Comparable Removal Efficiencies Research Articles

Construction of CuMoO4/MnO2/tourmaline composite for efficient organic wastewater decontamination via photo-Fenton-like processes

A CuMoO4/MnO2/tourmaline (CMT) heterogeneous photocatalyst was successfully constructed by hydrothermal method followed by calcination and applied to activate peroxymonosulfate (PMS) for organic contaminant degradation over a wide pH range under visible light illumination. The CMT catalyst exhibited impressive degradation efficiencies of tetracycline hydrochloride (TC, 93.48%), safranine T (SaT, 100%), acridine orange (AO, 99.46%), methyl orange (MO, 97.47%), neutral red (NR, 94.10%), trypan blue (TB, 93.67%), methylene blue (MB, 90.36%) and rhodamine B (RhB, 89.85%) within 50 min. The influence of related parameters including catalyst dosage, PMS concentration, initial pH value, TC concentration, coexisting ions, humic acid (HA) and different water matrices on TC degradation were systematically investigated. According to quenching experiments and electron paramagnetic resonance (EPR) tests, e−, SO4•−, •OH, •O2− and 1O2 all contributed to TC degradation, and •O2− played a predominant role in the photo-Fenton-like process. The reusability of CMT was evaluated by consecutive experiments, and comparable removal efficiencies could be maintained after five cycles. The degradation pathways of TC were deduced and the toxicity of degradation intermediates based on HPLC−MS detection was estimated by Toxicity Estimation Software (T.E.S.T.). Moreover, the catalytic degradation mechanisms of TC in CMT/PMS/Vis system were further proposed and the role of tourmaline was illustrated. This work opens an avenue for the construction of heterogeneous catalysts based on natural minerals in PMS/Vis coupling system for wastewater decontamination.

Harnessing water fleas for water reclamation: A nature-based tertiary wastewater treatment technology

Urbanisation, population growth, and climate change have put unprecedented pressure on water resources, leading to a global water crisis and the need for water reuse. However, water reuse is unsafe unless persistent chemical pollutants are removed from reclaimed water. State-of-the-art technologies for the reduction of persistent chemical pollutants in wastewater typically impose high operational and energy costs and potentially generate toxic by-products (e.g., bromate from ozonation). Nature-base solutions are preferred to these technologies for their lower environmental impact. However, so far, bio-based tertiary wastewater treatments have been inefficient for industrial-scale applications. Moreover, they often demand significant financial investment and large infrastructure, undermining sustainability objectives. Here, we present a scalable, low-cost, low-carbon, and retrofittable nature-inspired solution to remove persistent chemical pollutants (pharmaceutical, pesticides and industrial chemicals). We showed Daphnia's removal efficiency of individual chemicals and chemicals from wastewater at laboratory scale ranging between 50 % for PFOS and 90 % for diclofenac. We validated the removal efficiency of diclofenac at prototype scale, showing sustained performance over four weeks in outdoor seminatural conditions. A techno-commercial analysis on the Daphnia-based technology suggested several technical, commercial and sustainability advantages over established and emerging treatments at comparable removal efficiency, benchmarked on available data on individual chemicals. Further testing of the technology is underway in open flow environments holding real wastewater. The technology has the potential to improve the quality of wastewater effluent, meeting requirements to produce water appropriate for reuse in irrigation, industrial application, and household use. By preventing persistent chemicals from entering waterways, this technology has the potential to maximise the shift to clean growth, enabling water reuse, reducing resource depletion and preventing environmental pollution.

Elimination of sulfadiazine and its metabolite from hydrolyzed urine by biochar activated periodate process: Lower environmental risk compared with CoFe2O4/peroxymonosulfate process

