Wide Range Of Initial pH Research Articles

Photo-assisted peroxymonosulfate activation via 2D/2D heterostructure of Ti3C2/g-C3N4 for degradation of diclofenac

In this paper, a two dimensional/two dimensional (2D/2D) heterostructure of Ti3C2/g-C3N4 (T/CN) was constructed and used to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF) in water in the presence of light illumination. Compared with single photocatalytic process by T/CN (0.040/min) and with pure g-C3N4 nanosheets in PMS system (0.071/min), 5.0 and 3.0 times enhanced activities were achieved in the T/CN-PMS system at optimum Ti3C2 (1.0 wt%) loading under light illumination (0.21/min). Moreover, the decomposing processes of DCF in T/CN-PMS system were applicable in a wide initial pH range (3∼14), therefore, overcoming the limitation of pH dependence in traditional PMS system. Based on the synergistic effect of photocatalysis and PMS oxidation processes, the 1O2 was generated as primary reactive species for the removal of DCF in T/CN-PMS system. The DCF degradation mechanism was further proposed through the results of liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations.

Hydrothermal synthesis of FeS2 as a highly efficient heterogeneous electro-Fenton catalyst to degrade diclofenac via molecular oxygen effects for Fe(II)/Fe(III) cycle

In this study, we demonstrated that hydrothermal synthesized FeS2 was highly efficient to catalyze the H2O2 decomposition for diclofenacsodium (DCF) degradation in a wide range of initial pH (3–9) by heterogeneous electro-Fenton (EF) process, and this “Pyrite-EF” showed a better performance for the mineralization of DCF in comparison with the classic EF process. Effect of pyrite content on the hydroxyl radicals generation and iron dissolution produced by the decomposition of hydrogen peroxide (H2O2), and applied current density on the degradation kinetics and mineralization efficiency were studied. Moreover, toxicity assessment by means of microtox method showed the solution toxicity was removed after treatment. Experimental results revealed that the enhancement of DCF degradation rate in the Pyrite-EF process was attributed to the molecular oxygen activation induced by more surface bound ferrous ions on FeS2, generating superoxide anions to accelerate the Fe(II)/Fe(III) cycle on the FeS2 surface, which favored the H2O2 decomposition to generate more hydroxyl radicals for the DCF degradation via a heterogeneous EF-like process. These findings could provide some new insights into the molecular oxygen activation induced by FeS2 and the subsequent heterogeneous Pyrite-EF degradation of organic pollutants from wastewater.

Efficiency and mechanisms of simultaneous removal of Microcystis aeruginosa and microcystins by electrochemical technology using activated carbon fiber/nickel foam as cathode material

The significant removal efficiency of microcystis aeruginosa was presented using Pt/Ti anode and activated carbon fiber/nickel foam (ACF/Ni) cathode by addition of Fe2+ slightly in a wide range of initial pH (3–9). Results showed that about 93% of the Microcystis aeruginosa cells were removed within 15 min for Pt/Ti-ACF/Ni–Fe2+ system. Dosage of Fe2+, current density, and initial pH had remarkable effects on the removal efficiency of microcystis aeruginosa. The mechanism of algae removal in the Pt/Ti-ACF/Ni–Fe2+ electrochemical system was revealed by the comparison between Pt/Ti-ACF/Ni–Fe2+ process and classical Fenton process, the analysis on Microcystis aeruginosa and ACF/Ni by SEM, the specific surface area and pore size analysis of ACF, and the determination of UV254, OD620 and microcystin-LR (MC-LR). Results showed that the main mechanism of this system was the electro-Fenton process, which was accompanied by electro-adsorption, electro-floatation, and electro-coagulation process. And the cooperation mechanism on the electrochemical removal system was further speculated. With the breakdown of algal cells during the electrolysis, the MC-LR and other substances released from the cells were effectively degraded. Besides, the new cathode exhibited favorable and stable reusability. This study built up a high-efficiency algae removal system, which broke through the limits of narrow working pH range and large consumption of exogenous chemicals in electro-Fenton process.

