Optimum Removal Efficiency Research Articles

Biosorptive removal of nitrophenol from aqueous solution using ZnCl2-modified groundnut shell: optimization, equilibrium, kinetic, and thermodynamic studies

This study investigated the viability of using waste groundnut shells (GSs) to produce efficient biosorbent capable of removing nitrophenol from aqueous solution. Waste GSs were washed thoroughly, dried, reduced to 2 mm particle size, and activated with ZnCl2. The surface and physical properties (moisture and ash content) of the activated GSs (AGSB) were characterized using Fourier transform infrared spectrometer (FTIR), and standard methods. Biosorption of nitrophenol was optimized using Box–Behnken design (BBD). Analysis of the optimization processes was carried out using statistical tools embedded in the Design Expert software (10.0.1). Batch biosorption was conducted to generate data to determine suitable adsorption isotherm models, adsorption kinetics models, and adsorption thermodynamics. The FTIR spectra of AGSB indicate a major shift in the functional groups after the activation process. The moisture and ash content of AGSB were 9.0% and 3.1%, respectively. The optimum adsorption capacity (AC) and removal efficiency (RE) obtained at 20 mg/L, 80 min, and 1.6 g were 7.888 mg/g and 90.62%, respectively. The AC and RE were well suited to quadratic models with correlation coefficient (R2) of 0.9853 and 0.9914, respectively. Langmuir isotherm and pseudo-second-order kinetic models with R2 of 0.999 and 0.9843 were most suitable. The enthalpy, entropy, and Gibb’s free energy were in the ranges m − 20.46 to − 4.36, 20.14 to 86.17, and − 21.49 to − 5.02 kJ/mol, respectively. This study demonstrated the effectiveness of AGSB as biosorbent for wastewater treatment, thus facilitating the conversion of solid wastes for the amendment of nitrophenol concentration in the wastewater stream.

Photocatalytic degradation of Rhodamine-B under visible light region by ZnO nanoparticles loaded on activated carbon made from longan seed biomass

In the present study, the synthesis of ZnO/LSAC through pyrolysis of the carbonized material prepared from longan seed, zinc acetate in alkaline medium. The obtained materials was characterized by means of XRD, SEM, TEM, BET and UV-Vis-DRS. The XRD patterns of ZnO/LSAC nanocomposites were assigned to wurtzite structure of ZnO with crystallite size about 15 to 30 nm. SEM and TEM observations showed the spherical ZnO particles formed on the activated carbon. The band gap energy and specific surface area of ZnO/LSAC were found to be 2.79 eV and 294.4 m2/g, respectively. The photocatalytic activities of the prepared materials were evaluated for the degradation of Rhodamine B (RhB) dye. The removal of RhB was found to be pH dependent, and the optimized removal efficiency reached to 93.75% and the mineralization level was over 84,09% at initial RhB concentration of 40 mg.L-1 and pH 7 following 120 min under visible-light illumination. The kinetic studies showed the decolorization of RhB followed pseudo first-order kinetics with the rate constant were determined kapp = 1.67x10-2 min−1.

Treatment of Zn2+ in wastewater by sinusoidal alternating current coagulation: response surface methodology and removal mechanism.

A novel sinusoidal alternating current coagulation (SACC) technique was used to remove the Zn2+ from wastewater in the present study. The response surface methodology was used to analyze the effect of current density, time, initial pH and initial Zn2+ concentration in order to obtain the optimum removal efficiency and to lower energy consumption. The results show that SACC with a current density of 0.31 A·m-2 applied to treat wastewater containing 120 mg·dm-3 Zn2+ at pH = 9 for 21.3 min can achieve a removal efficiency of Zn2+ of 98.80%, and the energy consumption is 1.147 kWh·m-3. The main component of flocs produced in SACC process is Fe5O7OH·4H2O (HFO). Large specific surface area and good adsorption performance of HFO are demonstrated. There is strong interaction between Zn2+ and HFO. Zn2+ is adsorbed and trapped by HFO and then co-precipitated. Freundlich adsorption isotherm model and pseudo-second order kinetics model explained the Zn2+ adsorption behavior well. The Zn2+ adsorption on HFO is an endothermic and spontaneous process.

