Optimization of Pb(II) biosorption by Robinia tree leaves using statistical design of experiments

Harnessing an amide-based covalent organic framework in solid-phase extraction for chlorophenol analysis in industrial wastewaters

An amide-based covalent organic framework (COF) was successfully synthesized using the reaction between 1,3,5-trimesoyl chloride and ethylenediamine. The structure and morphology of the COF were characterized using Fourier-transform infrared spectra, nuclear magnetic resonance spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area analysis. The COF was employed as a solid-phase extraction adsorbent for the sampling and preconcentration of chlorophenols from industrial wastewater samples prior to high-performance liquid chromatography with ultraviolet detection. The experimental parameters influencing the extraction efficiency including type and volume of eluent solvent, sample solution volume, salt concentration, sample flow rate, and sample solution pH were investigated and optimized using a response surface methodology employing Box-Behnken-design. Under optimized conditions, calibration curves exhibited good linearities over the range of 0.003-10 µg/mL with determination coefficients (R2) ranging from 0.9982 to 0.9999. The method's limits of detection ranged from 0.001 to 0.01 µg/mL. Good repeatability was achieved with relative standard deviations below 4.7%. The developed procedure utilizing the COF adsorbent was successfully applied to determine chlorophenols accurately and precisely in various industrial wastewater samples.

Removal of lead ions using OA-Fe3O4 magnetic nanoparticles-based pickering emulsion liquid membrane: process optimization using box-behnken response surface methodology

The purpose of this study is to explore the pickering emulsion liquid membrane (PELM) performance for removing divalent lead ions (Pb II) from aqueous solution. In the present work, the membrane phase was prepared by dissolving methyltrioctylammonium chloride (Aliquat 336) with Mahua oil and adding oleic acid coated-ferrosoferric oxide (OA-Fe₃O₄) as magnetic nanoparticles. Experimental investigation on percentage removal of lead ions was carried out by studying the influencing process parameters such as pH, agitation speed, stripping concentration, initial feed concentration, surfactant concentration, treat ratio, M/S ratio and carrier concentration. The optimum condition to remove 98.52% of lead ions from the feed solutions has achieved at a stripping phase concentration of 0.3 M, treat ratio of 3, agitation speed of 300 rpm, initial feed concentration of 10 ppm and stabilizer concentration of 2 wt%. The experimental results were validated using box-behnken response surface methodology. The extraction ability of OA-Fe₃O₄ magnetic nanoparticles-based PELM has been evaluated using statistical optimization of all the affecting process factors using the design of the experiments.

Thermodynamic, Nonlinear Kinetic, and Isotherm Studies of Bisphenol A Uptake onto Chemically Activated Carbons Derived from Safou (Dacryodes edulis) Seeds

The interest of this work is to evaluate the possibility of using safou seeds to develop a new low-cost adsorbent and study its application to remove bisphenol A from an aqueous solution for a sustainable and ecological use of this biomass. This was done by optimizing some parameters that influence the adsorption process. The central composite design with four centre points was used to optimize the process variables. The concentration of bisphenol A solution, adsorbent dosage, stirring time, and solution pH on the adsorption capacity were considered, while the response measured was the quantity adsorbed. The activated carbon obtained by treatment with H2SO4 was named NSST and that obtained by treatment with H3PO4 was named NSPT. XRD revealed an amorphous character for the ACs, and EDXS showed they are mainly carbonaceous. Under the optimal adsorption conditions, NSPT showed the best performance. Correlation coefficients R2 and R2adj were of 85.13 and 69.12% for NSPT and 83.71 and 66.17% for NSST. A pseudo-second-order nonlinear kinetic model best described the adsorption kinetic of BPA removal by the ACs. Langmuir’s isotherm best described the adsorption of BPA onto both adsorbents. Thermodynamic studies suggested an exothermic and physisorption process.

Biosorption of Cu2+, Pb2+, Cd2+ and their mixture from aqueous solutions by Michelia figo sawdust

