 according to the pH-drift method. Phosphate adsorption capacity reduced with the increasing initial solution pH values. The ligand exchange and Lewis acid-base interaction dominated the adsorption process in the lower and the higher pH range, respectively. Nitrate, sulfate and chloride ions had a negligible effect on phosphate removal, while carbonate displayed significant inhibition behavior.

Effects of surfactants on graphene oxide nanoparticles transport in saturated porous media.

Transport behaviors of graphene oxide nanoparticles (GONPs) in saturated porous media were examined as a function of the presence and concentration of anionic surfactant (SDBS) and non-ionic surfactant (Triton X-100) under different ionic strength (IS). The results showed that the GONPs were retained obviously in the sand columns at both IS of 50 and 200mmol/L, and they were more mobile at lower IS. The presence and concentration of surfactants could enhance the GONP transport, particularly as observed at higher IS. It was interesting to see that the GONP transport was surfactant type dependent, and SDBS was more effective to facilitate GONP transport than Triton X-100 in our experimental conditions. The advection-dispersion-retention numerical modeling followed this trend and depicted the difference quantitatively. Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction calculations also were performed to interpret these effects, indicating that secondary minimum deposition was critical in this study.

Optimal poly (3-hydroxybutyrate/3-hydroxyvalerate) biosynthesis by fermentation liquid from primary and waste activated sludge.

In this paper the production of poly (3-hydroxybutyrate/3-hydroxyvalerate) (PHBV) with activated sludge was investigated by using the fermentation liquid from primary sludge (PS) and waste activated sludge (WAS) as carbon source. First, the suitable concentration and ratio of acetic to propionic (acetic/propionic) for PHBV synthesis with desired hydroxyvalerate (HV) fraction was determined. Then, the conditions for producing fermentation liquid with the required acetic/propionic from the PS/WAS mixture were optimized. Finally, this optimized fermentation liquid was used as the carbon source for PHBV synthesis by the aerobic feeding and discharge process. The PHBV content in the sludge reached 65.5%, with 47.8% (mol-C based) of HV unit content, and the corresponding polyhydroxyalkanoates yield per litre of acclimated sludge was 1.44 g/L. This was the first optimal PHBV biosynthesis reported by using activated sludge as the microbe and sludge fermentation liquid as the carbon source. Polymerase chain reaction-based 454 pyrosequencing analysis revealed that Thauera strains were the predominant species in the PHBV biosynthesis system.

Understanding microplastic presence in different wastewater treatment processes: Removal efficiency and source identification.

Municipal effluents discharged from wastewater treatment plants (WWTPs) are a considerable source of microplastics in the environment. The dynamic profiles of microplastics in treatment units in WWTPs with different treatment processes remain unclear. This study quantitatively analyzed microplastics in wastewater samples collected from different treatment units in two tertiary treatment plants with distinct processes. The influents contained an average of 15.5 ± 3.5 particles/L and 38.5 ± 2.5 particles/L in the two WWTPs with in the oxidation ditch process and the integrated fixed-film activated sludge process, respectively. Interestingly, microplastic concentrations in the influent were more influenced by the population density in the served area than sewage volume or served population equivalent. Throughout the treatment process, concentrations were reduced to 1.5 ± 0.5 particles/L and 1.0 ± 1.0 particles/L in the final effluents, representing an overall decrease of 90% and 97%, in WWTPs with the oxidation ditch process and integrated fixed-film activated sludge process, respectively. A significant proportion of the microplastics were removed during the primary treatment stage in both WWTPs, with better performance for foam, film, line-shaped and large-sized microplastics. Most microplastics were accumulated in activated sludge, indicating its key role as the primary sink in WWTPs. The multiple correspondence analysis identified laundry washing and daily necessities such as packaging and containers as the major contributors to microplastics in WWTPs. The study proposed recommendations for upgrading WWTPs, modifying designs, and implementing strategies to reduce microplastic sources, aiming to minimize the release of microplastics into the environment. These findings can shed lights on the sources of microplastics in WWTPs, and advance our understanding of the mechanisms for more effective microplastic removals in wastewater treatment technologies in future applications.

More resilient polyester membranes for high-performance reverse osmosis desalination.

Thin-film composite reverse osmosis membranes have remained the gold standard technology for desalination and water purification for nearly half a century. Polyamide films offer excellent water permeability and salt rejection but also suffer from poor chlorine resistance, high fouling propensity, and low boron rejection. We addressed these issues by molecularly designing a polyester thin-film composite reverse osmosis membrane using co-solvent-assisted interfacial polymerization to react 3,5-dihydroxy-4-methylbenzoic acid with trimesoyl chloride. This polyester membrane exhibits substantial water permeability, high rejection for sodium chloride and boron, and complete resistance toward chlorine. The ultrasmooth, low-energy surface of the membrane also prevents fouling and mineral scaling compared with polyamide membranes. These membranes could increasingly challenge polyamide membranes by further optimizing water-salt selectivity, offering a path to considerably reducing pretreatment steps in desalination.

Modulating electron density enable efficient cascade conversion from peroxymonosulfate to superoxide radical driven by electron-rich/poor dual sites.

The superoxide radical (•O2-)-mediated peroxymonosulfate (PMS)-based photo-Fenton-like reaction enables highly selective water decontamination. Nevertheless, the targeted construction of •O2--mediated photo-Fenton-like system has been challenging. Herein, we developed an electron-rich/-poor dual sites driven •O2--mediated cascade photo-Fenton-like system by modulating electron density. Experimental and theoretical results demonstrated that PMS was preferentially adsorbed on electron-poor Co site. This adsorption promoted O-O bond cleavage of PMS to generate hydrogen peroxide (H2O2), which then migrated to electron-rich O site to extract eg electrons for O-H bond cleavage, rather than competing with PMS for Co site. The developed versatile cascade reaction system could selectively eliminate contaminants with low n-octanol/water partition constants (KOW) and dissociation constants (pKa) and remarkably resist inorganics (Cl-, H2PO4- and NO3-), humic acid (HA) and even real water matrices (tap water and secondary effluent). This finding provided a novel and plausible strategy to accurately and efficiently generate •O2- for the selective water decontamination.