Zinc solubilization characteristics of efficient siderophore-producing soil bacteria

Iron and zinc are two essential micro-nutrients for plant growth and development. Therefore, isolation of siderophores-producing and zinc-solubilizing rhizobacteria involved in bio-availability of these elements is of great interest. In this study, soil samples collected from slightly alkaline soil types were screened for high levels of siderophore secretion and zinc solubilization. Among positive colonies, three isolates, named F21A, F37 and F38, were able to secrete siderophore at high levels, ranged between 200 and 300 μM/liter. A close association was observed between siderophore production capability and growth rate as an indicator of active metabolism. Siderophore production was closely correlated with the level of zinc ion released into the medium as well. All three siderophore producing isolates were able to withstand temperature as high as 37°C, high concentration of NaCl (up to 2.5%) and a wide range of initial pH from 6 to 9 while hydrolyzing Zn compounds actively. One of the isolates, F21A, tolerated the presence of 200 mgl-1 of zinc. Biochemical and molecular characteristics are indicative that these isolates are Pseudomonas japonica. As experienced in a greenhouse experiment, inoculation with the F21A and F37 isolates significantly increase the plants height, fresh and dry weight of corn with compared to control. These findings demonstrated that the potential of P. japonica strains as plants growth promoting rhizobacteria (PGPR) in iron and zinc deficient soils.

Mo0 and Mo4+ bimetallic reactive sites accelerating Fe2+/Fe3+ cycling for the activation of peroxymonosulfate with significantly improved remediation of aromatic pollutants.

In Fe2+/peroxymonosulfate (PMS) activation system, the slow cycle rate of Fe3+/Fe2+ has been considered to be the limiting step in the remediation of organic contaminants. In this paper, commercial molybdenum (Mo) powder is employed as the cocatalyst in Fe2+/PMS system, which can significantly accelerate the Fe3+/Fe2+ cycling efficiency by the exposed bimetallic active sites of Mo4+ and Mo0, and the process is accelerated as the amount of Mo powder increased. The Mo cocatalytic Fe2+/PMS system exhibits an enhanced performance for the activation of PMS and the removal of different aromatic pollutants including dyes, phenolic pollutants and antibiotics, in a wide pH range of 4.0-9.0. Importantly, Mo powder exhibits excellent cycle performance in the PMS activation system, and rhodamine B (RhB) can be removed within 10min even after 5 cycles. Electron paramagnetic resonance (EPR) prove that the sulfate radicals (SO4-) is the major reactive oxides species in the PMS activation, the increase of Fe2+ content induced by the cocatalytic effect of Mo powder can effectively promote the production of SO4- and increase the utilization of PMS. In addition, to observe the process of pollutant removal more intuitively, HPLC-MS is used to analyze the decomposing pathway of RhB and sulfadiazine in Mo+FeSO4+PMS system. It is believed that this research provides a new idea for the efficient activation of PMS by iron ions in a wide initial pH range, which is expected to be applied to the treatment of large-scale industrial wastewater.

Meat & bone meal (MBM) incineration ash for phosphate removal from wastewater and afterward phosphorus recovery

Abstract Meat & bone meal ash (MBMA), the bottom ash collected from a UK industrial-scale incinerator in a power plant with meat & bone meal (MBM) as the mono-energy source, was characterised in terms of its elemental and crystalline compositions. MBMA has high phosphorus concentration (13.48% P, or 31.31% P2O5) and low hazardous element content. The phosphorus present in it, which mainly in the form of hydroxyapatite (HAP), would only release at initial acid leaching pH lower than 2.7 at solid: liquid ratio of 1:1 (wt.). Then MBMA was used for P removal from synthetic phosphate wastewater in batch adsorption experiments. The removal of P can be completed over a wide range of initial pH within an hour with removal capacity ∼115 mg g−1 being achieved. The main P removal mechanisms can be explained by HAP precipitation because of the MBMA seeding effect. After the wastewater treatment process, P content of the ash was increased from 13.48% to 16.18% (or 37.06% P2O5), and the acid consumption for P recovery from the ash after wastewater treatment was reduced by 20% compared with the original MBMA. The acid consumption under optimized conditions was as low as ∼3 mM H+/mM P. The application of MBMA for P-containing wastewater treatment not only offered the benefit of wastewater remediation, but it also contributed greatly to the feasibility of using MBMA for P recovery.