Elemental mercury removal by I−-doped Bi2WO6 with remarkable visible-light-driven photocatalytic oxidation

In this work, I–-doped Bi2WO6 composites were synthesized using a one-step hydrothermal method, and the effect of iodine doping on their photocatalytic efficiency in gas-phase elemental mercury removal was evaluated under visible-light irradiation. The results showed that 1.0 wt.% iodine doped Bi2WO6 exhibited the optimal Hg0 removal efficiency of 87.6 % and 97.5 % under N2+O2+CO2 and N2+O2+CO2+SO2+NO conditions, respectively. The improved photocatalytic activity of Bi2WO6 can be ascribed to the reduction in the potential energy of its conduction band and recombination rate of electron-hole pairs, as well as the acceleration of charge transfer. The density functional theory calculations showed that iodine was doped in the (WO4)2– layer and oxidized HgO can be adsorbed on the surface of I– doped Bi2WO6. The OBi site was found to be exhibit weak adsorption with respect to HgO, implying that most conducive to the desorption of HgO. Finally, the photocatalysis mechanisms was elaborated.

Catalytic performance improvement of volatile organic compounds oxidation over MnO and GdMnO3 composite oxides from spent lithium-ion batteries: Effect of acid treatment

In this work, cathode materials of spent lithium-ion ternary batteries are recovered and used as metal precursor to prepare multi-metal oxides MnO x (SY) and GdMnO 3 (SY) via combustion method and sol–gel method, respectively. Furthermore, a series of MnO x (SY)-n and GdMnO 3 (SY)- n ( n = 0.05, 0.10, 1.00, 4.00, n represents the dilute HNO 3 concentration) catalysts are fabricated by acid treatment of MnO x (SY) and GdMnO 3 (SY) samples and catalytic activities of oxygenated VOCs oxidation over all the prepared catalysts are investigated. Catalytic evaluation results show that acid-treated MnO x (SY)-0.10 and GdMnO 3 (SY)-0.05 samples perform the optimum VOCs removal efficiency respectively, which may be attributed to their obvious enhancement of physicochemical properties. In detail, MnO x (SY)-0.10 and GdMnO 3 (SY)-0.05 samples exhibit the larger specific surface area, bigger amount of surface high-valence metal ions (Mn 4+ , Co 3+ , Ni 3+ ), more abundant adsorbed oxygen species and better low-temperature reducibility, which can play a crucial role in the significant improvement of VOCs oxidation. In situ DRIFTS results imply that the possible main intermediates are -OCO, -COO and -C-O species produced during VOCs oxidation. Possible by-products are further determined via TD/GC–MS analysis.

Characterization and Mechanisms of a New Carbonaceous Adsorbent Based on Black Liquor Loaded with Iron Oxide for Removal of Tripolyphosphate Ions

The impregnation process has successfully prepared a novel composite of iron oxide/carbon from black liquor (CA-BL/Fe) as an adsorbent for the removal of tripolyphosphate ions. Black liquor is a secondary product of the bioethanol pre-treatment process. X-ray diffraction results showed that the main iron oxide species present in the CA-BL/Fe was goethite (α-FeOOH). Interestingly, the specific surface area of CA-BL/Fe was 504 m2/g higher than that of commercial activated carbon of 356 m2/g. The adsorption performance showed that tripolyphosphate ion removal efficiency increased by increasing the adsorbent dosage, pH, and contact time. At the same time, it decreased with an increase in the initial concentration of tripolyphosphate. By controlling the environment pH value, the optimum removal efficiency of tripolyphosphate ions with CA-BL/Fe was 96.87%, with the adsorption capacity of 1.5922 mg/g for 1 h measurement. In this study, the dominant mechanisms of tripolyphosphate adsorption are electrostatic attraction and ion exchange. The result of this study is expected to be the basis for further promising adsorbent material for tripolyphosphate ion.

Ultrasound-assisted cleaning chloride from wastewater using Friedel’s salt precipitation

The chloride salt derived from the rare earth smelting wastewater was effectively dislodged using Friedel’s salt precipitation assisted with ultrasonic enhancement. Various single factors such as the reagent ratio, temperatures, reaction time and agitation speed were determined and investigated systematically. Results showed that the optimal single-stage removal efficiency were 88.22% and 80.89% with and without ultrasonic strengthen, respectively. The particle size distribution, morphology and elemental analysis of the precipitation were carried out by TEM, SEM, EDS and XRD analysis. These results revealed that the effect of ultrasonic has been given prominence to the removal efficiency of chloride salt. It is attributed to the cavitation and mechanical disturbance effect of ultrasound. In order to further decline the chloride, a two-stage de-chlorination carried out, the result indicated that the concentration of chloride was 120 mg/L and 430 mg/L with and without ultrasonic strengthening afterwards two-stage de-chlorination, respectively. The chloride concentration can fully meet the effluent concentration requirement under the effect of ultrasonic enhancement.

