Affecting Removal Efficiency Research Articles

Reaction Mechanism of Oxytetracycline Degradation by Electrogenerated Reactive Chlorine: The Influence of Current Density and pH.

A binary dimensionally stable anode Ti/TiO2-RuO2 electrode was used to abate the antibiotic oxytetracycline (OTC) (C22H24N2O9) in chloride water. The anode was prepared using the Pechini method and subsequently characterized by X-ray diffraction, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), and cyclic voltammetry (CV). The optimum values of the operational parameters affecting removal efficiency were determined using a 2 × 3 factorial design by screening j (6.0, 10, and 20 A m-2) and pH (3, 6.5, and 10). The textural analysis revealed the formation of active oxides (RuO2 and TiO2 coating rutile-type P42/mnm, space group 136), with a cracked surface and good dispersion of metal components. A contour graph verified that the most suitable condition for contaminant degradation was 20 A m-2 at a circumneutral pH of 6.5, resulting in approximately 97% degradation after 20 min of electrolysis according to pseudo-first-order reaction kinetics and the loss of the antibiotic activity of OTC. In addition, the results of oxidant formation and CV indicate that the best electrochemical activation of the anode to form Cl2-active mainly depended on pH. Liquid chromatography-mass spectrometry (LC-MS) and density functional theory were employed to propose a reaction pathway for OTC degradation. Three byproducts with m/z 426, 256, and 226 were identified corresponding to the removal of amide and amine groups, which are susceptible sites to electrophilic attack by active chlorine species. The findings from this work stand out for prospective applications of anodic electrochemical oxidation to efficiently eliminate antibiotics with similar chemical structures in wastewater containing chlorides.

Electroactive biofilters outperform inert biofilters for treating surfactant-polluted wastewater by means of selecting a low-growth yield microbial community

Electrobioremediation is one of the most innovative disciplines for treating organic pollutants and it is based on the ability of electroactive bacteria to exchange electrons with electroconductive materials. Electroactive biofilters have been demonstrated to be efficient for treating urban wastewater with a low footprint; however, their application can be expanded for treating industrial wastewater containing significant concentrations (2.4 %vol) of commercial surfactants (containing lauryl sulfate, lauryl ether sulfate, cocamydopropyl betaine, and dodecylbenzene sulfonate, among others). Our electroactive biofilter outperformed a conventional inert biofilter made of gravel for all tested conditions, reaching removal rates as high as 4.5 kg COD/m3bed·day and withstood Organic Loading Rates as high as 9 Kg COD/m3·d without significantly affecting removal efficiency. The biomass accumulation reduced available bed volume in the electroactive biofilter just by 39 %, while the gravel biofilter decreased by 80 %. Regarding microbial communities, anaerobic and electroactive bacteria represented a substantial proportion of the total population in the electroactive biofilter. Pseudomonas was the dominant genus, while Cupriavidus, Shewanella, Citrobacter, Desulfovibrio, and Arcobacter were potential electroactive strains found in relevant proportions. The microbial community’s composition might be the key to understanding how high removal rates can coexist with limited biomass production, making electroactive biofilters a promising strategy to overcome classical biofilter limitations.

Facile green synthesis route for new ecofriendly photo catalyst for degradation acid red 8 dye and nitrogen recovery

