Optimum Removal Efficiency Research Articles

Nanophotocatalytic treatment of seawater using TiO2 immobilized and suspension system under solar irradiation

Organic fouling in desalination plants is a crucial phenomenon resulting in the deterioration of nanofiltration/reverse osmosis filtration performance of membranes and salt-rejection characteristics. In this research, the efficiency of TiO2-suspension and TiO2-immobilized photocatalysis to pretreat seawater under natural solar irradiation has been investigated. The solar nanophotocatalytic performance was evaluated in terms of chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency from feed seawater. Modelling and optimization study was performed in TiO2 suspension system to determine the effect and optimum settings of input parameters such as pH of seawater, reaction time, TiO2 dosage, initial TOC of seawater, and airflow rate into the photoreactor. In a full factorial design, the photocatalytic efficiency of TiO2 nano-thin film immobilized on borosilicate glass tubes was assessed in terms of methanol − TiO2 ratio, nitric acid − TiO2 ratio and solar irradiation time. The optimum removal efficiency of TOC and COD removal in the immobilized system was determined as 51.98% and 57.25%, respectively, at the input factor setting: methanol- TiO2 ratio = 15: 1, nitric acid- TiO2 ratio = 6:1 and solar irradiation time = 120 min. The optimum organic degradation in suspension system was found to be: TOC removal = 73.47% and COD removal = 65.48%.

Performance of citrus charcoal and olivepomace charcoal as natural substrates in the treatment of municipal wastewater by vertical flow subsurface constructed wetlands

This research investigated two pilot scale vertical flow constructed wetlands systems (VFCWs) with alternative substrates (olivepomace charcoal and citrus charcoal) for removing inorganic pollutants, organic, and pathogens from municipal wastewater of secondary treatment. Each system design consists of two stages, the first one included olivepomace charcoal, while the second design included olivepomace charcoal with citrus charcoal. The system configurations were optimized and operated under different hydraulic retention time HRT (12-24-36-48-96-144-192 h).The results of tests revealed that the optimal removal efficiency for COD, BOD, TKN and Fecal Coliform obtained in system2 (98%, 98%, 71% and 99% at192 h), respectively. The highest TP and TSS removal was observed in the system1 (80% and 97% at 192 h), respectively. The pollutants (COD, BOD, TKN and Fecal Coliform) adsorption capacity of citrus charcoal is faster than citrus charcoal with olivepomace charcoal. However, olivepomace charcoal achieved better removal efficiency with an increase HRT. Overall, citrus charcoal and olivepomace charcoal proved to be efficient alternative substrates in CWs.

A Facile Fabrication of ZnFe2O4/Sepiolite Composite with Excellent Photocatalytic Performance on the Removal of Tetracycline Hydrochloride.

The excellent photo-response of ZnFe2O4 in the visible light region makes it a promising catalyst, whereas some defects like serious particle agglomeration and easy recombination of photo-generated electron-hole pairs hinder its application. In this work, the ZnFe2O4/sepiolite (ZF-Sep) composites were synthesized using a co-precipitation method. The obtained ZF-Sep composites were characterized by XRD, SEM, TEM, FT-IR, XPS, BET, VSM and DRS. Moreover, the photocatalytic performance was evaluated by the tetracycline hydrochloride removal efficiency under simulated visible light illumination. The results displayed that the ZnFe2O4 with average sizes about 20 nm were highly dispersed on sepiolite nanofibers. All the composites exhibited better photocatalytic performance than pure ZnFe2O4 due to the synergistic effect of the improvement on the agglomeration phenomenon of ZnFe2O4 and the reduction on the recombination rate of photo-generated electrons and holes. The optimum removal efficiency was that of the ZF-Sep-11 composite, which reached 93.6% within 3 h. Besides, the composite exhibited an excellent stability and reusability. Therefore, ZF-Sep composite is a promising catalyst for the treatment of wastewater contained antibiotics.