Source-separation and treatment of urine are recognized as promising strategies to recover nutrients, as well as reduce the stress of terminal wastewater treatment plants. As a ubiquitous constituent of urine, NH4+ has been demonstrated to induce the generation of nitro-byproducts in sulfate radical (SO4•−) dominated oxidation processes. In this work, wheat straw derived biochar (BCX, X represents the pyrolysis temperature) was prepared and adopted to eliminate sulfadiazine (SDZ) and its main human metabolite N4-acetyl-sulfadiazine (NSDZ) from hydrolyzed urine by coupling with periodate (PI). Specifically, BC800/PI process achieved excellent SDZ (0.190 h−1) abatement, which was more efficient than NSDZ. HCO3− and NH4+ significantly inhibited the removal processes whilst Cl− showed neglected effect. Both in situ and ex situ analysis excluded the dominant role of •OH, 1O2, O2•– and/or •IO3. Instead, electron-transfer regime driven by the high potential BC800-PI* complexes played a significant role. Interestingly, BC800/PI and CoFe2O4/peroxymonosulfate (PMS) (a typical SO4•−-dominated oxidation process) exhibited comparable removal efficiencies towards SDZ. Four nitro-byproducts were identified in CoFe2O4/PMS process but negligible in BC800/PI process during SDZ treatment, revealing the merit of BC800/PI process. Eventually, the toxicity prediction and bactericidal experiments further implied that BC800/PI process was eco-friendly. This study proposed a heterogeneous BC800/PI process for the treatment of source-separated urine and comprehensively demonstrated the advantages of its low costs and environmental risk.

Hydrolyzed polyacrylonitrile UF-membrane for surface and TAP water treatment: Influence on DBPs formation and removal

The integration of pre-treatment methods with low pressure-driven ultrafiltration (UF) has been found effective for reducing the formation of disinfection by-products (DBPs) in drinking water. In this study, a low dose peroxone (H2O2/O3) assisted alkaline hydrolyzed polyacrylonitrile (HPAN) UF-membrane system was explored, to determine its performance efficiency against two dissolved organic matter (DOM) sources and TAP water, specifically focusing the formation and removal of regulated DBPs. Increased hydrophilicity, enhanced incorporation of carboxyl groups, and decreased surface porosity were observed for the PAN membrane as a function of increased hydrolysis time. Filtration experiments involving humic acid (HA) and samples of real DOM sources displayed a high flux recovery (>90%) with the HPAN membrane. The initial flux for the optimized HPAN was found to be twice than that of the NF-3 membrane, irrespective of the DOM source. However, a relatively comparable removal efficiency was observed for both HPAN and NF-3 membranes in terms of organic matter and DBPs formation potential. Additionally, the H2O2/O3-HPAN system significantly reduced the aromatic and fluorescent content of the DOM by upto 70–80%, as represented by the DOC, UV254 and parallel factor analysis (PARAFAC) components. The fluorescence ratio C1/C2 showed a relatively greater reduction for soil-derived organic matter (SOM) as compared to the Olympic Lake (OL) water. Post-chlorination was found highly effective for the degradation of the humic-like DOM component (C1) than that of the fulvic and protein-like components. Moreover, the integration of H2O2/O3 with HPAN was able to remove 80% of the THMs and HAAs formation for both OL and SOM samples, together with a comparable reduction in DBP cytotoxicity. Interestingly, the HPAN membrane by reducing the TAP water DBPs upto 50%, fulfills the criteria of USEPA maximum contaminant level for drinking water.

Comparative study of adsorption of cationic dyes on novel surface functionalized mesoporous titanate‐based materials

AbstractOrganic dyes have caused many negative effects on the aqueous environment and human health. Therefore, removal of organic dyes from water is a great challenge of seeking an effective methodology. Titanate‐based materials have been received much attraction and recognized as effective adsorbents for wastewater treatment. This study represented the feasibility of novel carbonaceous mesoporous titanate‐based materials (Na2Ti3O7/Na3Ti6O13) successfully synthesized via a EDTA‐Na2 assisted method to be used as adsorbents for removal of cationic dyes (methylene blue‐MB, and crystal violet‐CV). The samples synthesized with different molar ratios of EDTA‐Na2 (0.5, 1.0, 1.5 vs TiO2) were characterized by different analysis methods (SEM‐EDX, FT‐IR, XRD, BET and UV‐Vis). They were also tested for the treatment of both two dyes. Results showed that the sample with 1.0 EDTA‐Na2:1.0 TiO2 (MT1.0:1.0) had the highest and comparable removal efficiency for MB and CV among the as‐synthesized samples. The adsorption of both two dyes on MT1.0:1.0 followed the Langmuir isotherm with maximum adsorption capacities of 27.5 and 3.9 mg.g‐1 for MB and CV, respectively. It can also be found that the pseudo‐second‐order model showed the best fit with R2 values of 0.99 and 0.98 for MB and CV, respectively.