This study novelty is that new photo catalyst prepared from sustainability low cost precursors. Dark red color hydrogel composites have been easily prepared from gelatin biopolymer using a simple sol–gel method. Gelatin doped by cobalt chloride, and silver nanoparticles (SNPs) in the presence of traces amount of sodium dodecyl sulfate surfactant and calcium chloride. Water-insoluble Gelatin composites are thermally stable photocatalysts for the degradation of toxic anionic acid red 8 dye. Promising photodynamic activity confirmed by fluorescence emission at λmax 650 nm. Optical absorption in Vis. light enhanced photo catalytic activity. Silver nanoparticles enhanced crystallinity, and improved optical properties and porosity. Dopants by CoCl2 and silver nanoparticles increased band gap of gelatin composites from (1.82 to 1.95) indicating interfacial charge separation. Low band gaps improved photo catalytic activity. Optical band gaps (Eg) lower than 2.0 eV indicates high catalytic activity in the photo degradation acid red 8 dye using Vis. light, wavelength 650 nm. Percent removal efficiency (%Re) of the dye at 500 ppm initial concentration, pH 1, contact time 30 min., and 0.20 g L−1 dose photo catalyst reached 95%. pH not affects removal efficiency. So, gelatin composites removed AR8 dye by photodegradation mechanism rather than adsorption due to photodynamic activity. Kinetics of photodegradation followed pseudo first order kinetic with rate constant k1 5.13 × 10−2 min.−1 Good electrical conductivity and magnetic properties (effective magnetic moment (µeff 4.11 B.M) improved dye degradation into simple inorganic species. Nutrients NH4+, and NO3− degradation products recovered by using alumina silicate clay via a cation exchange mechanism.

Fast-kinetics adsorption of a binary solution containing cationic and ionic pollutants using high-surface area activated carbon derived from macadamia nutshell

AbstractWastewater is characterized by multipollutant, and the presence of competitive adsorption could affect removal efficiency. Hence, the decontamination of water by adsorption in a multicomponent system allows an understanding of the practically and adsorbent efficiency. In this study, we present an analysis of the adsorption phenomena in a binary solution comprising compounds from distinct families, a dye, and an antibiotic, utilizing activated carbon obtained through a sustainable procedure. Locally available agricultural biowaste, specifically macadamia nutshell (MNS), served as a sustainable precursor to produce hierarchical porous activated carbon. The activation conditions were fine-tuned using the Box–Behnken experimental design. The resultant activated carbon was employed to remove a binary solution (BS) comprising the cationic dye, methylene blue (MB) and an ionic molecule amoxicillin (AMX) under specified conditions, including a pH range of 2 to 12, an initial concentration of BS ranging from 50 to 800 mg/L, and an adsorbent dosage within the range of 0.1 g to 0.3 g in a single adsorption system. The results revealed that higher temperatures adversely impacted the carbon yield, with a pronounced interaction effect observed between temperature and time. The activation temperature and K2CO3:precursor molar ratio predominantly influenced the textural and morphological properties of the activated carbon. Under optimal conditions (900 °C, 1 h, and a K2CO3:precursor ratio of 2:1), remarkably high-surface area (1225 m2/g), pore volume (0.801 cm3/g), and a nanopore size of 0.406 nm were achieved. In binary adsorption studies, R2-MNS demonstrated a maximum adsorption capacity of 578.925 mg/g. A pH above 4.5 produced an antagonistic effect on the removal of AMX due to competitive adsorption. Evaluation of three isotherm models demonstrated that the Khan isotherm best describes the affinity of BS to R2-MNS. The pseudo-second-order kinetic model best describes the data, indicating a chemisorption mechanism. The interparticle diffusion test revealed that the adsorbent exhibited very fast adsorption behaviour at the initial stage. Graphical abstract

Applying a nanocomposite hydrogel electrode to mitigate electrochemical polarization and focusing effect in electrokinetic remediation of a Cu- and Pb-contaminated loess

Inappropriate handling of copper (Cu) and lead (Pb)-containing wastewater resulting from metallurgical and smelting industries in Northwest China encourages their migration to surrounding environments. Their accumulation causes damage to liver and kidney function. The electrokinetic (EK) technology is considered to be an alternative to traditional remediation technologies because of its great maneuverability. The EK remediation is accompanied by the electrode polarization and the focusing effect toward affecting removal efficiency. In this study, a nanocomposite hydrogel (NCH) electrode was proposed and applied to the EK remediation of Cu- and Pb-contaminated loess. The mechanical, adsorption capacity, adsorption kinetics, and electrochemical properties of the NCH electrode were investigated in detail, followed by microscopic analyses of Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Raman spectrometer. Results showed that the enhancement of the mechanical properties of the NCH electrode was attributed to the crosslinks of graphene nanoparticles, calcium alginate, and hydrogen bonds, while the Cu or Pb adsorption by the NCH electrode was in a chemisorption manner. The second layer formation might address the increase in adsorption capacity with increasing temperature. These results highlight the relative merits of the NCH electrode and verify the potential of applying the NCH electrode to the EK remediation of Cu- and Pb-contamianted loess.