Improving the quality of stabilization pond effluents using hybrid constructed wetlands

Water shortage and excessive use of water resources in arid and semi-arid regions, such as Iran, highlights the importance of using treated wastewater, especially for the highly demanding agricultural sector. Constructed wetlands (CWs) are among green technologies that offer an efficient and cost-effective wastewater treatment. This study investigates the complementary treatment of effluent from the Fooladshahr wastewater treatment plant, Isfahan, Iran, using pilot-scale CWs with horizontal (H-CW) and horizontal-vertical flow (HV-CW). The performance of two substrates, pumice and gravel, and the effect of using plants (Phragmites australis) was compared. Maximum removal efficiencies of total suspended solids (TSS) and biochemical oxygen demand (BOD5) were observed in the case of unplanted and planted HV-CW with pumice bed, respectively. In the case of gravel bed, planted H-CWs demonstrated maximum chemical oxygen demand (COD) removal efficiency. The highest mean outflow concentrations for TSS, BOD5 and COD were obtained in unplanted H-CW with pumice bed, likely due to shorter retention times compared to HV-CWs, as well as due to the absence of plants providing the required physicochemical and biological conditions for high performance treatment. Phosphate (PO43−) removal efficiency demonstrated seasonal dependency, where the highest values were obtained in warm seasons. In the case of fecal coliforms (FC), no significant differences were observed between the studied HV-CWs during the whole study period. Based on our results, planted H-CW with gravel bed provided an optimum removal efficiency while requiring a smaller footprint and lower expenditure than HV-CWs. This study demonstrates the application of CWs as an affordable solution for treating domestic wastewater for various reuse application in developing countries with water crisis, such as Iran.

Fabrication of Z-scheme VO-Bi2WO6/g-C3N4 heterojunction composite with visible-light-driven photocatalytic performance for elemental mercury removal

Photocatalytic Hg0 oxidation under visible light radiation is an economic and feasible approach to deal with energy and pollution problems. In this paper, the photocatalytic oxidation capability of gaseous elemental mercury by Bi2WO6 under visible light radiation was further improved by introducing oxygen vacancies and forming the Z-scheme heterojunction with g-C3N4. Firstly, the experimental results demonstrate that oxygen vacancies were beneficial to reduce the band gap, with nearly trebling increase in mercury removal efficiency than that before modification (6.5%) under visible light. Secondly, the Vo-Bi2WO6/g-C3N4 composite with 10 wt% g-C3N4 content exhibited an optimal Hg0 removal efficiency of 87.2% compared with Vo-Bi2WO6 (17.8%) and pure g-C3N4 (12.4%) under the N2 + 4%O2 atmosphere. The improved photocatalytic efficiency could be primarily due to the formation of a built-in electric field between g-C3N4 and Vo-Bi2WO6 through the carrier transmission mechanism of Z-scheme heterojunction, enhancing the light absorption intensity in the visible range, facilitating the movement and separation of photoinduced carriers as well as improving the interfacial charge-transfer efficiency. Finally, DFT calculations provides a theoretical basis for the role of oxygen vacancies and the internal electric field generated between two interfaces.

Use of response surface methodology for optimization of fluoride removal efficiency by adsorption on black mustard husk ash

Fluoride removal techniques have been studied for several years. In recent years various fluoride removal techniques have been developed in order to curb the health hazards from fluoride. Adsorption is the most widely used and researched method due to its advantages like economy, highly efficient, simplicity of application etc., over all other available defluoridation methods. This paper deals with the study of adsorption of fluoride using black mustard husk ash as an adsorbing material. The process parameters like pH, adsorbent dose, contact time and stirring rate were optimized using a three- level, four-factor, Box–Behnken design. The regression analysis of the experimental data acquired from 27 runs aided to develop a second order mathematical model in order to predict the fluoride removal efficiency. Using the response optimization, the optimum fluoride removal efficiency was found to be around 87%. The surface response graphs for the different process parameters were plotted and analyzed for studying their effect on adsorption phenomenon. The p-value obtained from the Analysis of Variance model suggested that the model was significant (p-value less than 0.005). The optimum values of pH, contact time, stirring rate and adsorbent dose were found to be 5, 75 min, 200 rpm and 2 g respectively. The predicted and adjusted R2 values were found to be 0.9177 and 0.9264 respectively. Adsorption models like Freundlich and Langmuir were used to validate the results. Langmuir model was seen best fiiting with the results having a R2 value equal to 0.9029. Pseudo first order kinetics and pseudo second order kinetic modelling was studied. The kinetic models showed the influence of physisorption as well as some amount of chemisorption in the adsorption process. From the results obtained it was concluded that the black mustard husk can be efficiently utilized for adsorption of fluoride from water.