Performance and mechanism of constructed wetland-microbial fuel cell systems in treating mariculture wastewater contaminated with antibiotics

Mariculture wastewater has raised great concerns owing to its potential impact on the sustainability of coastal environments and aquaculture practices. In this study, constructed wetlands coupled with microbial fuel cells (CW-MFCs) were constructed to evaluate their ability to treat mariculture wastewater that has been contaminated with antibiotic sulfadiazine (SDZ). The results showed that both open- and closed-circuit CW-MFCs (R1 and R2) had comparable removal efficiencies for NH4+-N, total inorganic nitrogen (TIN), chemical oxygen demand (COD), and total phosphorus (TP). Compared with R3, which had no SDZ, R2 was less efficient at removing NH4+-N and TP, and also presented inhibited electricity generation. R2 in closed-circuit mode was more efficient at removing SDZ than R1 in open-circuit mode. However, R2 also had a higher relative abundance of antibiotic resistance genes (ARGs) in the anode region and cathode effluent than R1, indicating that the closed-circuit CW-MFC system was inferior to the open-circuit system in controlling ARGs. High-throughput sequencing analysis suggested that the presence of SDZ and being in closed-circuit mode both increased the diversity of the microbial community, which in turn led to changes in the removal efficiency of SDZ and the system’s ability to generate electricity. The potential hosts of the three ARGs at the phylum level were mainly from Proteobacteria, Desulfobacterota, Patescibacteria, Firmicutes, Actinobacteriota, and Spirochaetota. Notably, some genera related to sulfur transformation in Desulfobacterota showed strong positive correlations with ARGs. This study is beneficial to expand the application of CW-MFCs in the treatment of antibiotic-contaminated mariculture wastewater.

Removal of organic micropollutants from municipal wastewater by powdered activated carbon - activated sludge treatment

In Powdered Activated Carbon (PAC)-Activated Sludge (AS) Treatment, PAC is directly dosed into the AS tank. In this study, batch and pilot plant experiments were carried out to investigate the efficacy of PAC-AS treatment concerning the removal of organic micropollutants (OMPs). Batch and pilot plant experiments showed comparable removal efficiency of nine OMPs: a mean removal of 80 % could be achieved at a specific PAC dose of 2.5 mg PAC/mg DOC; during a PAC cut-off experiment, the removal performance leveled off in the first 6 h without PAC dosage. A further investigation involving an intermittent dosage of PAC demonstrated that OMPs were removed stably when PAC was dosed every 6 h, which implies the possibility of reduced investment and maintenance costs of a dosing unit.DOC was removed by 18 ± 4 % when the PAC doses ranged from 1.9 to 2.3 mg PAC/mg DOC in this study. A more detailed characterization of the organic matter was performed by means of size exclusion chromatography coupled with organic carbon detection (SEC-OCD). The high molecular weight fraction (F1) and hydrophobic organic compounds (DOCh) were most adsorbed by PAC, revealed by batch and pilot plant experiments. It indicates a higher competition potential of these two fractions against OMP adsorption compared to other DOC fractions in the PAC-AS system.

Facile synthesis of copper oxide nanoparticles and their applications in the photocatalytic degradation of acyclovir

Copper oxide nanoparticles were synthesized by a simple sol-gel route using copper (II) acetate monohydrate as a precursor at varying temperatures (300 °C, CuO(300); 350 °C, CuO(350) and 400 °C, CuO(400)), and were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV–visible absorption spectroscopy. While the lowest temperature of calcination (300 °C) yielded mixed phases of CuO and Cu2O, the higher temperature (350 °C and 400 °C) gave pure monoclinic crystal phase of CuO. The microscopic analysis revealed that both CuO samples exhibited spherical shape with the average particle size of 47.15 nm (350 ᵒC) and 47.67 nm (400 ᵒC). The crystallite size estimated from the XRD pattern showed average crystalline sizes of 32.16 and 32.45 nm at 350 and 400 °C respectively. Photocatalytic degradation of acyclovir (ACV) was conducted using the nanoparticles and the effect of process variables such as catalyst dosage and solution pH were evaluated in order to establish the efficiency of the CuO nanoparticles in the photocatalytic process. The photo-enhanced degradation of ACV using both CuO nanoparticles demonstrated high and comparable removal efficiency of greater than 81%, within 120 min irradiation time. The results also showed that the performance of both CuO is dependent. The efficient performance achieved with both CuO photocatalysts, without further modification, suggests that the synthesized CuO nanoparticles could be a potential photocatalyst to remove ACV-laden water.