Sorption behavior of chitosan nanoparticles for single and binary removal of cationic and anionic dyes from aqueous solution.

In this study, chitosan nanoparticles (ChNs) were used as an adsorbent for single and simultaneous uptake of cationic (methylene blue (MB)) and anionic (methyl orange (MO)) dyes. ChNs were prepared based on the ionic gelation method using sodium tripolyphosphate (TPP) and characterized by zetasizer, FTIR, BET, SEM, XRD, and pHPZC. The studied parameters that affect removal efficiency included pH, time, and dyes' concentration. The results showed that in single-adsorption mode, the removal of MB is better in alkaline pH, contrary to MO uptake which presents higher removal efficiency in acidic media. The simultaneous removal of MB and MO from the mixture solution by ChNs could be achieved under neutral conditions. The adsorption kinetic results showed that adsorption of MB and MO for both single-adsorption and binary adsorption systems comply with the pseudo-second-order model. Langmuir, Freundlich, and Redlich-Peterson isotherms were used for the mathematical description of single-adsorption equilibrium, while non-modified Langmuir and extended Freundlich isotherms were used to fit the co-adsorption equilibrium results. The maximum adsorption capacities of MB and MO in a single dye adsorption system were 315.01 and 257.05 mg/g for MB and MO, respectively. On the other hand, and for binary adsorption system, the adsorption capacities were 49.05 and 137.03 mg/g, respectively. The adsorption capacity of MB decreases in solution containing MO and vice versa, suggesting an antagonistic behavior of MB and MO on ChNs. Overall, ChNs could be a candidate for single and binary removal of MB and MO in dye-containing wastewater.

Factors impacting the behavior of phytoremediation in pesticide-contaminated environment: A meta-analysis

Phytoremediation provides substantial advantages, including eco-friendliness, cost-effectiveness, efficiency, and visual appeal. However, the current knowledge of the factors influencing phytoremediation in pesticide-contaminated environments remains limited. It is critical to understand phytoremediation and the factors affecting the variation in removal efficiency. In this study, we compiled 72 previous research articles to quantify plant-induced improvements in removal efficiency and identify factors that influence variations in phytoremediation behavior through meta-analysis. We observed a significant increase in the removal efficiency of phytoremediation compared to the control group which did not involve phytoremediation. Pesticides significantly affect removal efficiency in terms of their modes of action, substance group, and properties. Plants demonstrated higher efficiency in remediating environments contaminated with pesticides possessing lower molecular masses and log Kow values. Plant species emerged as a crucial determinant of variations in removal efficiency. Annual plants exhibited a 1.45-fold higher removal efficiency than perennial plants. The removal efficiencies of different plant types decreased in the following order: agri-food crops > aquatic macrophytes > turfgrasses > medicinal plants > forage crops > woody trees. The Gramineae family, which was the most prevalent, demonstrated a robust and consistent phytoremediation ability. This study offers a more comprehensive triangular relationship between removal efficiency, pesticides, and plants, expanding the traditional linear model. Our findings offer valuable insights into the behavior of phytoremediation in pesticide-contaminated environments and the factors determining its success, ultimately guiding further research toward developing strategies for higher removal efficiency in phytoremediation.

Performance of Anaerobic Membrane Bioreactor (AnMBR) with Sugarcane Bagasse Ash-based Ceramic Membrane treating Simulated Low-strength Municipal Wastewater: Effect of Operation Conditions.

The online version contains supplementary material available at 10.1007/s11270-023-06173-3.

