Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

Mixed phase Fe2O3/Mn3O4 magnetic nanocomposite for enhanced adsorption of methyl orange dye: Neural network modeling and response surface methodology optimization

In this research, a novel magnetic mesoporous adsorbent with mixed phase of Fe₂O₃/Mn₃O₄ nanocomposite was prepared by a facile precipitating method and characterized extensively. The prepared nanocomposite was used as adsorbent for toxic methyl orange (MO) dye removal from aqua matrix considering its high surface area (178.27 m²/g) with high saturation magnetization (23.07 emu/g). Maximum dye adsorption occurs at solution pH 2.0 and the electrostatic attraction between anionic form of MO dye molecules and the positively charged nanocomposite surface is the main driving force behind this adsorption. Response surface methodology (RSM) was used for optimizing the process variables and maximum MO removal of 97.67% is obtained at optimum experimental condition with contact time, adsorbent dose and initial MO dye concentration of 45 min, 0.87 g/l and 116 mg/l, respectively. Artificial neural network (ANN) model with optimum topology of 3–5–1 was developed for predicting the MO removal (%), which has shown higher predictive ability than RSM model. Maximum adsorption capacity of this nanocomposite was found to be 322.58 mg/g from Langmuir isotherm model. Kinetic studies reveal the applicability of second‐order kinetic model with contribution of intra‐particle diffusion in this process.     

Polyethyleneimine-grafted polyphosphazene microspheres for rapid and efficient capture of anionic dyes from wastewater

Developing novel adsorbent to capture organic contaminants from wastewater rapidly and efficiently is highly desirable for waste treatment and environmental restoration. Herein, we reported a new amino-rich spherical adsorbent (PZS-PEI) for highly-efficient uptake of anionic dyes from aqueous solution. The PZS-PEI adsorbent was fabricated through a two-step process including synthesis of PZS-Cl microspheres via room temperature polymerization of hexachlorocyclotriphosphazene with bis(4-hydroxyphenyl) sulfone and subsequent surface grafting reaction of PZS-Cl microspheres using branched polyethyleneimine (PEI). The microstructure of as-obtained PZS-PEI microspheres was fully characterized by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, zeta potential, and N₂ adsorption test. The adsorption performance of the PZS-PEI microspheres towards organic dyes was evaluated through carrying out a series of studies including various influence factor analysis, adsorption isotherm, kinetics, and thermodynamics. Results show that the PZS-PEI adsorbent owned good adsorption selectivity towards anionic dyes, and the maximum adsorption capacities for methyl orange (MO), acid chrome blue K, eosin-Y reached 190.29, 152.90, and 92.34 mg/g at 25 °C, respectively. In addition, the uptake behavior of organic dye by the PZS-PEI adsorbent conformed to Freundlich isotherm and pseudo-second order kinetic model, and the adsorption process followed a three-stage intraparticle diffusion mode with an endothermic and spontaneous characteristic. Electrostatic interaction and hydrogen bonding were responsible for the highly-efficient adsorption of the PZS-PEI adsorbent towards typical anionic dye MO.     

Experimental and theoretical studies on protecting steel against 0.5 M H2SO4 corrosion by new schiff base

In this study, a novel green corrosion inhibitor called 2,2'-((1Z,1′Z)-((piperazine-1,4-diylbis(2,1-phenylene))bis(methanylylidene))bis(azanylylidene)) (PMA) has been tested against corrosion of carbon steel in 0.5 M H₂SO₄. Quantum and electrochemical methods were used to evaluate PMA's ability to inhibit the deterioration of carbon steel in an acidic environment. The results revealed that PMA acted as a mixed inhibitor, primarily anodic, whose inhibition action was enhanced by increasing its concentration. At 298.15 K, the maximum efficiency was around 91% with 1 × 10^?3 M PMA in 0.5 M H₂SO₄. The results showed that the inhibition occurred due to adsorption of the PMA molecules on the surface. The adsorbed layer of PMA satisfied the Langmuir adsorption isotherm. The morphology of the surface was examined using scanning electron microscopy.     