Simultaneous carbon and nitrogen removal by anaerobic ammonium oxidation and denitrification under different operating strategies.

Real domestic wastewater was treated initially in a sequencing batch reactor (SBR), with partial nitrification achieved before the effluent was used as the influent for an anaerobic ammonium oxidation (anammox) reactor (ASBR) system. The effects of three factors, hydraulic retention time (HRT), substrate (NO2-/NH4+) ratio, and the ratio of COD to NH4+ (C/N), on the removal of carbon and nitrogen by an anammox and denitrification process were investigated in the ASBR reactor at 24°C. The response surface methodology was used to explore the interactions of the three factors. The results indicated that the nitrogen and carbon removal efficiency was optimum when HRT, substrate ratio, and C/N ratio were 33 h, 1.4-1.6, and 3-5, respectively. The optimal removal rates of NH4+, NO2-, and COD were 96.30%, 97.79%, and 72.91%, respectively. The ΔNO2-/ΔNH4+ and ΔNO3-/ΔNH4+ ratios of the first two conditions were less than the theoretical anammox values of 1.32 and 0.26 due to heterotrophic denitrification. The optimum nitrogen and carbon removal efficiencies of the third condition could be realized by the synergistic effect of denitrification and the anammox process. Analysis of variance (ANOVA) results showed that when the HRT was 33.48 h, the substrate ratio was 1.46, and the C/N ratio was 4.28, the total nitrogen removal rate (TNR) was optimum (90.12 ± 0.1%), verified by parallel experiments.

Concurrent removal of hardness and fluoride in water by monopolar electrocoagulation

Water treatment based on electrocoagulation (EC) is attractive since required chemicals and colloids are produced in-situ. However, optimisation of EC operation parameters is necessary to enhance its efficiency. We optimised EC cell parameters by the response surface method (RSM). The optimal removal efficiencies of hardness (63%) and fluoride (97%) were achieved at 1.98 kW h/m3. With the removal of divalent cations, some anionic species concurrently remove via an energetically feasible route to adjust the charge balance. When simulated water is used (450 mg/L TDS, 580 mg/L CaCO3, 10 mg/L fluorides and pH 6.50), 83% hardness and 99% fluoride are removed with 0.69 kW h/m2 energy consumption. The chemical species in the solution matrix, particularly SO42, significantly affect the hardness and fluoride removal efficiencies. The contaminated EC sludge resulted from feed water is characterised by spectroscopic methods to probe hardness and fluoride removal mechanisms. In the presence of Mg2+, F- interacts with Al-sludge sites forming≡MgF−OH. When Ca2+ and F- are present, both ≡CaF−OH and ≡CaF are formed. In Ca2+, Mg2+ and F- treated Al-sludge dominates CaF−OH and ≡CaF over ≡MgF−OH.

Development of aerobic granulation system for simultaneous removal of C, N, and P in sequencing batch airlift reactor