Oxidative decomposition with PEG-MnO2 catalyst for removal of formaldehyde: Chemical aspects on HCHO oxidation mechanism

Formaldehyde (HCHO) is a representative indoor pollutant that can adversely affect human health, and research on HCHO removal at room temperature is actively needed. In this study, a carbon-based material, Polyethylene glycol #20000(PEG #20000), is used to prepare PEG-MnO2 by doping on MnO2. Glucose-doped MnO2 (G-MnO2) and birnessite-doped MnO2 (δ-MnO2) are utilized to compare removal efficiencies with PEG-MnO2. The efficiency of PEG-MnO2 is measured to be 96.8 % under the conditions of 60 % relative humidity and GHSV of 240 L⋅gcat-1⋅h−1. In addition, PEG-MnO2 catalysts demonstrated longer stability by maintaining a constant efficiency for 720 min. The superior performance of PEG-MnO2 is due to the formation of oxygen vacancies after PEG-doping which promote the oxidation of HCHO. Therefore, PEG-MnO2 is expected to attract attention as a catalyst for HCHO removal at room temperature because it is easy to synthesize and has superb catalytic performance.

Early breakthrough of short‐chain perfluoroalkyl substances in adsorptive media treatment

AbstractActivated carbon (AC) adsorption continues to be the default technology to remove low levels of per‐ and polyfluoroalkyl substances (PFAS) from water, despite varying reports of the relatively early breakthrough of short‐chain PFAS and high operating costs. Ion‐exchange processes using regenerable and single‐use media have been emerging as practical alternatives which may provide improved treatment and system performance. However, long‐term performance with respect to the more difficult to remove short‐chain PFAS such as perfluorobutanoic acid and perfluorobutanesulfonic acid is less often reported. Treatability testing on PFAS‐impacted groundwater using batch‐equilibration reactors and column flushing apparatus experiments was implemented to compare removal efficiency, breakthrough, and longevity of various media, specifically for shorter chain PFAS. Adsorbents tested included surface‐modified natural media, synthetic resin, and AC. Results indicated that both surface modified natural media and AC achieved >99 percent removal of all detected PFAS after approximately 10,300‐bed volumes (16 weeks) of column flushing, and outperformed the selected resin under site‐specific conditions. In addition, unconventional breakthrough patterns (i.e., the breakthrough of longer chain PFAS before shorter chain PFAS) were observed for some PFAS including perfluoropentanoic acid, perfluorohexanesulfonic acid, and perfluorooctanesulfonic acid. The results of this study suggested that, while the generally accepted breakthrough patterns for PFAS can be reasonably anticipated, column flushing studies were preferred over batch sorption tests to reveal site‐specific or media‐specific breakthrough patterns that can impact overall performance.

Tar mitigation using insitu heat generation chemicals (part I): A comparative study

Tar is an extra-heavy oil with ultra-high viscosity. Accumulation of tar in a reservoir ultimately results in production decline. This study represents the first part of the series of investigation, which aim at developing an insitu heat generation scheme (through thermochemical reaction) for tar mitigation to improve oil production from tarmat-impacted reservoir. Comparative studies have been conducted through both coreflooding experiments and field scale numerical simulation for tar removal using injection of thermochemical fluids (TCF) at 90 °C and other fluids, including water (23 °C), hot water (90 °C), oil soluble organic solvent sludge (90 °C) and steam (210 °C). The results from coreflooding experiments revealed that TCF injection has comparable removal efficiency in terms of recovery factor (RF = 93%), with that of steam injection (RF = 94%). In comparison, the RF from water, hot water, and injection of an oil-soluble solvent sludge are 21, 53, and 85%, respectively. From the field scale simulation, the results affirmed greater efficiency of TCF injection over steam injection with higher tar recovery rate, recovery factor (RF), and Oil: Steam ratio (OSR). In addition, the simulation results revealed that cyclic injection of TCF outperformed continuous injection operation.