Preparation,characterization, biological activity,density functional theory calculations and molecular docking of chelates of diazo ligand derived from m‐phenylenediamine and p‐chlorophenol

A novel azo dye ligand, 2,2′‐(1,3‐phenylenebis(diazene‐2,1‐diyl))bis(4‐chlorophenol), was synthesized from the diazotization of m ‐phenelyenediamine and coupling with p ‐chlorophenol in alkaline medium. Mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the azo ligand (H₂L) were prepared and characterized using elemental analyses, infrared spectroscopy, electron spin resonance, magnetic susceptibility, conductance measurements and thermal analyses. The UV–visible, ¹H NMR and mass spectra of the ligand and its chelates were also recorded. The analytical data showed that the metal‐to‐ligand ratio in the mononuclear azo complexes was 1:1. Diffuse reflectance and magnetic moment measurements revealed the complexes to have octahedral geometry. The infrared spectral data showed that the chelation behaviour of the ligand towards transition metal ions was through phenolic oxygen and azo nitrogen atoms. The electronic spectral results indicated the existence of π → π* (phenyl rings) and n → π* (─N═N) and confirmed the mentioned structure. Molar conductivity revealed the non‐electrolytic nature of all chelates. The presence of water molecules in all complexes was supported by thermal studies. Molecular docking was used to predict the binding between H₂L and the receptors of breast cancer mutant 3hb5‐oxidoreductase, crystal structure of Escherichia coli (3 t88) and crystal structure of Staphylococcus aureus (3q8u). The molecular and electronic structure of H₂L was optimized theoretically and the quantum chemical parameters were calculated. In addition, the effects of the H₂L azo ligand and its complexes on the inhibition of bacterial or fungal growth were evaluated. The prepared complexes had enhanced activity against bacterial or fungal growth compared to the H₂L azo ligand.     

Rapid removal of anionic organic dye from contaminated water using a poly(3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite low-cost adsorbent via adsorption techniques

This research study aims to remove hazardous anionic azo dyes (Congo red (CR)) from aqueous solutions via a simple adsorption method using a poly(3-aminobenzoic acid/graphene oxide/cobalt ferrite) nanocomposite (P3ABA/GO/CoFe₂O₄) as a novel and low-cost nanoadsorbent, as synthesized by a simple and straightforward polymerization method. Typically, 3-aminobenzoic acid (3ABA), as monomer, was chemically polymerized with graphene oxide (GO) and cobalt ferrite (CoFe₂O₄) in an aqueous acidic medium containing an ammonium persulfate initiator. The adsorbent P3ABA/GO/CoFe₂O₄ nanocomposite was characterized using various techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, energy-dispersive analysis by X-ray and Brunauer–Emmett–Teller, vibrating sample magnetometer, and zeta potential techniques. These techniques confirmed the interaction between the poly(3-aminobenzoic acid) with GO and CoFe₂O₄ due to the presence of π-π interactions, hydrogen bonding, and electrostatic forces. Herein, the removal efficiency of dye from aqueous solution by the adsorbent was studied according to several parameters such as the pH of the solution, dye concentration, dosage of adsorbent, contact time, and temperature. The adsorption of the dye was fitted using a Langmuir model (R² between 0.9980 and 0.9995) at different temperatures, and a kinetic model that was pseudo-second order (R² = between 0.9993 and 0.9929) at various initial concentrations of CR dye. In addition, the data revealed that the P3ABA/GO/CoFe₂O₄ nanocomposite exhibited a high adsorption capacity (153.92 mg/g) and removal for CR dye (98 %) at pH 5. Thermodynamic results showed the adsorption process was an endothermic and spontaneous reaction. It was found that, in terms of reusability, the P3ABA/GO/CoFe₂O₄ adsorbent can be used for up to six cycles. In this study, P3ABA/GO/CoFe₂O₄ nanocomposites were found to be low cost, and have an excellent removal capability and fast adsorption rate for CR from wastewater via a simple adsorption method. Moreover, this adsorbent nanocomposite could be simply separated from the resultant solution and recycled.     