The study aimed at investigating copper, lead, and cadmium removal from both single and mixed metal solutions by Michelia figo (Lour.) Spreng. wood sawdust treated with 0.5 mol l⁻¹ NaOH for four hours. In order to evaluate the effects of each factor and interactions between factors on metal ion biosorption, a 2³ factorial experimental design was applied. FTIR results showed that the metal ions would bind to the hydroxyl and carboxyl groups of M. figo wood sawdust biomass. The main effects and interactions of three factors pH (3 and 5), initial metal ion concentration (C₀, 0.157 and 1.574 mmol L⁻¹), and dosage of biomass (D, 4 and 10 g L⁻¹) at two levels were analyzed. The most significant variable regarding Cu²⁺ and Pb²⁺ biosorption was initial metal iron concentration. For Cd²⁺, pH was found to be the most significant factor. The maximum removal efficiencies were 94.12 and 100% for Cu²⁺ and Cd²⁺, respectively, at conditions of (+ 1, − 1, + 1): pH 5, initial metal concentration 0.157 mmol L⁻¹ and dosage of biomass 10 g L⁻¹, while 96.39% for Pb²⁺ at conditions of (− 1, − 1, + 1): pH 3, initial metal concentration 0.157 mmol L⁻¹ and dosage of biomass 10 g L⁻¹. There were some interactions between factors: pH*C₀ and C₀*D for Cu²⁺, pH*C₀, pH*D and C₀*D for Pb²⁺, pH*C₀ and C₀*D for Cd²⁺. Biosorption from a multi metal system showed that the presence of Cu²⁺ and Cd²⁺ had no significant influence on the Pb²⁺ removal, while Pb²⁺ in solution significantly decreased the removal efficiencies of the other two metals.

Enhanced recovery of aluminum from wastewater using a fluidized bed homogeneously dispersed granular reactor

The recovery of aluminum from wastewater is one of the main environmental issues that need to be addressed in the aluminum finishing industry. A new technique of converting a soft slurry into hard granules using the homogeneous granulation process in the fluidized-bed reactor (FBR) can respond to this problem. It is a better method of remediation than producing a slurry containing 70% water. This study deals with the recovery of aluminum from aqueous solutions using Fluidized-bed homogeneous granulation process (FBHGP) without seeds. The hydraulic operating conditions were optimized using Box-Behnken Design (BBD) to attain the optimum aluminum removal (AR%) and granulation ratio (GR%). Optimum values of AR% = 98.8% and GR% = 96.9% were attained at the following conditions: influent aluminum concentration, 334.1 mg L^-1_; precipitant pH, 10.4; molar ratio (MR) of precipitant to metal [OH^-]_in/[Al³⁺]_in, 2.5. The characteristics of the granules were comparable with those of orthorhombic structure of aluminum oxide (Al_2.66O₄). FBHGP was proven to be effective as dictated by the reaction mechanism in the recovery of aluminum from aluminum-rich aqueous solutions.

Optimization of heavy metal biosorption onto freshwater algae (Chlorella coloniales) using response surface methodology (RSM)

In this study, the interaction of the initial metal concentration, time of reaction and Chlorella coloniales algae dose were taken for the biosorption of Cr, Cd, Co, Fe and As from aqueous solutions using the Box-Behnken design. The regression equation coefficients were calculated and the data confirmed the validity of second-order polynomial equation for the removal of Cr, Cd, Co, Fe and As with Chlorella coloniales algae. Analysis of variance (ANOVA) showed a high coefficient of determination value (R²) for Cr, Cd, Co, Fe, and As, being respectively 0.998, 0.998, 0.995, 0.998 and 0.994. Heavy metal biosorption increased with the increase in time of reaction from 30 h to 100 h then smoothly steadily decreased. The biosorption capacity of Chlorella coloniales increased when initial Cd concentration was increased from 5 to 12 mg/L, and then no change was seen with further increasing in initial Cd concentration. At low concentrations of heavy metal, Chlorella coloniales showed its effectiveness for Cr, Co, Fe and As bioaccumulation, but at high concentrations of heavy metal bioaccumulation efficiency decreased Under optimal value of process parameters, maximum efficiencies for the removal of Cr, Cd, Co, Fe, and As were 97.8, 97.05, 95.15, 98.6 and 96.5% respectively. The results of the present study suggest that use of C. Coloniales algae can be a good alternative to the current expensive methods of removing heavy metals from aqueous solution.

Simultaneous removal of binary mixture of Brilliant Green and Crystal Violet using derivative spectrophotometric determination, multivariate optimization and adsorption characterization of dyes on surfactant modified nano-γ-alumina

The present study deals with the simultaneous removal of Brilliant Green (BG) and Crystal Violet (CV) by surfactant-modified alumina. The utilization of alumina nanoparticles with an anionic surfactant (sodium dodecyl sulfate (SDS)) as a novel and efficient adsorbent is successfully carried out to remove two cationic dyes from aqueous solutions in binary batch systems. A first-order derivative spectrophotometric method is developed for the simultaneous determination of BG and CV in binary solutions. The linear concentration range and limits of detection for the simultaneous determination of BG and CV were found to be: 1-20, 1-15 mg/L, 0.3 and 0.5 mg/L, respectively. The influence of various parameters, such as contact time, initial concentration of dyes and sorbent mass on the dye adsorption is investigated. A response surface methodology achieved through performing the Box-Behnken design is utilized to optimize the removal of dyes by surfactant-modified nanoparticle alumina through a batch adsorption process. The proposed quadratic model resulting from the Box-Behnken design approach fitted very well with the experimental data. The optimal conditions for dye removal were contact time t=50 min, sorbent dose=0.036 g, CBG (Initial BG concentration)=215 mg/L and CCV (Initial CV concentration)=170 mg/L. Furthermore, FT-IR analysis, the isotherms and kinetics of adsorption were also explored.