Sub-micro photocatalytic TiO2 particles for a water depollution: Comparable removal efficiency to commercial P25 and easy separation via a simple sedimentation

The sub-micrometer sized TiO2 particles (100–200 nm) were synthesized by a sol-gel and subsequent thermal annealing. The particle size, surface area, pore structure, and crystallinity were varied upon the annealing temperatures (450, 550, 650 °C). The photocatalytic activities of three TiO2 particles annealed at various temperatures (450-, 550-, and 650-TiO2) were examined by performing photocatalytic depollution of three organic model pollutants (methylene blue, methyl orange, and phenol) from aqueous solutions under the UV light irradiation. Among three samples, 550-TiO2 (~200 nm) exhibited the highest photocatalytic activity towards the removals of all three model pollutants. Photocatalytic activity of the 550-TiO2 was compared with a commercial TiO2 (P25, Evonik) at various conditions of loading amounts of particles dispersed in MB solution. Light scattering by dispersed particles at high sample loading conditions was less pronounced in the case of 550-TiO2. Therefore, the sub-micro 550-TiO2 particles can exhibit comparable activity to P25 at high sample loading conditions (2–4 g/L). In addition, the bigger size of 550-TiO2 made it possible to separate them via a simple sedimentation process, showing a potential of sub-micro TiO2 particles as an efficient photocatalysts for water depollution.

Adsorption and Release Characteristics of Purified and Non-Purified Clinoptilolite Tuffs towards Health-Relevant Heavy Metals

The occurrence of health-relevant contaminants in water has become a severe global problem. For treating heavy-metal-polluted water, the use of zeolite materials has been extended over the last decades, due to their excellent features of high ion exchange capacity and absorbency. The aim of this study was to assess the effect of heavy metal uptake of one purified (PCT) and two non-purified clinoptilolite tuffs (NPCT1 and NPCT2) in aqueous solutions on monovalent ions Ni+, Cd+, Cs+, Ba+, Tl+, and Pb+. Experiments were furthermore carried out in artificial gastric and intestinal fluids to mimic human digestion and compare removal efficiencies of the adsorbent materials as well as release characteristics in synthetic gastric (SGF) and intestinal fluids (SIF). Batch experiments show low sorption capacities for Ni+ and Cd+ for all studied materials; highest affinities were found for Ba+ (99–100%), Pb+ (98–100%), Cs+ (97–98%), and Tl+ (96%), depending on the experimental setup for the PCT. For the adsorption experiments with SGF, highest adsorption was observed for the PCT for Pb+, with an uptake of 99% of the lead content. During artificial digestion, it was proven that the PCT did not release Ba+ cations into solution, whereas 13,574 ng·g−1 and 4839 ng·g−1 of Ba+ were measured in the solutions with NPCT1 and NPCT2, respectively. It was demonstrated that the purified clinoptilolite tuff is most effective in remediating heavy-metal-polluted water, particularly during artificial digestion (99% of Pb+, 95% of Tl+, 93% of Ba+). In addition, it was shown that the released amount of bound heavy metal ions (e.g., barium) from the non-purified clinoptilolite tuffs into the intestinal fluids was significantly higher compared to the purified product.

Arsenic removal characteristics of natural Mn-Fe binary coating on waste filter sand from a water treatment facility.

In this study, the arsenic (As) removal characteristics of a Mn-Fe binary coating formed on waste sand filter of an acid mine drainage treatment facility are investigated. Owing to the Mn-Fe binary coating forming on the surfaces of the sand grains, its potential for arsenic removal, particularly As(III), was evaluated and characterized through batch experiments and x-ray absorption spectroscopy. Sorption isotherms reveal that the Mn-Fe binary coating exhibits comparable removal efficiencies for As(III) and As(V) under low initial As concentrations. However, at higher initial As(III) and As(V) concentrations, the As(III) removal efficiency increases because of newly formed active adsorption sites from reductive dissolution of Mn. The oxidation of the As(III) and reduction of the Mn oxide phases are verified through As K-edge and Mn K-edge X-ray absorption near edge fine structure analysis. The outstanding As(III) removal efficiency of the Mn-Fe binary coating suggests synergy of Fe- and Mn-oxides, highlighting a potential application for this coating system. The natural formation of binary coating through acid mine drainage treatment reported in this study indicates that similar coating can form naturally in other environments, thus, providing plausible natural attenuation processes for arsenic immobilization.