Response surface modelling of the biosorption of Zn(II) and Pb(II) onto Micropogonias undulatus scales: Box\u2013Behnken experimental approach

In this study, the scales of Micropogonias undulatus fish were investigated as precursors for the development of low-cost biosorbent for the removal of Pb(II) and Zn(II) from aqueous media.The biosorbent was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffractometry (XRD). Adsorption parameters (temperature, biosorbent dosage and contact time) were optimised using response surface methodology Box–Behnken experimental design. The optimal factors for Zn(II) removal by croaker fish scale were 145.5 min, 7.01 g/L biosorbent dosage, 30 °C and pH 5.4. The optimal factors for the removal of Pb(II) were 179.3 min, 6.61 g/L biosorbent dosage, 20 °C and pH 3.4. The numerical optimisation revealed that the optimal removal efficiency for Zn(II) and Pb(II) sorption is 96.45% and 98.76%, respectively. The biosorption of both heavy metals was best fit to Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamics studies revealed that the biosorption process was exothermic and spontaneous.

Ammonia and COD Removal From Landfill Leachate Using MAP Precipitation Method

<p>Most of the major cities in our country are opposed to the problem of water pollution due to the uncontrolled leachate resulting from the decomposition of solid wastes in irregular landfills. The waste waters that have high nitrogen content such as leachate cause various problems like eutrophication. In this study; the preliminary treatment of leachate which formed on the landfill site storing solid wastes of Samsun Metropolitan Municipality by MAP (Magnesium ammonium phosphate) precipitation was examined. For this purpose, optimization of the parameters that affecting the MAP precipitation was performed and the conditions for optimum removal efficiency were investigated. As a result of MAP precipitation, various mole ratios were tested with the aim of providing the best ammonia removal efficiency. The maximum ammonia removal was found to be 90.63% at pH 9.5 and at Mg:NH4:PO4 ratio of 4: 1: 2.2. At this conditions the ammonia concentration was decreased from 1792 mg/L to 168 mg/L. Experimental data were also evaluated and the regression equations of ammonia and COD removal were obtained using Minitab 16 statistical software.</p>

Study on the influencing factors of removal of NOX from cement kiln flue gas by sewage sludge as a denitration agent

Experimental study on the influencing factors of using sewage sludge as a denitration agent for cement industry was carried out on a self-made laboratory-scale fluid-bed reactor. Results indicate that sludge combustion at 900°C shows an ideal NOX (the sum of NO and NO2) removal activity under simulated working conditions of cement precalciner. The optimal removal efficiency of NOX can reach 70.36 ± 3.59% in the presence of cement raw meal (CRM) at a sludge particle size range of 0.18-0.25mm and the sludge dosage of 0.75g/min. Besides, the NOX removal efficiency increases to 76.94 ± 5.02% in the absence of CRM, indicating that cement raw meal inhibits the NOX removal. This phenomenon may be attributed to the fact that CRM has promotion effect on NH3 produced and obvious inhibitory effect on CO produced; while NH3 and CO play a leading role in NOX reduction, the combined effect leads to the decrease of NOX removal. Moreover, the relationship between the composition of CRM on the inhibition of NOX removal is MgO < CaCO3 < CRM < Al2O3 <Fe2O3. Meanwhile, the effect of additive variety on the sludge denitration activity indicates that urea significantly promotes the NOX removal, which is attributed to the decomposition of urea to form NH3. The stability experiment shows that sludge denitration efficiency remains stable above 70% in the presence of CRM and can reach over 80% when adding appropriate urea. This method can realize the removal of NOX in the cement kiln flue gas and the resource utilization of sludge. It is a promising method for sludge disposal.

Continuous electrocoagulation degradation of oily wastewater with Fe78Si9B13 amorphous ribbons.