Enhancement of ciprofloxacin degradation in the Fe(II)/peroxymonosulfate system by protocatechuic acid over a wide initial pH range

The appearance of large amounts of antibiotics in drinking water and wastewater treatment plants has attracted extensive interest because of the potential resultant environmental and biological risks. Although the Fe(II)/peroxymonosulfate (PMS) system provides a feasible method for antibiotic degradation, the narrow pH range in which it operates and the resultant iron precipitation limit its use. In this study, protocatechuic acid (PCA) was introduced into the Fe(II)/PMS system to improve the system performance. Ciprofloxacin (CIP) was used as the probe reagent. Compared with the Fe(II)/PMS system, the Fe(II)/PCA/PMS system performed better for CIP degradation. This enhanced degradation was attributed mainly to the reduction and chelating ability of the PCA, which enhanced radical generation by accelerating the transformation from Fe(III) to Fe(II) and by forming the PCA-Fe chelate. The Fe(II)/PCA/PMS system also showed a superior degradation ability, even under alkaline conditions, because the PCA-Fe chelate protected iron from precipitation and released hydrogen ions continuously in the process. The electron paramagnetic resonance and alcohol-quenching tests indicated that sulfate and hydroxyl radicals existed in this system and two main CIP degradation pathways were proposed from the liquid chromatography-mass spectrometry results. This work aims to provide new ideas for refractory organics treatment.

Synthesis and characterization of graphene oxide-doped nano-hydroxyapatite and its adsorption performance of toxic diazo dyes from aqueous solution

In this study, graphene oxide-doped nano-hydroxyapatite (nHAp@GO) composite was synthesized via a simple in-situ one-pot method and was used as an adsorbent for the removal of toxic diazo dyes, Congo Red (CR) and Trypan Blue (TB), in water. A remarkable adsorption capacity for CR (48.5mg/g) and TB (41.0mg/g) were shown on the surface of nHAp@GO (2g/L), respectively, and was much higher than those of bare nHAp or GO. After doping of GO on nHAp, the specific surface area of nHAp was increased by 2.5 times. The presence of sulphur peak in EDX spectrum and SO stretching vibration peak in FTIR confirmed the adsorption of dyes on the surface of nHAp@GO composite. After the adsorption process, the shifting of d(100) spacing of nHAp confirmed the loading of bulky organic moieties on nHAp@GO composite. Maximum CR and TB dyes adsorption occurred in a wide range of initial pH between 3.0 and 10.0. The adsorption of both CR and TB dyes are due mainly to the electrostatic interaction, π−π stacking interaction, hydrophobic interaction, and hydrogen bonds between dyes and nHAp@GO composite. The nHAp@GO nanocomposite was recycled up to three times at the sustained efficiency after washing with ethanol solution. We believe that such multifunctional material developed in this study will be effectively used for the depollution of toxic diazo dyes in practical applications.

Enhancing surface corrosion of zero-valent aluminum (ZVAl) and electron transfer process for the degradation of trichloroethylene with the presence of persulfate

Though covered with a compact oxide film, unmodified zero-valent aluminum (ZVAl), showed a significant synergistic effect combined with persulfate (PS) for the degradation of trichloroethylene (TCE) over a wide initial pH range (3.00–10.00) without any induction period. In ZVAl/PS system, there are oxidizing species, including PS, O2, H2O and the target contaminant TCE, which will compete for electrons released from ZVAl corrosion. In order to really understand the reaction mechanism, in this work, the complicated surface corrosion and electron transfer processes for TCE degradation were deeply explored. Firstly, by the characterizations of SEM-EDS, TEM, size distribution, N2 adsorption–desorption isotherms, XRD and XPS, we found that pristine ZVAl was a core–shell structure and during the reaction the core was corroded and oxidized to Al-(hydr)oxide. After reaction, the oxide film was not directly removed, but became rougher, causing the increase of particle size, specific surface area, total pore volume and average pore size of ZVAl. The addition of PS can indeed activate ZVAl surface and accelerate ZVAl corrosion rate, and acidic environment is more conducive to the corrosion, which is opposite to the case without PS. Secondly, the dominant active species and electron transfer processes for TCE degradation were identified. SO4− was generated through electron transfer from ZVAl to PS directly. O2 may be involved in the process at acidic pH by forming O2− and H2O2. Hence, rather than the reductive removal by electron released from ZVAl, complete dechlorination and partial mineralization of TCE could be achieved, due to the high solubility and standard redox potential of PS which has more chance to capture electron and to the highly oxidative capacity of generated radicals.