Facile pyrrole oxidative polymerization with ionic liquid to modify ceramic membrane for sustainable fouling control

Ceramic membrane bioreactor (CMBR) is an attractive alternative for wastewater treatment, although still subjects to fouling problem. This study facilely modified CM by oxidative polymerization of pyrrole with ionic liquid, to greatly enhance its conductivity and hydrophilic, and to sustainably mitigate fouling in an electric CMBR. Highly conductive ceramic membrane, BVIMBF4-CM, was facile obtained involving an ionic liquid 1-vinyl-3-butylimidazolium tetrafluoroborate (BVIMBF4) on the base CM (Base-CM). After simple modification, the electrical resistance of CM was reduced significantly from 1017 Ω/sq to 349 Ω/sq, while its water contact angle decreased from 44.0° to 30.5°. With the assistant of minute electric field, BVIMBF4-CM exhibited a high rejection efficiency of over 85% Cu2+, 65% Ni2+ and 93% bovine serum albumin (BSA). The interaction energy analysis verified BVIMBF4-CM itself prevent BSA from the membrane surface by the positive total interfacial energy. Meanwhile, the electrophoretic force provided by electric field enhanced the removal efficiency and antifouling capability of the BVIMBF4-CM. By using this modified CM to form an E-CMBR, a comparable removal efficiency as the CMBR could be stably obtained, which especially demonstrated significantly anti-fouling performance, as fouling rate decreased by 31.4–43.5%, and the total membrane resistance was only 60.8% of the Base-CM, under a minute electric field of 0.8 V/m. Enhanced hydrophilicity and conductivity of the BVIMBF4-CM take major responsible for this stable fouling alleviation in the E-CMBR. The new and facile method for CM modification proposed herein can serve as a reliable effort towards the application of antifouling E-CMBR system in wastewater treatment.

Integrated Leaching and Thermochemical Technologies for Producing High-Value Products from Rice Husk: Leaching of Rice Husk with the Aqueous Phases of Bioliquids

It remains challenging to develop a techno-economically feasible method to remove alkali and alkaline earth metal species (AAEMs) from rice husk (RH), which is a widely available bioresource across the world. In this study, the AAEMs leaching effect of aqueous phases of both bio-crude prepared by hydrothermal liquefaction (AP-HT) and bio-oil prepared by pyrolysis (AP-Pyro) of RH were systematically investigated. The results indicated that although the acidity of AP-HT and AP-Pyro are much lower than that of HCl, they performed a comparable removal efficiency on AAEMs (Na: 56.2%, K: 96.7%, Mg: 91.0%, Ca: 46.1% for AP-HT, while Na: 58.9%, K: 96.9%, Mg: 94.0%, Ca: 86.3% for AP-Pyro) with HCl. The presence of phenolics in bio-oil could facilitate the penetration of water and organic acids into the inner area of RH cells, thus enhancing the AAEMs removal via chelate reactions. The thermal stability of leached RH during thermochemical conversions was studied via TG and Py-GC-MS. The results showed that the heat conduction efficiency in leached RH was enhanced with a high pyrolysis rate, resulting in a narrow carbon chain distribution (C5–C10) of derived chemical compounds.

Soluble chemical oxygen demand removal from bypass wastewater using iron electrocoagulation

In-plant wastewater treatment strategies to handle bypass wastewater exceeding design capacity are insufficiently investigated in the scientific literature notwithstanding their importance in ensuring sustainable wastewater management. In this study, the effectiveness of iron electrocoagulation was investigated, for the first time, to enhance primary treatment capability in removing soluble chemical oxygen demand (sCOD) from bypass wastewater. In addition, the appropriate assumptions and experimental protocols for the application of adsorption isotherm models, widely used to describe the electrocoagulation process, were discussed in light of experimental results. Under neutral pH conditions, the bypass wastewater treatment was performed to test the effects of three preselected variables (electrolysis duration, current density, and temperature) on sCOD removal. Using a 15 mA/cm2 current density, an average 52% sCOD removal efficiency was achieved after 15 min at 23 °C while approximately 40 min were needed to attain comparable removal efficiency at 8 °C. sCOD removals of 74% and 87% were achieved after 40 min treatment using a 22 mA/cm2 current density at 8 °C and 23 °C, respectively. Experimental results and theory show that adsorption equilibrium was not reached in the electrocoagulation cell; consequently, variable-order-kinetic (VOK) models derived from Langmuir and Langmuir-Freundlich adsorption expressions were adapted to describe the process. These models were modified to account for the de facto estimation of ferric hydroxide (adsorbent) mass that accounts for the conversion of ferrous ion to particulate end products. The Langmuir-based VOK model was found to better describe sCOD removal under all the operating conditions tested and showed the sCOD removal mechanism to be consistent with chemisorption. This research shows the promising ability of iron electrocoagulation to achieve superior removal of sCOD as compared to established and emerging standalone bypass wastewater treatment technologies.