Removal of cibacron blue 3G-A (CB) dye from aqueous solution using chemo-physically activated biochar from oil palm empty fruit bunch fiber

A novel biodegradable adsorbent called pyrolysed empty fruit bunch fibres (PEF) was prepared by chemo-physical activation of empty fruit bunch fibres (EFB) biochar for removal of cibacron blue 3G-A (CB) dye from aqueous solution. PEF was characterized using FTIR, SEM-EDX, XRD and BET techniques. The N₂ adsorption-desorption isotherms indicated PEF’s surface area to be 362.84 m²g⁻¹ and XRD attributed amorphous nature to PEF. After adsorption process, PEF has smoother surface morphology, increase in carbon by weight and shift in functional groups. The established adsorption optimum conditions were pH 10, 45 min contact time and 0.10 g/100 mL adsorbent dosage with 99.05% CB dye removal capacity at 343 K and initial dye concentration 100 mg/L. Desorption ratio >90% after seventh cycle of adsorption-desorption experiments confirmed high reusability (regeneration) of PEF. Pseudo second order kinetic and Freundlich were better fitted with kinetic and isotherm model respectively, while mechanism of adsorption was controlled by film diffusion (external mass transfer). Thermodynamic studied revealed ΔG, ΔS and ΔH to be −3.12 MJ/mol K, 9.11 kJ/mol K, 6.83 kJ/mol respectively at 343 K. The negative value of ΔG, positive values of ΔS and ΔH indicated spontaneity, feasibility and endothermic nature of CB dye adsorption from aqueous solution onto PEF.     

Combinatıon of a Box-Behnken design technique with response surface methodology for optimization of the photocatalytic mineralization of C.I. Basic Red 46 dye from aqueous solution

The photodegradation of an industrial azo dye C.I Basic Red 46 was examined in a fixed-bed photoreactor using UV-lamps simulated to the solar irradiation. In our photodecolorization study, the UV/TiO₂ process was optimized using the Box-Behnken approach to evaluate the synergistic effects of three independent parameters (initial concentration of the dye, flow rate, and UV intensity) on mineralization effectiveness. The response surface methodology was in good promise with the prediction model (coefficients of determination of decolorization and mineralization were R²_Dec = 0.997 and R²_TOC = 0.994, respectively). The effects of the factors could be estimated from a second–order polynomial equation and student’s t-test. The optimal parameters of decolorization and mineralization were as follows: initial concentration of colorant 25 mg L⁻¹, rate of fluid flow 0.3 L min⁻¹, and ultraviolet light intensity 38.1 W m⁻². The decolorization and mineralization removal efficiency under these optimal conditions were 100% and 57.63% respectively. These results indicate that optimization using response surface methodology, based on the Box-Behnken approach, is an excellent tool for determining the optimal conditions, and the process can be easily extrapolated for a specific treatment of real waste water containing the azo dye C.I Basic Red 46. Also, the intermediates that were produced during photodegradation process of Basic Red 46 were determined by GC/MS.     

Sustainable fabrication of silver-titania nanocomposites using goji berry (Lycium barbarum L.) fruit extract and their photocatalytic and antibacterial applications