Mackinawite (FeS) activation of persulfate for the degradation of p-chloroaniline: Surface reaction mechanism and sulfur-mediated cycling of iron species

Among the numerous iron-based materials for persulfate (PS) activation, mackinawite (FeS) particles have gained considerable interest as a ubiquitous natural mineral due to their high reactivity. However, the iron and sulfur co-mediated reaction mechanism of PS activation by FeS remains ambiguous. In this study, FeS was applied as a catalyst to activate PS for p-chloroaniline (PCA) degradation and mineralization over a wide initial pH range (3.0–11.0). The reaction was found to follow pseudo-first-order kinetics, with rate constants ranging from 0.0044 to 0.0144min−1. The reaction mechanism was elucidated by electron spin resonance (ESR) and quenching studies. A heterogeneous activation mechanism, in which surface Fe(II) species activated PS to produce OHads and SO4−ads, controlled by surface reaction and diffusion was proposed, whereas OHfree and SO4−free diffusing from the FeS surface were mainly responsible for PCA degradation. The sulfur-mediated cycling of iron species was investigated by comparing PS activation by zero-valent iron (ZVI) and FeS, exogenous Fe(III) addition and X-ray photoelectron spectroscopy (XPS). The results suggested that Fe(II) and S(-II) experienced independent oxidations and that S(-II) species could regenerate Fe(II) from Fe(III) at the FeS surface. Therefore, the S(-II)-promoted Fe(II)/Fe(III) cycle resulted in less PS decomposition but a higher PCA mineralization efficiency. The findings of this study elucidated the novel surface activation mechanism of PS by FeS and provided useful information for utilizing FeS to remediate contaminated water.

Synthesis and properties of a high-capacity iron oxide adsorbent for fluoride removal from drinking water

A novel iron oxide adsorbent with a high fluoride adsorption capacity was prepared by a facile wet-chemical precipitation method and ethanol treatment. The ethanol-treated adsorbent was amorphous and had a high specific surface area. The adsorption capacity of the treated adsorbent was much higher than that of untreated adsorbent. The Langmuir maximum adsorption capacity of the adsorbent prepared at a low final precipitation pH (≤9.0) and treated with ethanol reached 60.8mg/g. A fast adsorption rate was obtained, and 80% of the adsorption equilibrium capacity was achieved within 2min. The adsorbent had high fluoride-removal efficiency for water in a wide initial pH range of 3.5–10.3 and had a high affinity for fluoride in the presence of common co-anions. The ethanol treatment resulted in structure transformation of the adsorbent by inhibiting the crystallization of the nano-precipitates. The adsorption was confirmed to be ion exchange between fluoride ions and the hydroxyl groups on the adsorbent surface.

Protonema suspension cultures of the medicinal moss Polytrichum juniperinum

The moss Polytrichum juniperinum was widely used by native North Americans and in traditional Chinese medicine to treat several illnesses including burns, wounds, bleeding, fever, kidney stones, and gallstones. This paper reports the efficient establishment of a protonema suspension culture of this moss and evaluation of key factors such as culture medium, trophic condition, initial pH, and inoculum size for increasing biomass production, which has scarcely been studied in this type of biological system. No significant differences were found for the maximum specific growth rate (μmax~0.09 d−1) and the total phenolic content between MS, Knop, and PPNH4 media, although an effect on tissue differentiation was observed. Growth rate in a mixotrophic condition was (μmax 0.27 d−1) three times greater than in autotrophic and heterotrophic conditions, reaching high cell densities (~11 g DW L−1). Moreover, simple sugars were secreted into the medium during the growth phase. P. juniperinum protonema cultures tolerated a wide initial medium pH range (4.5–8). The tissue growth index significantly decreased from ~7.7 to 1.9 with increased inoculum size (45–300 mg DW L−1) under photoautotrophic conditions. Similar responses were obtained under mixotrophic conditions with different sucrose concentrations (15–45 g L−1), but no responses to sucrose concentration and inoculum sizes were seen under heterotrophic growth conditions. Finally, this high cell density culture of P. juniperinum is suitable for further studies aimed at exploring and establishing a production platform for high-value secondary metabolites.

Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide.

Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3–10). The optimum conditions for the removal of Cr(III) were found to be at pH 4–6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent.