The oily wastewater was treated by electrocoagulation with Fe78Si9B13 amorphous ribbons as anode and graphite plates as cathode under such processing parameters as different pH values and current density, respectively. The degradation effect on the oily wastewater was characterized by chemical demand oxygen (COD), while the ribbons before and after using were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that under the conditions of pH = 3 and current density being 3.125A/cm2, the optimal COD removal efficiency was obtained to be 73.22%. Compared with the ordinary crystalline iron plate, the COD removal efficiency of resultant wastewater degraded by the amorphous ribbons is more than doubled. Simultaneously, the Fe78Si9B13 amorphous ribbons exhibit good structural stability even after four cycles of using.

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), 1H nuclear magnetic resonance spectrometer (1H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8–12 mg/L, G value of 100–250 s − 1, and pH value of 4–8. The optimal dosage of PAFC is 90–150 mg/L with a pH of 2–12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90–150 mg/L, P(DAC-MAPTAC-AM) dosage of 8–12 mg/L, and pH range of 2–6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.

Assessment of a submerged membrane bioreactor with composite ceramic filters for cassava wastewater treatment

Cassava processing activity is characterised by the generation of an enormous quantity of toxic wastewater with detrimental effects on the environment if disposed of without adequate treatment. To alleviate this concern, lab-scaled cylindrical-shaped composite ceramic filters produced from rice husk and clay mixed with equal proportions of activated carbon, kaolin and sherd powder were produced and assessed in a membrane bioreactor. The permeate obtained from the filter with 2.39% rice husks, 0.95% activated carbon, 0.80% kaolin, 0.40% sherd powder and 95.47% clay gave the optimum pollutant removal efficiency. The average removal efficiencies of the chemical oxygen demand (COD), biochemical oxygen demand (BOD), turbidity and hydrogen cyanide (HCN) were 98.32, 78.93, 37.81 and 56.52%, respectively. The pH increased from 3.8 to a maximum value of 6.5. The flux ranges from 0.005 [m&lt;sup&gt;3&lt;/sup&gt;·(m&lt;sup&gt;2&lt;/sup&gt;·d&lt;sup&gt;–1&lt;/sup&gt;)] to a maximum value of 0.108 [m&lt;sup&gt;3&lt;/sup&gt;·(m&lt;sup&gt;2&lt;/sup&gt;·d&lt;sup&gt;–1&lt;/sup&gt;)] obtained for the filter with 1.45% rice husks. The availability of low-cost construction materials and the ease of operation makes the concept a promising option for treating cassava wastewater, however, an optimisation study is required to improve the filter performance and enhance the field applications.

Dye degradation and kinetics of online Electro-Fenton system with thermally activated carbon fiber cathodes

Abstract In this study, the effect of the gas type (N2 or CO2) and activation time (0−10 h) on the thermal activation of carbon fiber (CF) electrodes being used as the working electrodes was tested in an Electro-Fenton (EF) system with Pt anodes; this was aimed at achieving the total organic carbon (TOC) removal for the Acid Orange 7 (AO7) dye. An EF experimental system was established to perform online analyses that were different from the majority of those in the literature. Furthermore, to test the effectiveness of the EF process parameters, the cathodic potential (0.5–2.5 V) and Fe2+ concentration (0.2−1 mM) were investigated. The initial solution dye concentration (0.1 mM), pH (3), and electrolyte concentration (50 mM) were held constant in this study. In an undivided glass reactor, dry air was supplied (16 L/h) to the system in batch mode, and a 600-ml dye solution was added. The optimum dye and TOC removal efficiencies at 0.8 V with 0.3 mM of Fe2+ by using CF activated at 900 °C under N2 for 5 h were 92.9 % at 15 min and 84.0 % at 120 min. In contrast, a kinetic analysis was performed using data from an online analysis system. Accordingly, the kinetic study of the degradation reaction was evaluated in two stages, namely, for the first 3.2 min and for the subsequnet time frame. In addition, the CF electrode was found to be a promising electrode for electro-oxidation systems, with augmentaions in the electroactive surface area and crystallite size by 46.64 % and 17.15 %, respectively.

Achieving single-stage autotrophic nitrogen removal by composite membrane aerated biofilm with gel under two microbial entrapping patterns: experimental and modeling aspects.