Silver-titania nanocomposites (Ag-TiO₂ NCs) have unique functional attributes due to their photocatalytic and antibacterial properties. In this study, titania nanoparticles (TiO₂-NPs) were successfully in-situ decorated with silver nanoparticles (Ag-NPs) using the aqueous extract of goji berries (Lycium barbarum L.) as a bioreducing and stabilizing agent. Different Ag-TiO₂ NCs were synthesized by treating different concentrations of silver nitrate with a specific concentration of TiO₂-NPs in the presence of fruit extract. The green-synthesized NCs were characterized using several techniques viz., ultraviolet–visible spectrophotometry, X-ray diffractometry (XRD), scanning electron microscopy, field-emission transmission electron microscopy (FE-TEM), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. XRD analysis revealed the formation of face-centered cubic (fcc) crystals, and FE-TEM analysis revealed the embedment of Ag-NPs throughout the surface of TiO₂-NPs. The average size of Ag-NPs on TiO₂-NPs increased from 11.2 ± 3.05 nm to 16.4 ± 4.5 nm with an increase in the concentration of silver ions, and the morphology of Ag-NPs was predominantly quasi-spherical and hexagonal. These NCs exhibited an excellent photocatalytic degradation of an azo dye, methylene blue (MB). The synthesized Ag-TiO₂ NCs (3:1) showed higher photocatalytic degradation efficiency of ∼ 93.4% for MB in 130 min under visible light irradiation. Ag-TiO₂ NC_S also exhibited good antibacterial activities towards Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Therefore, the formation of Ag-NPs on the surface of TiO₂-NPs to form Ag-TiO₂ NCs exhibits eco-friendly photocatalytic degradation of azo dye contaminants as well as antibacterial activity.     

Adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface: A spectroscopic study

The adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface at 30 °C in the dark was investigated. The color reduction was monitored by spectrophotometry at 503 nm. The FTIR and Raman spectra of the Direct Red 23 adsorption as a function of ZnO concentration were registered. From the PM3 semi-empirical calculations of the atomic charge density and dipole moment of the Direct Red 23 molecule, it was demonstrated that the azo dye molecule may be adsorbed onto the ZnO surface through molecule geometry modifications, enhancing the interfacial area causing a variation in the bonding frequencies.     

Effect of sunset yellow dye on morphological,optical, dielectric,thermal and mechanical properties of KDP crystal

Herein, we describe the growth and morphology of well-defined dyed crystals of KH₂PO₄ (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.     

Effective scrap iron particles (SIP) pre-treatment for complete mineralization of benzidine based azo dye effluent

This study proposed that hybrid scrap cast iron particles (SIP)-aerobic biodegradation technology could enhance the biodegradability of toxic wastewater. SIP cleaved the azo linkages of Direct Green1 dye to form benzidine, 4-aminophenol, aniline and 1,2,7-triamino-8-hydroxynapthalene-3,6-disulfonic acid. SIP-mediated dye reduction was effective at wide pH range; however, kinetic analysis revealed fastest pseudo-first order dye reduction rate at acidic pH 3 (k_d = 0.549 min⁻¹) followed by pH 9 (k_d = 0.383 min⁻¹) and pH 7 (k_d = 0.318 min⁻¹). The daughter aromatic amines produced were partially adsorbed onto the SIP surface and maximally at neutral pH. The adsorption process followed pseudo-second order adsorption kinetics and Langmuir isotherm. Benzidine was adsorbed more than 4-aminophenol and aniline. BOD₅ of the SIP-treated effluent increased from 0.93 to 12 mg/L showing improved biodegradability. The daughter amines were rapidly mineralized in the aerobic bioreactor within 6 h. Cost-effective SIP pre-treatment could accelerate mineralization and detoxification of recalcitrant wastewater.     

Benzalkonium chloride/titanium dioxide as an effective corrosion inhibitor for carbon steel in a sulfuric acid solution

In this study, the corrosion performance of carbon steel samples in 0.5 M sulfuric acid by the addition of novel inhibitors, 200 ppm of (25% and 50%) titanium dioxide nanoparticles in benzalkonium chloride, was thoroughly investigated. Gravimetric measurements, cyclic and linear potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and hydrogen collection by water displacement evaluated inhibition performance. Analogously, TiO₂/ILB (50%), TiO₂/ILB (75%), and ILB inhibitors enhanced corrosion protection with over 80% inhibition efficiency in electrochemical tests. In addition, weight loss and hydrogen collection measurements reached comparable results. According to potentiodynamic polarization curves, inhibitors exhibited dual behavior, but cathodic protection was more predominant. Scanning electron microscopy (SEM) was employed to examine the surface morphology before and after immersion using corrosion tests. The correlation between electronic properties and inhibition efficiencies of tilted inhibitors was determined by simple linear regression. Electronic properties were calculated for neutral and protonated forms using a polarizable continuum model by the DFT method at the B3LYP/6-311+G (d, p) level of theory. The active adsorbed sites of HM1-HM3 on the metal surface were determined by analyzing their corresponding electrostatic surface potentials (ESP). Furthermore, molecular dynamics simulations were performed to illustrate the most conceivable adsorption configuration between the inhibitors and metal surfaces.     