Adsorptive removal of fluoride from aqueous solutions using Al-humic acid-La aerogel composites

A novel and environmental friendly aerogel composite was synthesized by freeze-drying method using humic acid as low cost starting material. The as-prepared aluminum-humic acid-lanthanum (Al-HA-La) aerogel composites were fully characterized by nitrogen adsorption-desorption, SEM, EDX, XRD, FTIR and TGA Then, the adsorption behaviors of fluoride on Al-HA-La adsorbent were investigated systematically, including the influence of initial pH, adsorption kinetics, adsorption isotherms, desorption study, etc. Batch adsorption experimental results showed that the high fluoride removal of Al-HA-La was obtained in a wide initial pH range from 5 to 11. The adsorption equilibrium was achieved within 40min (pH=7.0), and the adsorption kinetics could be well fitted by the pseudo-second-order model. The adsorption isotherms could be well described by the Langmuir isotherm model and the maximum adsorption capacity calculated from Langmuir model was high up to 50mgg−1 at 298K (pH=7.0). Moreover, the co-existing of other anions and cations showed limited influence on the adsorption of fluoride on Al-HA-La. Furthermore, the fluoride adsorbed on Al-HA-La could be effectively desorbed using 10−2molL−1 NaOH, and the desorption efficiency was as high as 90%.

Magnetic calcinated cobalt ferrite/magnesium aluminum hydrotalcite composite for enhanced adsorption of methyl orange

A novel environment friendly adsorbent, magnetic calcinated cobalt ferrite/magnesium aluminum hydrotalcite composite (CoFe2O4/MgAl-LDO) was prepared through coprecipitation method and employed for methyl orange (MO) removal from aqueous solutions. The physicochemical properties of CoFe2O4/MgAl-LDO were characterized and its adsorption properties for MO removal under different conditions were investigated systematically. The results indicated that the adsorbent exhibited a high MO removal efficiency in a wide range of initial pH of 2.0–12.0 and high selectivity for MO versus common co-existing ions. The MO adsorption rate of the adsorbent was very fast, and the adsorption kinetics followed pseudo-first-order model. The adsorption isotherm could be well fitted in Langmuir model, while the maximum adsorption capacity was found to be 1219.5 mg/g at pH 6.0, which was much higher than the MO adsorption capacity of for most reported adsorbents. Thermodynamics data revealed the exothermic and spontaneous nature of the adsorption process. The regeneration of the adsorbent could be easily achieved through thermal treatment. After three cycles, the MO removal efficiency of CoFe2O4/MgAl-LDO still remained high. The efficient MO removal and easy magnetic separation makes CoFe2O4/MgAl-LDO be a promising adsorbent for effective removal of dyes from aqueous solutions.

Enhancement of Fenton degradation by catechol in a wide initial pH range

Abstract Enhancement of Fenton degradation by catechol was investigated in a wide initial pH range. Catechol could be degraded effectively within an initial pH of 3.0–9.0. The removal ratio of total organic carbon at neutral initial pH was higher than that under acidic conditions. Catechol degradation was enhanced because of the formation of catechol–Fe complexes. The coordination ratio between catechol and iron ions increased as the pH increased from 3.0 to 9.0. The formation of iron complexes not only inhibited iron precipitation at high pH values but also favored the release of H+. Dimethyl phthalate was degraded in the Fenton reaction with Fe(II) ion and Fe(OH)3 as iron sources in the presence of catechol–Fe complexes. The enhanced degradation could be due to decrease in pH, acceleration of the Fe(III)/(II) redox cycle, increase in dissolved Fe concentration, and rapid consumption of H2O2. This study proposes a mechanism through which catechol enhances Fenton degradation.

Hydrothermal Synthesis of FeS2 as a High-Efficiency Fenton Reagent to Degrade Alachlor via Superoxide-Mediated Fe(II)/Fe(III) Cycle

In this study, we demonstrate that hydrothermally synthesized FeS2 (syn-FeS2) is highly efficient at catalyzing the H2O2 decomposition for alachlor degradation at a wide range of initial pH (3.2-9.2). The alachlor degradation rate of syn-FeS2 heterogeneous Fenton system was almost 55 times that of its commercial pyrite (com-FeS2) counterpart at an initial pH of 6.2. Experimental results revealed that the alachlor oxidation enhancement in the syn-FeS2 Fenton system was attributed to the molecular oxygen activation induced by more surface-bound ferrous ions on syn-FeS2. The molecular oxygen activation process could generate superoxide anions to accelerate the Fe(II)/Fe(III) cycle on the syn-FeS2 surface, which favored the H2O2 decomposition to generate more hydroxyl radicals for the alachlor oxidation. It was found that the hydroxyl radicals generation rate constant of syn-FeS2 Fenton system was 71 times that of its com-FeS2 counterpart, and even 1-3 orders of magnitude larger than those of commonly used Fe-bearing heterogeneous catalysts. We detected the alachlor degradation intermediates with gas chromatography-mass spectrometry to propose tentatively a possible alachlor degradation pathway. These interesting findings could provide some new insights on the molecular oxygen activation induced by FeS2 minerals and the subsequent heterogeneous Fenton degradation of organic pollutants in the environment.