Preparation of bionanomaterial based on green reduced graphene immobilized Ochrobactrum sp. FJ1: Optimization, characterization and its application

Biodegradation using free cells is limited to low cell density, biological activity, and subsequent cell collection and regeneration are difficult. Meanwhile the limitations of using graphene-based nanomaterials for the removing emerging contaminants are adsorption and required further regeneration. To address these problems, reduced graphene oxide (rGO) synthesized by green tea extract as the carrier served to immobilize Ochrobactrum sp. FJ1 to form a functional bionanomaterial (FJ1@rGO). Its function was to degrade 17beta-estradiol (E2). To obtain a highly functional bionanomaterial, response surface methodology (RSM) with central composite design (CCD) was deployed to evaluate the synthesis conditions, which guided the ability of FJ1@rGO to remove pollutants. Results show that inoculation amount and immobilization time greatly affect removal efficiency, and the efficiency in removing E2 utilizing the optimized FJ1@rGO reached 93.7 % within 10 days. This proved to be significantly higher than prior to optimization. To provide evidence for functional FJ1@rGO, a series of advanced characterization results confirmed that FJ1 was successfully immobilized on rGO. It appears that FJ1@rGO has: firstly, excellent removal effect on E1, BPA, and triclosan; and secondly, excellent recycling properties.

Green Nanoemulsion Water/Ethanol/Transcutol/LabM-Based Treatment of Pharmaceutical Antibiotic Erythromycin-Contaminated Aqueous Bulk Solution.

Contaminated wastewater released from hospital, domestic, and industrial sources is a major challenge to aquatic animals and human health. In this study, we addressed removal of erythromycin (ERN) from contaminated water employing water/ethanol/Transcutol/Labrafil M 1944 CS (LabM) green nanoemulsions as a nanocarrier system. ERN is a major antibiotic contaminant harming aquatic and human lives. Green nanoemulsions were prepared and evaluated for size, size distribution (measuring polydispersity index), stability, zeta potential, refractive index, and viscosity. Transmission electron microscopy (TEM) was used to visualize morphological behavior. The treated-water was analyzed for ERN by the spectroscopy, scanning electron microscopy-energy-dispersive X-ray analysis mode (SEM-EDX), and inductively coupled plasma-optical emission spectroscopy (ICP-OES) techniques. We studied factors (composition, size, viscosity, and time of exposure) affecting removal efficiency (%RE). The obtained green nanoemulsions (ENE1-ENE5) were stable and clear (<180 nm). ENE5 had the smallest size (58 nm), a low polydispersity index value (0.19), optimal viscosity (∼121.7 cP), and a high negative zeta potential value (-25.4 mV). A high %RE value (98.8%) was achieved with a reduced size, a high water amount, a low Capryol 90 content, and optimal viscosity as evidenced by the obtained results. Moreover, contact time had insignificant effect on %RE. UV-vis spectroscopy, SEM-EDX, and ICP-OES confirmed the absence of ERN from the treated water. Conclusively, ERN can easily be removed from polluted water employing green nanoemulsions prepared from the optimized excipients, and evaluated characteristics.

Influencia de la concentración inicial de cobre, pH y perlas compuestas reticuladas de alginato-quitosano y alginato-quitosano-Aspergillus australensis en la capacidad de adsorción y eficiencia de remoción de iones de cobre

Copper (Cu) is a toxic heavy metal whose concentration must be reduced to values under the environmental standard before discharges can be released into the environment. Due to its characteristics, using different adsorbents for biosorption is a convenient method for removing heavy metals. Alginate and chitosan are biopolymers that have shown high potential as adsorbents. This investigation discusses the influence of pH, initial concentration of copper (Co), and the type of immobilized bead in the adsorption capacity and removal efficiency of copper from synthetic solutions. FT-IR analysis showed cross-linked composite beads of alginate-chitosan (ICB) and alginate-chitosan-Aspergillus australensis (IBB) possess different functional groups. The analysis made with the kinetic models showed that the adsorption mechanism was governed by diffusion through interface and chemical adsorption. Adsorption capacity depends on pH and Co. Maximum average adsorption capacity was 4.46 mg/g at 600 mg/L and pH 4.5 for ICB. Statistical analysis demonstrated that Co, pH, and their interactions significantly affect removal efficiency. Besides, the highest removal efficiency was 36.18% ± 1.87 at pH 4.5, 150 mg/L for IBB. These biomaterials could be a potential adsorbent for removing copper from wastewater.