Effectiveness of biosurfactant for the removal of trihalomethanes by biotrickling filter.

In this study, the biodegradation of a mixture of two trihalomethane (THM) compounds, chloroform (CF) and dichlorobromomethane (DCBM), was evaluated using two laboratory-scale biotrickling filters (BTFs). The two BTFs, hereby designated as "BTF-A" and "BTF-B," were run parallel and used ethanol as co-metabolite at different loading rates (LRs), and a lipopeptide-type biosurfactant that was generated by the gram-positive bacteria, Surfactin, respectively. The results using BTF-A showed that adding ethanol at a higher rate of 4.59 g/(m3 h) resulted in removal efficiencies of 85% and 87% for CF and DCBM, respectively. Conversely, for the same LR, the use of Surfactin without ethanol (BTF-B) showed comparable removal efficiencies of 85% and 80% for CF and DCBM, respectively. The maximum rate constant for CF and DCBM for the BTF-A was 0.00203 s-1 and 0.0022 s-1, respectively. For the same THMs LR, similar reaction rate constants resulted for the BTF-B. Further studies were conducted to investigate and understand the microbial diversity within both BTFs. The result indicated that for BTF with co-metabolite, Fusarium sp. was the most dominant fungi over 98% followed by F. Solani with less than 2%. F. oxysporum and Fusarium sp. were instead the dominant fungi for the BTF with Surfactin. Before introducing the Surfactin into the BTF, the batch experiment was conducted to evaluate the effectiveness of synthetic surfactant as compared to a biosurfactant (Surfactin). In this regard, vials with Surfactin showed better performance than vials with Tomadol 25-7 (synthetic surfactant).

Electro-remediation of tailings from a multi-metal sulphide mine: comparing removal efficiencies of Pb, Zn, Cu and Cd

ABSTRACTSulphidic mine tailings characterised by high concentrations of heavy metals (Pb 3532 ± 97 mg/kg, Zn 8450 ± 154 mg/kg, Cu 239 ± 18 mg/kg and Cd 14.1 ± 0.3 mg/kg) and abundant carbonate (17%) were subjected to eight lab-scale electrodialytic remediation (EDR) experiments to investigate the influence of current density, treatment time and particle size on removal efficiency. Pb and Cu removal improved when increasing current density, while Zn and Cd removal did not. In contrast Zn and Cd removal improved by grinding the tailings, while Pb and Cu removal did not. At the highest current density (1.2 mA/cm2), 94%, 75%, 71% and 67% removal of Pb, Zn, Cu and Cd could be achieved, respectively, on grinded tailings in 28 days. Sequential chemical extraction made before and after EDR revealed larger oxidisable fractions of Zn, Cu and Cd, representing large fractions of sulphides, which was likely to be the main barrier to be removed as efficiently as Pb. This was in accordance with acid/base extraction tests in which Pb showed high solubility at both high and low pH (up to 65% and 86% of extraction, respectively), while considerable extraction of Zn (55%) happened only at low pH; and very limited extraction (<20%) of Cu and Cd occurred at any pH.

Electrocoagulation of boron by electrochemically co-precipitated spinel ferrites

Magnetically separable spinel ferrites were created in an electrocoagulation (EC) process for removing boron from aqueous solution. Coprecipitates of NiFe2O4, CoFe2O4 and CuFe2O4 were obtained using sacrificial iron anodes (EC-Fe) in an electrolyte that contained transition metal salts (Ni, Co, Cu). The use of nickel chloride (NiCl2) as the supporting electrolyte yielded the highest boron removal since the maximum adsorption capacity of the resulting sludge was 28.9 mg-B/g. An EC that used iron and nickel as anodes (EC-Fe/Ni) in NaCl electrolyte was then employed to form nickel ferrite by electrochemical dissolution of ferrous (Fe(II)) and nickel (Ni(II)) ions, providing comparable removal efficiency but minimizing the residual level of Ni(II) in the treated water. The saturation magnetization of the precipitate that was produced in the EC-Fe/Ni system was 50.3 emu/g which exceeded that in the EC-Fe system with nickel chloride – 21.8 emu/g, indicating its outstanding magnetic separability. EC-Fe/Ni was optimized to remove 95% of boron from solution in 60 min with an initial boron concentration of 10 ppm at pH 8 and a current density of 3.75 mA/cm2.