Adsorption of drinking water fluoride on a micron-sized magnetic Fe3O4@Fe-Ti composite adsorbent

A micron-sized magnetic adsorbent (MMA) for fluoride removal from drinking water was prepared by spray drying and subsequent calcination of a magnetic Fe3O4@Fe-Ti core–shell nanoparticle slurry. The MMA granules had high mechanical strength and stability against water scouring, can be easily separated from the water by a magnet, and had a high selectivity for fluoride versus common co-existing ions and high fluoride removal efficiency in a wide range of initial pH of 3–11. Abundant hydroxyl groups on the MMA surface acted as the active sites for fluoride adsorption, which resulted in a high affinity of the MMA for fluoride. The pH in the adsorption process affected the adsorption significantly. At neutral initial pH, the adsorption isotherm was well fitted with the Langmuir model, and the maximum adsorption capacity reached a high value of 41.8mg/g. At a constant pH of 3, multilayer adsorption of fluoride occurred due to the abundant positive surface charges on the MMA, and the adsorption isotherm was well fitted with the Freundlich model. The MMA had a fast adsorption rate, and adsorption equilibrium was achieved within 2min. The adsorption kinetics followed a quasi-second order model. The regeneration of the MMA was easy and fast, and can be completed within 2min. After 10 recycles, the fluoride removal efficiency of the MMA still remained high. These properties showed that the MMA is a promising adsorbent for fluoride removal.

Simultaneous removal of Cd(II) and Sb(V) by Fe–Mn binary oxide: Positive effects of Cd(II) on Sb(V) adsorption

The coexistence of cadmium ion (Cd(II)) and antimonate (Sb(V)) creates the need for their simultaneous removal. This study aims to investigate the effects of positively-charged Cd(II) on the removal of negative Sb(V) ions by Fe–Mn binary oxide (FMBO) and associated mechanisms. The maximum Sb(V) adsorption density (Qmax,Sb(V)) increased from 1.02 to 1.32 and 2.01mmol/g in the presence of Cd(II) at 0.25 and 0.50mmol/L. Cd2+ exhibited a more significant positive effect than both calcium ion (Ca2+) and manganese ion (Mn2+). Cd2+ showed higher affinity towards FMBO and increased its ζ-potential more significantly compared to Ca2+ and Mn2+. The simultaneous adsorption of Sb(V) and Cd(II) onto FMBO can be achieved over a wide initial pH (pHi) range from 2 to 9, and QSb(V) decreases whereas QCd(II) increases with elevated pHi. Their combined values, as expressed by QSb(V)+Cd(II), amount to about 2mmol/g and vary slightly in the pHi range 4–9. FTIR and XPS spectra indicate the significant synergistic effect of Cd(II) on Sb(V) adsorption onto FMBO, and that little chemical valence transformation occurs. These results may be valuable for the treatment of wastewater with coexisting heavy metals such as Cd(II) and Sb(V).

Removal of phosphate from wastewaters for further utilization using electrocoagulation with hybrid electrodes – Techno-economic studies

The electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30mg/l) was optimized, followed by successful scale-up experiments. The optimum process conditions (96% phosphate removal) for laboratory-scale SSW were found to be: anode/cathode=Al/Fe (although Fe/Al performed similarly), initial pH=5, current density=100A/m2, treatment time=15min, supporting electrolyte=1.0g/l NaCl and electrode gap=7mm.Real industrial phosphate-containing mining wastewater (MWW) and dairy wastewater (DWW) were also treated with EC, with high pollutant removal efficiencies (optimal phosphate removal of 79% and 93% in 30min and 60min, respectively) achieved over the wide initial pH range studied. Electricity consumption and operating costs values in optimum conditions were low for all wastewaters: 0.75kWh/m3 and 0.17€/m3 for SSW (laboratory scale), 2.11kWh/m3 and 0.28€/m3 for MWW, and 1.46kWh/m3 and 0.31€/m3 for DWW. To summarize, the feasibility of using EC in removing phosphate from the wastewater types studied was proven. Utilization of the resulting EC sludge – a potentially valuable phosphorus source in the future (especially in granulated bio ash-based fertilizer products) – was also studied and is discussed.