Conventional biological nutrient removal techniques often have disadvantages like low removal efficiencies, requirement of large footprint, and excess sludge production. Ever increasing stringent discharge standards demand for alternative technologies. In this context aerobic granular sludge (AGS) has evolved as a promising technology for complete nutrient removal. However, degradation of structural integrity of aerobic granules in long run is a prime concern of this technology. This work attempts to develop stable aerobic granules in an automated sequential batch airlift reactor (SBAR) for simultaneous C, N, and P removals under alternating aerobic and anoxic conditions. The reactor was operated at high sludge retention time (SRT). Combined operating strategies of varying dissolved oxygen (DO) concentration and feed cycle times were followed to optimize the conditions for effective granulation and subsequent removal efficiencies. Profiles of extracellular polymeric substances (EPS) and sludge volume index (SVI) were monitored. Optimum removal efficiencies of NH4+-N (92.7%), TN (90.6%), COD (90.1%), and PO43--P (83.2%), and granules of size 1.3–8 mm were achieved in phase IV at operational DO of 1–2 mg/L, and feeding intervals of 15 h and 9 h. NH4+-N (R2 = 0.97, k = 0.5093/h) and PO43--P (R2 = 0.95, k = 0.2574/h) removals were fitted well with first order kinetic model and that of COD (R2 = 0.97, k = 0.0032 L/mg/h) followed second order kinetics. This process is economical as effective biological nutrient and organics removal occurs in a single reactor without requirement of alkalinity supply, and negligible excess sludge production. The process requires small foot print and applicable for decentralized wastewater management in University campuses/tourist resorts/apartment complexes.

Adsorption Isotherm And Kinetic Models For Removal Of Methyl Orange And Remazol Brilliant Blue R By Coconut Shell Activated Carbon

Adsorption technology is one of the efficient and facile method used for wastewater treatment. In this research, coconut shell, an agricultural solid waste was converted into activated carbon via furnace induced and zinc chloride chemical activation techniques. The activated carbon was prepared at activation temperature of 600°C. Anionic dyes, Methyl Orange (MO) and Remazol Brilliant Blue R (RBBR) have been selected due to their harmful effect to the environmental and human. Various effect of parameter such as initial dye concentration, initial pH, adsorbent dosage and agitation speed in batch system were investigated to obtain the optimum condition for both dye adsorption on activated carbon. The optimum dye removal efficiency was around 99% when 5g/L of activated carbon was used. Pseudo-second-order model was the best fitted model with highest correlation compared to other kinetic models. The adsorption behaviour of MO was perfectly presented by the Freundlich model while RBBR was well described by Langmuir model. The maximum adsorption capacity for MO was 59.17mg/g and RBBR was 35.09mg/g. Fourier-transform infrared spectroscopy (FTIR) was utilised to analyse the chemical characteristics of activated carbon before and after adsorption.

Eggshell Utilisation as an Adsorbent for Treatability of Heavy Metals in Paint Wastewater

Abstract : The consumption of eggs to human being and food industry is important as one of the good protein sources in life. Thus abundant of eggshells is produced as daily waste. Objective : This study utilized eggshell as an adsorbent for diminution of heavy metal ions (manganese, zinc and iron) in paint wastewater.Methods : The effects of adsorbent dosage (5 g/l -20 g/l) was studied in batch experiment. The Mn, Fe and Zn concentrations were analyzed in replication using standard method for water and wastewater.Results and Discussion : The adsorbent was able to have more than 50% removal efficiency at 5 g dosage for all the heavy metal. The optimum removal efficiency for the three heavy metal (manganese, iron and zinc) tested occurred at 15 g dosage of the adsorbent (71.2, 96.8 and 85.1%).Conclusions : The study revealed that heavy metals in wastewater from paint industries could be effectively treated with adsorbent produced from eggshell.

Hybrid Methods Combining Computational and Experimental Measurements for the Uptake of Eriochrome Black T Dye Utilising Fish Scales

ABSTRACT The current work describes the removal efficiency of a hazardous azo dye such as Eriochrome Black T from aqueous solution using Sardina fish scales as an inexpensive biosorbent which the characterisation results indicate the presence of hydroxyapatite and collagen fibres. Various parameters that can influence the uptake, like contact time, pH, biosorbent dose were investigated, and the optimal experimental removal efficiency was found at acidic pH. The adsorption behaviour of EBT dye on both collagen and hydroxyapatite (HDA) was highlighted using Metropolis Monte Carlo (MC), radial distribution function (RDF), the density functional theory (DFT), and the electrostatic potential surface (ESP) calculations. The findings result in evidence that the EBT dye presents more capabilityto be adsorbed on the collagen than on the HDA surface mainly in an acidic medium. A good agreement between experimental and theoretical conclusions is obtained. The results illustrated that the experimental data were well followed by the pseudo-second-order kinetic and Freundlich isotherm models. Thermodynamic parameters were determined and show that the biosorption of dye was endothermic.