Adsorption coupling photocatalytic removal of gaseous n-hexane by phosphorus-doped g-C3N4/TiO2/Zn(OAc)2-ACF composites.

VOCs emission reduction in the petroleum and petrochemical industry is a hot and difficult topic at present. The single method may not be able to meet the actual treatment status. Therefore, the adsorption coupled photocatalytic degradation technology was used to remove VOCs. Phosphorus-doped carbon nitride (PCN) and PCN/TiO2 were prepared by hydrothermal synthesis and sol-gel method, and then PCN/TiO2/Zn(OAc)2-ACF composites were prepared by ultrasonic impregnation on zinc acetate modified activated carbon fibers (Zn(OAc)2-ACF). The removal efficiency of n-hexane by composite materials was explored in a self-made reactor, and the factors affecting removal efficiency, removal mechanism, and possible ways of degradation were investigated. The results showed that under the optimum reaction conditions (initial concentration of n-hexane 200mg/m3, space velocity 1000h-1, light intensity 24W, mass fraction of doped PCN 6%, loading twice, calcination temperature 450°C), PCN/TiO2/Zn(OAc)2-ACF composite has the highest removal efficiency of n-hexane (90.2%). The adsorption capacity of the composites after doping the P element was 215.3mg/g, which did not enhance the adsorption performance compared with that before doping, but the removal rate of n-hexane was higher. This showed that doping P element was helpful to enhance the photocatalytic activity of the composites.

Scaled-up multi-anode shared cathode microbial fuel cell for simultaneous treatment of multiple real wastewaters and power generation

Microbial fuel cell (MFC) is lauded for its capacity to valorize organic substrates in wastes, providing a solution to environmental pollution and energy crisis. While different types of organic substrates affect removal efficiency and current output, most MFCs are designed to only be able to utilize one type of wastewater. However, many real wastewater treatment sites generate more than one type of wastewater which hinders the installation of most MFCs. This study aimed to investigate the performance of the novel-designed multi-anode shared cathode MFC (MASC-MFC) compared with a standard single anode/cathode MFC (SAC-MFC) and the simultaneous treatment of different types of real wastewaters (sewage, slaughterhouse, and hospital) in one MFC unit. The MASC-MFC (9025 mW/m2 at 23.332 mA/m2) produced 1.7 times and 1.6 times higher in power density and current density and 2.2 times lower in internal resistance than the standard single anode/cathode MFC (SAC-MFC). A maximum COD removal efficiency of 62.7% was achieved with synthetic wastewater. Feeding the MASC-MFC with multiple real wastewaters decreased maximum power density 3.5 (2599 mW/m2) times and increased internal resistance 2.7 times. Stable current generation 1.575 mA was achieved over 300 h despite the different and complex wastewater physio-chemical compositions. The MASC-MFC achieved over 40% and approximately 30% coulombic efficiency independently in all the anode chambers irrespective of the type of real wastewater used, demonstrating the MASC-MFC's capacity to treat different real wastewaters with the added benefit of electricity production.

Remediation of PNP-contaminated groundwater using a modified CaO2/Fe(II) Fenton system: Reactive principles, degradation performance and potential pathways