Single-stage autotrophic nitrogen removal offers advantages of low energy and carbon consumptions. Based on previous work about a novel composite membrane aerated biofilm (CMAB), two microbial entrapping patterns (mixed and stratified patterns) were evaluated for their applicability to artificially regulate the spatial distribution of distinct microbial aggregates for single-stage autotrophic nitrogen removal. Experimental results showed that the stratified pattern caused little accumulation of NO2- and NO3-, which leads to a superior nitrogen removal performance compared with the mixed pattern. Candidatus Kuenenia was found to be the major anammox bacterium in the gel film of the mixed pattern and the outer film of the stratified pattern. In contrast, Nitrosomonas, as a representative genus of ammonia-oxidizing bacteria, was substantially enriched in the inner film of the stratified pattern and the gel film of the mixed pattern. Finally, modeling results further confirmed the advantages of the stratified pattern with respect to the formation of rational microbial and nutrient profiles in gel films. The ratio of partial nitrification and anammox film thicknesses should remain below 3:2 to obtain a high fraction of anammox bacteria and to avoid NO2- accumulation. Increasing O2 surface loading does not affect microbial profiles, but can greatly promote the TN removal performance only in the stratified pattern. Overall, the stratified pattern should be employed to achieve optimal microbial profiles and nitrogen removal efficiency.

Fabrication of efficient CuO / graphitic carbon nitride based heterogeneous photo-Fenton like catalyst for degradation of 2, 4 dimethyl phenol

Considering the drawbacks of iron-based Fenton process, this work was aimed at designing of an efficient photo-Fenton like process via coupling of CuO/g-C3N4 photocatalyst with H2O2. The photo-Fenton like catalytic process was used for degradation of 2, 4-dimethyl phenol (DMP). The X% CuO/g-C3N4 Z-shceme photocatalyst samples were fabricated by thermal calcination method, varing the CuO percentage (X = 2 %, 4 % and 8 %) loaded on g-C3N4. A lab-scale photoreactor was used to assess and select the optimal removal efficiency for DMP degradation. The photocatalyst was characterized by advanced spectral techniques. Coupling of CuO/GCN system with H2O2 significantly improved photocatalytic activity via photo-Fenton process. The kinetics of photo-degradation was found to exhibit pseudo-first order reaction rules. The rate of photodegradation was strongly influenced by pH and different concentrations of H2O2. 4%CuO/g-C3N4/H2O2 system proved to be the most efficient and exhibited much higher photo removal efficiency than CuO/g-C3N4 system and permitted attaining 99 % degradation of DMP in reaction time of 120 min. The successful implementation of this work was effective and of significance for the economical decomposition process of pollutants present in water under visible light irradiation. Overall, utilization of the studied system leads to high catalytic efficiency in a relatively short degradation period, which is of immense potential in water purification.

Comparison of Cr(VI) removal by direct and pulse current electrocoagulation: Implications for energy consumption optimization, sludge reduction and floc magnetism

Conventional direct current electrocoagulation (DC-EC) suffers from issues of plate passivation, large energy consumption and sludge weight, which greatly restrict its application to wastewater treatment with Cr(VI). In this study, positive single pulse current electrocoagulation (PSPC-EC) and alternating pulse current electrocoagulation (APC-EC) were used to solve the above problems. The optimum removal efficiencies of Cr(VI) obtained by DC-EC, PSPC-EC and APC-EC were all over 99 %. The energy consumptions of DC-EC, PSPC-EC and APC-EC were 3.8 × 10−3, 4.0 × 10−4 and 7.6 × 10−4 kWh/mgCr(VI) and the amounts of dry sludge produced were 1.8612, 1.3024 and 1.1246 g/L, respectively. Among the three types of EC, PSPC-EC consumed the least electrical energy and APC-EC produced the least amount of sludge, indicating their advantages over DC-EC. The flocs produced by PSPC-EC had a better spread performance than those of DC-EC and APC-EC, which contributed to a larger surface area for adsorbing Cr(VI). It should be noted that EC may generate magnetic flocs with easily available iron electrode. Our findings indicate it is possible to adjust the magnetic strength of the flocs simply by adjusting the pulse current on electrode, which has not been reported in previous studies. This exhibits the potential to avoid adding complicated synthetic magnetic coagulants in the water treatment construction and cut down chemical operation cost. Also, it enlightens those dedicated to electrochemistry to develop magnetic-floc-generating electrodes for enhancing contaminant separation and water purification.