Process optimization of plasma-catalytic formaldehyde removal using MnOx–Fe2O3 catalysts by response surface methodology

To remove the toxic formaldehyde efficiently, a non-thermal plasma (NTP) system incorporated with MnOx–Fe2O3 catalyst has been developed herein. A response surface methodology (RSM) was utilized to explore the effects of a variety of experimental parameters (gas flow rate, molar ratio of Fe/Mn, and discharge power) on formaldehyde degradation systematically. The results demonstrated that the discharge power has the greatest impact on the formaldehyde degradation process, while the molar ratio of Fe/Mn has the least influence. Moreover, the amount of adsorbed oxygen species, reducibility, and average specific surface area of the tested catalyst are estimated as the dominant factors influencing the catalytic performance. Importantly, the optimal formaldehyde removal efficiency (95.01%) and CO2 selectivity (86.20%) were acquired at 5 W discharge power, 0.5 L min−1 gas flow rate, and 0.71 Fe/Mn molar ratio. This study can thus provide an efficient strategy for formaldehyde removal.

Optimal degradation of Ciprofloxacin in a heterogeneous Fenton-like process using (δ-FeOOH)/MWCNTs nanocomposite

This study was aimed at the synthesis and characterization of ( δ -FeOOH)/MWCNTs nanocomposite as the catalyst for Ciprofloxacin (CIP) removal through a heterogeneous Fenton-like process. The proposed experimental design applies the central composite design (CCD) as a response surface methodology (RSM). The effect of influential parameters, including initial CIP concentration, catalyst dose, H 2 O 2 concentration, initial pH, and reaction time on removal, were investigated. ( δ -FeOOH)/MWCNTs nanocomposite was synthesized using a single-step co-precipitation technique. Besides, nano-feroxyhyte and nanocomposite properties were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), particle size analysis (PSA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM). The inhibitory hale experiment was performed by Escherichia coli (E. coli) to evaluate the antibacterial activity. The optimal CIP removal efficiency (86.9%) was achieved by 131.6 min reaction time, CIP concentration of 10.0 mg/L, catalyst dosage of 23.5 mg, H 2 O 2 concentration of 20.6 mM, and initial pH of 5.3, with a biodegradability index (BOD 5 /COD) of 0.35 Based on the results, ( δ -FeOOH)/MWCNTs showed a significant catalytic activity for CIP removal, which can be attributed to the simultaneous effects of advanced oxidation and absorption.

Radiation synthesis of Fe3O4/SiO2/glycidyl methacrylate/acrylonitrile nanocomposite for adsorption of basic violet 7 dye: Kinetic, isotherm, and thermodynamic study

New functional nanocomposites (Fe3O4/SiO2/GMA/AN) were synthesized by γ‐irradiation copolymerization of glycidyl methacrylate (GMA) and acrylonitrile (AN) of different ratios onto the surface of Fe3O4/SiO2 nanoparticles. The chemical structure and morphology of the nanocomposites were characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The influences of GMA/AN composition ratios (75/25, 50/50, and 25/75 v/v) of nanocomposites on the adsorption of basic violet 7 dye from aqueous solutions was investigated. The Fe3O4/SiO2/GMA/AN nanocomposite with GMA/AN compositions ratio of (25/75 v/v) provides maximum adsorption capacity, and thus it was selected as the suitable ratio for modification by amidoximation reaction. The influences of contact time, pH, temperature, initial concentration, and adsorbent dosage on the adsorption of dye onto Fe3O4/SiO2/GMA/AN‐amidoxime were evaluated. The adsorption capacity of poly (GMA/AN), Fe3O4/SiO2/GMA/AN, and Fe3O4/SiO2/GMA/AN‐amidoxime was 18.7, 114.1, and 181.3 mg/g, respectively. The optimum removal efficiency (90.65%) of dye by Fe3O4/SiO2/GMA/AN‐amidoxime was obtained after 120 min contact time, 200 mg/L dye concentration, and pH 7. The adsorption of dye onto the Fe3O4/SiO2/GMA/AN‐amidoxime follows pseudo‐second‐order adsorption kinetics and fits Langmuir adsorption isotherm, and the adsorption process is endothermic and spontaneous. The prepared Fe3O4/SiO2/GMA/AN‐amidoxime confirmed their possible use as a successful adsorbent for the adsorption of basic violet 7 from wastewater.