Calcium peroxide (CP, CaO2), acting as a source of H2O2, was combined with Fe(II) to provide a novel modified Fenton system. The removal of p-nitrophenol (PNP) in groundwater as a model pollutant was investigated using this system while addressing effect of reagents on water quality, mechanism of reactive oxygen species formation, possible degradation pathways, impact of geochemistry and process parameters on the removal efficiency. The dissolved oxygen, oxidation-reduction potential, pH, electrical conductivity and H2O2 concentration in groundwater were all increased significantly due to the addition of CaO2 and Fe(II), especially in the early stage and under acidic conditions. Within 30 min, 96% of an initial 40 mg/L PNP contamination was removed using the optimum conditions, consisting of 250 mg/L CaO2, 50 mg/L Fe(II), an initial pH of 2.6, oscillation frequency of 170 rpm and temperature of 298 K. The batch experiments revealed that the initial pH and the Fe(II) and CaO2 concentrations all decisively affected removal efficiency, while the groundwater dynamics, temperature and illumination conditions had little effect. The presence of hydroxyl radicals (∙OH) and singlet oxygen (1O2) was confirmed by electron paramagnetic resonance spectroscopy. In addition, ∙OH quenching experiments indicated that the former rather than the latter played a major role in PNP removal. The generation of 1O2 in this system was also predicted by classical molecular orbital theory. These findings would provide useful technical support for the remediation of groundwater contamination.

Density-dependent ecosystem service delivery under shifting temperatures by dung beetles

Increases in the frequency and magnitude of suboptimal temperatures as a result of climate change are subjecting insects to unprecedented stresses. This may negatively affect their fitness and the efficiency of their ecosystem service provision. Dung beetles are ecosystem service providers: through feeding on and burying dung, they facilitate nutrient recycling, secondary seed dispersal, parasite control, soil bioturbation and dung decomposition. As such, prediction of how dung beetles respond to multiple anthropogenic environmental changes is critical for the conservation of ecosystem services. Here, we quantified ecosystem services via dung utilisation and dung ball production in three telecoprid species: Allogymnopleurus indigaceous, Scarabaeus zambezianus and Khepher prodigiosus. We examined ecosystem service efficiency factorially under different beetle densities towards different dung masses and under three temperature treatments (21 °C, 28 °C and 35 °C). Khepher prodigiosus, exhibited greatest dung utilisation efficiency overall across dung masses, compared to both S. zambezianus and A. indigaceous. Dung removal was exhibited under all the tested temperatures by all tested species, and therefore the sub-optimal temperatures employed here did not fully inhibit ecosystem service delivery. However, emergent effects among temperatures, beetle species and beetle density further affected removal efficiency: S. zambezianus and A. indigaceous utilisation increased with both warming and beetle density, whereas K. prodigiosus performance was less temperature- and density-dependent. Beetles also tended to exhibit positive density-dependence as dung supply increased. The numbers of dung balls produced differed across species, and increased with temperature and densities, with S. zambezianus producing significantly most balls overall. Our study provides novel evidence for differential density-dependent ecosystem service delivery among species across stressful temperature regimes and emergent effects for dung mass utilisation. This information is essential for biodiversity-ecosystem-function and is critical for the conservation of functionally efficacious species, with implications for natural capital conservation policy in rapidly changing environments.

Elimination of Arsenic (III) using Phaseolus Lunatus and Phaseolus Vulgaris as Natural Coagulants

In this analysis, the efficacy of adding coagulants such as Phaseolus lunatus and Phaseolus vulgaris (polymers) to the coagulation process during the treatment of arsenic aqueous solution to extract the arsenic metal was investigated. Experiments were carried out to evaluate the output of Phaseolus lunatus and Phaseolus vulgaris, both individually and in combination with arsenic, using the standard Jar test protocol. P.lunatus and P.vulgaris were given doses ranging from 1 to 3 gm. For P.lunatus and P.vulgaris, the (optimal) removal efficiency for total arsenic in the aqueous solution was obtained at 2gm. With chemical affinity between arsenic and coagulants used in this process, the valence state of arsenic may affect removal efficiency during the chemical coagulation process. pH is discovered to be a significant factor that has a direct or indirect impact on results. By overcoming the isoelectric point, the complex formed by the interaction of the inorganic pollutant and organic coagulant may aid in the removal of arsenic at pH 9 and 8. P.lunatus and P.vulgaris had optimised arsenic initial concentrations of 57.1µg/L and 42.6µg/L, respectively. The coagulation mechanism is more prevalent in water treatment, as shown by the above findings.