Green synthesis of copper oxide nanoparticles CuO NPs from Eucalyptus Globoulus leaf extract: Adsorption and design of experiments

The study is concerned with synthesizing copper oxide nanoparticles with leaf extract Eucalyptus Globoulus. The results of scanning electron microscopy (SEM) and dynamic light scattering (DLS) revealed that the green synthesized copper oxide nanoparticles are spherical and have a mean particle size of 88 nm, with a negative zeta potential of ?16.9 mV. The XRD graph showed the crystalline and monoclinic phases of CuO nanoparticles. The average crystalline size around 85.80 nm was observed by the Debye–Scherrer formula. The adsorption characteristics of the nano-adsorbents were investigated using methyl orange, and the adsorption efficiency at room temperature attained 95 mg/g. Copper oxide nanoparticles (CuO NPs) adsorb methyl orange dye most effectively at pH 4.5 when the dye is applied in quantities of 0.04 g/50 mL. Box–Behnken design (BBD) in response surface methodology (RSM) was used to optimize various process parameters, such as pH solution (X₁: 2 – 11), adsorbing dose (X₂: 0.01 – 0.08 g/L), [MO] dye concentration (X₃: 10 – 80 mg/L). Overall, the adjusted coefficient of determination (R²) value of 0.99 demonstrated that the used model was quite appropriate, and the chosen RSM was effective in optimization the decolorization conditions of MO.     

Charge transfer resistance of nitro substituted dibenzalacetone on mild steel against acid attack

Corrosion of metals is a serious industrial problem due to its impact on economic losses and irresistible structural damage. In this work, dibenzalacetone derivatives 1, 5-bis (2-nitrophenyl)-1, 4- pentadien -3-one (BPDO) are employed as controlling agents on mild steel in 1 M H₂SO₄. The effect of BPDO on reducing corrosion of mild steel was analyzed using electrochemical and non-electrochemical methods. From experimental results, it is proved that the protection efficiency increases with enhance in BPDO concentration and diminishes with enlarge in temperature. BPDO is an effective corrosion inhibitor with a 98.64% inhibition efficiency at only 300 ppm concentration. IE diminishes as exposure time increases due to a decrease in the stability of the adsorbed BPDO on the metal surface. The results of Tafel polarization measurements revealed that BPDO acts as a mixed type inhibitor. In both the polarization and Electrochemical Impedance tests, 308K and 300 ppm of BPDO were used, yielding maximal inhibition efficiencies of 98.41% and 97.57% respectively. Langmuir adsorption isotherm is found to be the most suitable way to explain the adsorption of BPDO on the surface of mild steel. Physisorption is proposed from the values of ΔG_ads. Formation of a protective layer on mild steel surface was affirmed by various spectroscopic studies.     

新型复合电极与偶氮染料分子的氧化降解反应的研究

介绍了具有合成H_2O_2和光催化性能的双功能型复合电极、双功能复合电极是 将TiO_2/C光催化剂负载在具有合成H_2O_2性能的新型载体上形成的。在光反应器 中,复合电极作阴极,钌-钛不溶性电极作阳极,低压汞灯作光源,实现了光化学 氧化与光催化氧化在同一电极/溶液界面上的联合作用。当反应器工作时,复合电 极中的TiO_2/C光催化层表面进行着光催化反应,在载体的三相界面上进行着O_2的 2电子H_2O_2的电化学反应,电流效率达82%（J = 15 mA/cm~2）,为·OH自由基的 生成提供了物质源,而且氧的2电子还原反应电位使其表面的TiO_2获得相对于平带 电位约+0.5 V的阳极偏压,改善了TiO_2的光催化活性。实验结果表明,复合电极 对提高偶氮染料分子活性艳红（K-2BP）的氧化降解速度起了重要作用。实验发现 偶氮染料分子在复合电极表面的吸附量与反应速度密切相关。文中讨论了复合电极 的作用原理及偶氮染料分子的氧化降解过程。     