Application of Taguchi L32 orthogonal array design to optimize copper biosorption by using Spaghnum moss

In this work, Taguchi L32 experimental design was applied to optimize biosorption of Cu(2+) ions by an easily available biosorbent, Spaghnum moss. With this aim, batch biosorption tests were performed to achieve targeted experimental design with five factors (concentration, pH, biosorbent dosage, temperature and agitation time) at two different levels. Optimal experimental conditions were determined by calculated signal-to-noise ratios. "Higher is better" approach was followed to calculate signal-to-noise ratios as it was aimed to obtain high metal removal efficiencies. The impact ratios of factors were determined by the model. Within the study, Cu(2+) biosorption efficiencies were also predicted by using Taguchi method. Results of the model showed that experimental and predicted values were close to each other demonstrating the success of Taguchi approach. Furthermore, thermodynamic, isotherm and kinetic studies were performed to explain the biosorption mechanism. Calculated thermodynamic parameters were in good accordance with the results of Taguchi model.

Multi-response optimization using Taguchi design and principle component analysis for removing binary mixture of alizarin red and alizarin yellow from aqueous solution by nano γ-alumina

The nanostructure of γ-alumina was used as an effective adsorbent for simultaneous removing of a mixture of alizarin red and alizarin yellow from aqueous solutions. The Taguchi design and principle component analysis were applied to explore effective parameters for achieving a higher adsorption capacity and removal percentage of the binary mixture containing alizarin red and alizarin yellow. Seven factors including temperature, contact time, initial pH value, the shaker rate, the sorbent dose, and initial concentrations of alizarin red and alizarin yellow in three levels were considered through the Taguchi technique. A L27 orthogonal array was used to determine the signal-to-noise ratio. Then, the removal percentage (R%) and adsorption capacity (q) of the above-mentioned dyes were transformed into an accurate S/N ratio. The Taguchi method indicates that the solution pH has the most contribution in controlling the removal percentage of alizarin red and alizarin yellow. Under optimal condition, the maximum removal percentages of 99% and 78.5%, and the capacity uptake of 54.4 and 39.0mg g(-1) were obtained for both alizarin red and alizarin yellow, respectively. Isotherm modeling and kinetic investigations showed that Langmuir, modified Langmuir, and pseudo-second-order models describe both the adsorption equilibrium and kinetic behavior well. The Fourier transform infrared analysis also firmly confirmed the involving active sites of nano γ-alumina in the adsorption process.

Chemical Recycling of Expanded Polystyrene Waste: Synthesis of Novel Functional Polystyrene-Hydrazone Surface for Phenol Removal

Expanded polystyrene (EPS) waste was chemically recycled to a novel functional polystyrene-hydrazone (PSH) surface by acetylation of polystyrene (PS) and then condensation with phenyl hydrazine. The synthesized surface was characterized by the FT-IR and elemental analysis. Synthesized novel functional PSH surface was successfully applied for the treatment of phenol-contaminated industrial wastewater by solid-phase extraction. Multivariant sorption optimization was achieved by factorial design approach. 99.93% of phenol was removed from aqueous solution. FT-IR study showed the involvement of nitrogen of hydrazone moiety of synthesized surface for the uptake of phenol through the hydrogen bonding.

Application of response surface methodology in the optimization of photocatalytic removal of environmental pollutants using nanocatalysts

Response surface methodology is a widely used technique for modelling and optimization of the photocatalytic treatment processes of water and wastewater. This methodology not only estimates linear, interaction and quadratic effects of the factors on the response, but also provides a prediction model for the response at the range of the variables studied and the optimum conditions to achieve the highest performance. The present paper reviews the results of application of this innovative methodology in modelling and optimization of the photocatalytic treatment processes. Different experimental designs including 3k factorial, Doehlert, Box-Behnken and central composite designs have been developed to describe the treatment processes of dyeing effluents, pharmaceutical agents and hazardous phenolic compounds. The results showed that response surface methodology can describe the behaviour of complex reaction systems, such as photocatalytic processes, in the range of experimental conditions adopted. Optimization based on response surface methodology can also estimate the conditions of the photocatalytic processes to achieve the highest performance.