Factors affecting Removal Efficiency of Intracanal Medicaments - A Literature Review

Factors affecting Removal Efficiency of Intracanal Medicaments - A Literature Review

Phenanthrene removal from the contaminated soil using the electrokinetic-Fenton method and persulfate as an oxidizing agent

Remediation of soils contaminated with hydrocarbon materials is of particular importance due to their association with food chain. One of the remediation methods, which has been taken into account in recent years by researchers, is the electrokinetic technique. In this study, the electrokinetic method was used in combination with the Fenton technique to remove phenanthrene from clay soil. Oxidizing agent and catalyst used in the Fenton technique greatly influenced the efficiency of the remediation process. To investigate the effect of these two factors on the remediation process, it was made use of three different types of electrodes as catalyst, including graphite, iron, and copper, as well as hydrogen peroxide and sodium persulfate with different concentrations as oxidizing agent. During the 9 experiments designed, factors affecting removal efficiency, such as remediation time, electric current intensity, electroosmotic flow rate, and pH of the cathode and anode reservoirs were also investigated. Overall, the use of the electrokinetic-Fenton method with 15% hydrogen peroxide and copper electrode exhibited a 100% increase in the process efficiency over the same time period required to perform the conventional electrokinetic method and removed 93% of the soil phenanthrene, these findings indicated that combining the Fenton technique with the electrokinetic method enhanced the efficiency of this method in removing organic pollutants from the soil. Also, the use of sodium persulfate as an oxidizing agent in the electrokinetic method increased the removal efficiency by more than 95% over the half time period required to perform the conventional electrokinetic method.

Removal of nutrients from domestic wastewater using constructed wetlands: assessment of suitable environmental and operational conditions

Constructed wetlands (CWs) offer an eco-friendly wastewater treatment technology primarily for decentralized locations. They support a dense growth of macrophytes which help in the reduction of water velocity, development of conducive microenvironments and provide adherence sites for microorganisms to develop biofilms. Several environmental and operational parameters are crucial for the efficient working of CWs wherein, suitable pH, temperature and dissolved oxygen (DO) are more significant. The performance of CWs has been enhanced significantly through effluent recirculation and artificial aeration. Removal of phosphorus proceeds via adsorption within media material, sedimentation, cation exchange, precipitation and uptake by macrophytes and the removal of nitrogen occurs mainly by microbial communities and macrophytic uptake. In colder climates, the bioaugmentation of microbial communities is required to increase the treatment efficiency. Various previous research findings showed several aspects of CWs that could potentially affect removal efficiency of the nutrients from the wastewater. However, maintaining suitable environmental and operational conditions for the effective operation of CWs remains a challenge. Therefore, the objectives of this review-based study are to provide the most favorable environmental conditions for the effective operation of CWs. Recent developments in operational and working parameters of CWs focusing on the selection of macrophytes and substrate material, carbon source, feeding mode, hydraulic loading rates and retention times are discussed. The study also provides effect of effluent recirculation, bioaugmentation of microbes, suitable C/N ratio and artificial aeration for the domestic wastewater treatment.

The adsorption of Mn(II) by insolubilized humic acid

The eco-friendly and non-toxic natural organic substance, insolubilized humic acid (IHA), was used to remove Mn(II) from aqueous solutions. The adsorption characteristics were studied through a series of static adsorption tests. The results show that conditions such as the dose, the pH of the solution and the initial concentration of Mn(II) all affect removal efficiency, and the optimal pH value was 5.5. The sorption process for Mn(II) on IHA conforms to the pseudo-second-order adsorption kinetic model and intra-particle diffusion is not the only factor affecting the adsorption rate. Both Langmuir and Freundlich models can describe this adsorption behavior, and the experimental maximum adsorption capacity of IHA was 52.87 mg/g under optimal conditions. The thermodynamic analysis of adsorption shows that the adsorption process is a non-spontaneous endothermic physical reaction. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to characterize the samples, it was found that as IHA successfully adsorbed Mn(II), the surface morphology of IHA changed after the adsorption reaction. The adsorption mechanism for Mn(II) on IHA is to provide electron pairs for carboxyl, phenolic hydroxyl and other functional groups to form stable complexes with Mn(II).