Shellfish waste-derived mesoporous chitosan for impressive removal of arsenic(V) from aqueous solutions: A combined experimental and computational approach

Novel shellfish waste-derived chitosan (CS) has been developed to adsorb As(V) from simulated wastewater under evaluating adsorption process parameters. The coexistence of some competing ions, like SiO₃^2-, Cl^-, NO₃^– and PO₄^3- as well as the regeneration capacity of the spent adsorbent, was explored. The experimental data were modeled using several kinetics and isotherm models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and highly dependent on pH. The Avrami-fractional-order expression supported data best, while the Liu equation described well isotherm data at pH 5.0. The maximum uptake capability (Liu) was 12.32 mg/g, and the highest removal performance (99 %) was obtained at optimum pH 5.0. Molecular dynamics simulations were performed to more clearly illuminate the atomic-level interactions between arsenic species and CS surface in both acidic and basic mediums. After four adsorption–desorption cycles, CS exhibited more than 90 % As(V) removal efficiency. The results of this study indicates that low cost shellfish derived chitosan is promising for efficient removal of As(V) from water body and can be used to remove other pollutants from watewater.     

Enhanced adsorption performance of a novel Fe‐Mn‐Zr metal oxide nanocomposite adsorbent for anionic dyes from binary dye mix: Response surface optimization and neural network modeling

A novel adsorbent, Fe‐Mn‐Zr metal oxide nanocomposite was synthesized and investigated for removal of methyl orange (MO) and eosin yellow (EY) dyes from binary dye solution. The magnetic nanocomposite has shown surface area of 143.01 m²/g and saturation magnetization of 15.29 emu/g. Optimization was carried out via response surface methodology (RSM) for optimizing process variables, and optimum dye removal of 99.26% and 99.55% were obtained for MO and EY dye, respectively with contact time 62 min, adsorbent dose 0.45 g/l, initial MO concentration 11.0 mg/l, and initial EY concentration 25.0 mg/l. A feed forward back propagation neural network model has shown better prediction ability than RSM model for predicting MO and EY dye removal (%). Adsorption process strictly follows Langmuir isotherm model, and enhanced adsorption capacities of 196.07 and 175.43 mg/g were observed for MO and EY dye, respectively due to synergistic effects of physicochemical properties of trimetal oxides. Surface adsorption and pore diffusions are the mechanisms involved in the adsorption as revealed from kinetic studies.     

Chitosan as a biosorbent for adsorption of iron (II) from fracking wastewater

In this work, porous chitosan (CS) was investigated as a biosorbent for the removal of iron (II) from the synthetic fracking wastewater. The underlying problem with the production water from fracking industries is that it contains iron (II) up to 55 mg/L, which needs to be eliminated. Porous CS had a specific surface area of 1.05 m²/g with the average pore diameter of 319 A, as determined by using Brunauer‐Emmett‐Teller surface area analysis. The kinetics, isotherms, and thermodynamic analysis confirm that the porous CS can be a potential candidate for iron (II) removal. Both the pseudo‐first‐order model and pseudo‐second‐order model have good fit on iron (II) adsorption with the porous CS. Kinetic studies revealed that the CS‐iron (II) adsorption system was controlled by intraparticle diffusion. The monolayer adsorption capacity of the porous CS from Langmuir model was found to be 51.81 mg/g. The experimental data were fitted against common adsorption isotherms and yielded excellent fits in the following order: Langmuir > Temkin > Freundlich > Dubinin‐Radushkevich isotherms. Thermodynamic studies revealed that the adsorption of iron (II) onto porous CS was feasible and spontaneous. The adsorption process is endothermic, and the entropy is the driving force.