Removal of ammonium and phosphate in the simulated wastewater by using coal fly ash adsorbent

The main composition and availability of fly ash cause this waste which has potential as an adsorbent to remove ammonium and phosphate in water. Difference of main composition will cause different removal efficiency. The purposes from this research are to determine optimal condition for removing concentration ammonium and phosphate and to determine the source of fly ash which has great potential for ammonium and phosphate removal in solution. The optimal conditions were carried out by varying pH of solution and adsorbent dosages to remove ammonium and phosphate concentrations in different initial concentrations. Optimum pH of solution in this research is 8 with range of ammonium removal efficiency 8% to 14% and 16% to 75% for removing phosphate which has condition ammonium concentration higher than phosphate. Ammonium concentration lower than phosphate will have a negative effect on the removal. Adsorbent dosage of 4.5 g is able to produce optimal removal efficiency both ammonium and phosphate. From five different sources of fly ash, Punagaya fly ash has the great potential for removal ammonium and phosphate simultaneously which has an adsorption capacity of 7.17 mg/g and 19.50 mg/g for ammonium and phosphate respectively.

Removal of heavy metals from abandoned smelter contaminated soil with poly-phosphonic acid: Two-objective optimization based on washing efficiency and risk assessment

Soil washing is a feasible technology to achieve rapid remediation and reuse of contaminated sites. However, there is still a need to seek eco-friendly and low-cost washing reagents. In this study, a two-objective optimization method has been proposed to investigate the removal efficiencies of eluents and risk of migration (risk assessment code, RAC) of residual metal simultaneously when soil Cd and Pb washed by polyamino polyether methylene phosphonate (PPMP) and bis (hexamethylene triamine penta (methylenephosphonic acid)) (BHMT). The coefficients of determination of the equations proved that D-optimal mixture design could be used for optimizing and modeling of the two objectives during soil washing. And their single-factor (concentration, solution pH, or contact time) and interaction effects indicated that PPMP react with Cd and Pb through chelation at strong acid in soil, whereas acid dissolution effect would convert the stable form of soil Pb into unstable form. BHMT could rapidly remove more acid-soluble fractions of Cd and Pb through the electric double layer adsorption, and is favorable under neutral conditions. Moreover, the optimum removal efficiencies of soil Cd and Pb were 83.98 and 41.29%, and RACs were 45.1 and 5.16% respectively in PPMP washing; accordingly, 69.31 and 28.11% of optimum removals and 32.45 and 0.98% of RACs for soil Cd and Pb were obtained in BHMT leaching. Therefore, PPMP and BHMT are two feasible remediation reagents of the abandoned industrial soils contaminated by heavy metals.

Development of polystyrene coated persulfate slow-release beads for the oxidation of targeted PAHs: Effects of sulfate and chloride ions