Removal of disperse and reactive dyes from aqueous solutions using ultrasound-assisted electrocoagulation

This study investigates the effectivenesses of electrocoagulation, ultrasound, and ultrasound-assisted electrocoagulation processes for the removal of color and chemical oxygen demand (COD) from aqueous dye solutions. The coupling of electrocoagulation processes with ultrasound has been found useful for water and wastewater treatment in recent years. These experimental results demonstrate that ultrasound-assisted electrocoagulation processes provide greater color and COD removal than ultrasound or electrocoagulation processes alone. The optimum conditions for the combined process were found to be Fe-Fe-SS-SS/Al-Al-SS-SS (electrode connection type) in the monopolar electrode connection mode; 75 and 50 A m−2 (current density) for RR241 and DB 60, respectively, at a fixed frequency of 40 kHz; and an ultrasound power of 180 W in a 1 L aqueous solution. Under these optimum conditions, the color and COD removal efficiencies for an aqueous solution of 100 mg L−1 reached 99–99.9% and 100 - 100% for RR241 and DB 60, respectively. Complete removal was achieved for both COD and color by employing a combination of ultrasound-assisted electrocoagulation (US + EC) with only 4 min of electrolysis, while the traditional EC treatment achieved removal of approximately 87% of COD and 92% color for both dyes using the MP-P connection mode for 5 min. Conversely, ultrasound power alone removed approximately 34–60% of color and 30–36% of COD for RR241 and DB 60, respectively. Compared with the traditional EC treatment, the combination of ultrasound irradiation and electrocoagulation treatment significantly reduced electrode passivation and increased the removal of pollutants in shorter operation times.

Enhanced aqueous phase arsenic removal by a biochar based iron nanocomposite

Zerovalent iron nanoparticles (nZVI) were initially prepared via reduction of ferric chloride (FeCl3) using sodium borohydride (NaBH4) and then precipitated onto a biochar prepared from the pods of Cassia fistula via pyrolysis. The biochar based iron nanocomposite (nZVI-BC) so fabricated was then fully characterized and a series of adsorptive experiments performed in aqueous solution to optimize the removal efficiency of two inorganic As species (As(III) and As(V)) over a range of operating parameters including adsorbent dose, contact time, initial As concentration, pH, stirring rate and temperature. Batch adsorption isotherms best fit the Langmuir adsorption model (r2 > 0.96 for As(III) and r2 > 0.98 for As(V)), yielding maximum adsorption capacities of 1.04 and 1.40 mg g−1 for As(III) and As(V), respectively with residual As concentrations well below the WHO prescribed limit of 10 μg L−1 for drinking water. Optimum removal efficiencies of 99.1% for As(III) and 96.1% for As(V) were achieved at initial As concentration of 1.00 and 1.25 mg L−1, respectively. The mechanism of As removal involved a combination of surface specific electrostatic, H-bonding and redox reactions, where redox reactions eliminated formation of highly toxic As(III) in favor of As(0) and As (V). Using the optimized conditions nZVI-BC was employed to remove 91.5–93.2% of As from a real As laden groundwater collected from the Sahibganj district in Jharkhand, India. Overall, the nanocomposite showed great promise as a cost-effective material for quickly adsorbing As from aqueous solution and could thus potentially be used for remediating As contaminated ground water in any part of the world.

Effects of carbon sources on the removal of ammonium, nitrite and nitrate nitrogen by the red yeast Sporidiobolus pararoseus Y1

Heterotrophic nitrification and aerobic denitrification (HN-AD), which is primarily performed by bacteria rather than fungi, is an attractive approach for nitrogen removal. In this study, a red yeast, Sporidiobolus pararoseus Y1, was isolated and shown to exhibit optimal growth and nitrogen removal efficiency on glucose, followed by citrate, sucrose, acetate and starch. The nitrogen removal efficiency increased with increasing initial concentrations of NH4+-N, NO2−-N and NO3−-N from 14 to 140 mg·L-1. At an initial nitrogen concentration of 140 mg·L-1, the maximum removal efficiencies of NH4+-N, NO2−-N and NO3−-N were 98.67%, 97.13% and 83.51% after 72 h incubation, while those of corresponding total nitrogen were 88.89%, 81.31% and 70.18%, respectively. The nitrification (amoA) and denitrification genes (nirK and napA) were amplified from Y1. These results suggest that yeast are also capable of HN-AD, which can be used to remove nitrogen in wastewater systems.