In this study, we synthesized polystyrene coated persulfate polyacrylonitrile beads (PC-PSPANBs) to control persulfate (PS) release for targeted PAHs’ degradation in a batch reactor. Initially, the persulfate release rate (ksr = 20.553 h-1) from PSPANBs was fast, but coating the PSPANBs with polystyrene controlled PS release rate (ksr= 2.841 h-1), nearly ten times slower than without coating. When Fe(II) activated PC-PSPANBs applied for 12 h degradation of acenaphthene (ACE), 2-methlynaphthalene (2-MN) and dibenzofuran (DBF), the optimum percent removal efficiencies (% R.Es) were as ACE (82.12%) > DBF (68.57%) > 2-MN (58.80%) and the optimum degradation rate constants (kobs) were found as ACE (11.348 h-1) > 2-MN (3.441 h-1) > DBF (1.101 h-1). The effect of SO42− and Cl− on ACE degradation showed that % R.E and kobs were enhanced with increasing anionic concentrations. The maximum % R.E was achieved for SO42− (76.24%) > Cl− (65.51%), but the highest kobs was in case of Cl− (1.536 h-1) > SO42− (0.510 h-1). The effectiveness of PS release longevity was also found because net degradations of ACE and DBF after first spiking were 12 mg L-1 and 16 mg L-1, while after second spiking were 18 mg L-1 and 10 mg L-1, respectively.

سنتز و بکارگیری نانوکامپوزیت منیزیوم فریت – کیتوسان برای حذف فلوراید از محلول آبی با استفاده از بهینه سازی سطح – پاسخ

Background and objectives: Excess fluoride ions in drinking water cause several diseases so the defluoridation of drinking water with excess fluoride is necessary for human health. Hence this work describes fluoride removal from water using MgFe 2 O 4 – chitosan nanocomposite. Material and methods: In this work a nitrate salt of Mg and Fe were used to synthesis MgFe 2 O 4 through a combustion route. Then MgFe 2 O 4 - chitosan nanocomposite was synthesized using epichlorohydrin as a linker. Characterization of the sorbent was performed with FESEM, TEM, VSM, EDX and XRD techniques. Effective parameters on the adsorption process such as pH, contact time, adsorbent dosage and fluoride concentration was optimized by response surface methodology (RSM) using Box – Behnken design (BBD). Isotherm study was studied at the fluoride concentration range of 10 – 100 mg/L. Results: The optimum value of pH, contact time, adsorbent dosage and fluoride concentration were 2.8, 4.5 min, 19.0 mg and 28.87 mg/L, respectively. At the optimum condition maximum removal efficiency was 98.1%. Results showed that adsorption process followed Langmuir model with capacity of 181.1 mg/g. Conclusion: The result of the present work showed that the nanohybrid has good potential as a cheap magnetic sorbent for environmental remediation purpose as can be used for effective removal of fluoride from water solution.

Application of Zn–Fe layered double hydroxide and its composites with biochar and carbon nanotubes to the adsorption of lead in a batch system: kinetics and isotherms

The adsorption of Pb2+ onto zinc–iron layered double hydroxide (ZnFe–LDH) and its composites coupled with single-walled carbon nanotubes (ZnFe–CNTs) and biochar, which had been obtained from orange peel waste biomass (ZnFe–OPb), was studied in detail. The successful formations of Zn2+- and Fe3+-LDH were investigated by scanning electron microscopy. Moreover, energy-dispersive X-ray spectroscopy revealed that Pb2+ was adsorbed successfully on ZnFe-LDH. Further, both ZnFe-LDH and ZnFe–CNTs exhibited ~ 60% removal efficiencies for Pb2+ at 20 mgL–1 with rapid adsorption at an initial contact time of 30 min, while the equilibrium was achieved at ~ 60 min with a 95% removal efficiency with ZnFe–OPb. Furthermore, the pseudo-second-order kinetics demonstrated the best fit, thus supporting the chemisorption essence of the adsorption mechanism. ZnFe–OPb demonstrated a twofold increase in the adsorption efficiency compared with simple LDH or ZnFe–CNTs, as the initial Pb2+ concentration was enhanced from 10 to 100 mgL–1. The percentage removal and adsorption capacity increased almost linearly as the pH of the solution changed from 2 to 5, suggesting that the optimum pH value was approximately 5 or 6 for all adsorbents. The percentage removal of Pb2+ also increased on increasing the dose. Additionally, the optimum removal efficiency of 99% was obtained with 0.7 g of ZnFe–OPb. The Langmuir model corresponds best with the adsorption data, while the Sips isotherm indicated that ZnFe-LDH exhibited the highest degree of heterogeneity compared with the other adsorbents in this study.