Optimisation and Modelling of Pb (II) and Cu (II) Biosorption onto Red Algae (Gracilaria changii) by Using Response Surface Methodology

Eco-friendly methodology for removing and recovering rare earth elements from saline industrial wastewater

In this study, response surface methodology (RSM) was applied with a Box-Behnken design to optimize the biosorption (removal and bioconcentration) of rare earth elements (REEs) (Y, La, Ce Eu, Gd, Tb) by living Ulva sp. from diluted industrial wastewaters (also containing Pt and the classic contaminants Hg, Pb, Zn, Cu, Co, and Cd). Element concentration (A: 10-190 μg/L), wastewater salinity (B: 15-35), and Ulva sp. dosage (C: 1.0-5.0 g/L) were the operating parameters chosen for optimization. Analysis of the Box-Behnken central point confirmed the reproducibility of the methodology and p-values below 0.0001 validated the developed mathematical models. The largest inter-element differences were observed at 24 h, with most REEs, Cu, Pb and Hg showing removals ≥ 50 %. The factor with the greatest impact (positive) on element removal was the initial seaweed dosage (ANOVA, p < 0.05). The optimal conditions for REEs removal were an initial REEs concentration of 10 μg/L, at a wastewater salinity of 15, and an Ulva sp. dosage of 5.0 g/L, attaining removals up to 88 % in 24 h. Extending the time to 96 h allowed seaweed dosage to be reduced to 4.2 g/L while achieving removals ≥ 90 %. The high concentrations in REE-enriched biomass (∑REEs of 3222 μg/g), which are up to 3000 times higher than those originally found in water and exceed those in common ores, support their use as an alternative source of these critical raw materials.

Optimization Design and Mechanical Performances of Plant-Mix Hot Recycled Asphalt Using Response Surface Methodology

This study aimed to explore the influence of material design parameters on the physical and mechanical properties of recycled asphalt. A Box-Behnken design was employed to determine the optimal preparation scheme for 17 groups of recycled asphalt. The effects of styreneic methyl copolymer (SMC) regenerant content, styrene-butadiene-styrene (SBS)-modified asphalt content, and shear temperature on the mechanical properties of recycled asphalt were analyzed using conventional and high/low-temperature rheological tests. The optimal processing parameters were determined by a response surface model based on multiple response indexes. The results revealed that the SBS-modified asphalt content had the most significant effect on the penetration of recycled asphalt. An increase in SMC regenerant content led to a gradual decrease in the rutting factor, while SBS-modified asphalt content had the opposite effect. The usage of SMC regenerant helped to reduce non-recoverable creep compliance by adjusting the proportion of viscoelastic-plastic components in recycled asphalt. Furthermore, the stiffness modulus results indicated that the addition of SMC regenerant improved the recovery performance of recycled asphalt at a low temperature. The recommended contents of SMC regenerant and SBS-modified asphalt are 7.88% and 150%, respectively, with a shear temperature of 157.7 °C.

Dynamic removal of Pb(II) by live Dunaliella salina: a competitive uptake and isotherm model study

The main aim of this study is modeling of a continuous biosorption system for the removal of Pb(II) ions in the aqueous conditions using live Dunaliella salina microalgae. The live microalgae can grow in saline water and opens new opportunities in varying the amount and properties of biosorbent. The effects of five parameters, including pH, optical density of algae as a factor indicating the adsorbent dosage, injection time, contact time, and initial concentration of Pb(II), were optimized by means of response surface methodology (RSM) based on the central composite design (CCD). Dunaliella salina algae showed maximum Pb(II) biosorption with 96% efficiency. For the selective Pb(II) uptake in the presence of Cd(II) and Ni(II), binary and ternary systems of ions were chosen. The mutual effect of each heavy metal ion in all systems on the total uptake percentage was also examined. The ion selectivity was investigated in the presence of diverse heavy metal ions, and the Pb(II) uptake percentage was determined to be 80%. Both Langmuir and Freundlich isotherm models were suitable for describing multicomponent binary and ternary systems depending on the presence of competitive ions in the mixture. Main functional groups and surface properties of the Dunaliella salina were identified by Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectrometry. Hence, effective heavy metal ion uptake, simple design, and cost-effective cultivation confirmed live Dunaliella salina as suitable microalgae for purifying contaminated water in an economic and safe manner.

Adsorption of Cr6+ ion using activated Pisum sativum peels-triethylenetetramine

The adsorption of Cr6+ ions from water-soluble solution onto activated pea peels (PPs) embellished with triethylenetetramine (TETA) was studied. The synthesized activated TETA-PP biosorbent was further characterized by SEM together with EDX, FTIR and BET to determine the morphology and elementary composition, functional groups (FGs) present and the biosorbent surface area. The confiscation of Cr6+ ions to activated TETA-PP biosorbent was observed to be pH-reliant, with optimum removal noticed at pH 1.6 (99%). Cr6+ ion adsorption to activated TETA-PP biosorbent was well defined using the Langmuir (LNR) and the pseudo-second-order (PSO) models, with a determined biosorption capacity of 312.50 mg/g. Also, it was found that the activated TETA-PP biosorbent can be restored up to six regeneration cycles for the sequestration of Cr6+ ions in this study. In comparison with other biosorbents, it was found that this biosorbent was a cost-effective and resourceful agro-waste for the Cr6+ ion confiscation. The possible mechanism of Cr6+ to the biosorbent was by electrostatic attraction following the surface protonation of the activated TETA-PP biosorbent sites.

Optimization of Tensile Strength and Young's Modulus of CNT-CF/Epoxy Composites Using Response Surface Methodology (RSM)

Composites such as carbon fiber are used extensively by automotive, aerospace, marine, and energy industries due to their strong mechanical properties. However, there are still many areas it is lacking in testing, especially related to its electrophoretic deposition. In this research work, the tensile strength and Young's modulus of CNT-CF/epoxy composites were measured using the tensile test by varying the electrophoretic deposition (EPD) process parameters. Response surface methodology (RSM) was used to optimize the three main parameters in this EPD process: the volume ratio (water as the basis), deposition voltage, and time to obtain the maximum tensile properties of the composites. There were four volume ratios (0%, 20%, 80% and 100%) used in this design of experiment (DoE) with ratios' pairs of 0%, 100%, and 20%, 80%. For this study, water and methanol were used as the suspension medium. This design's deposition voltage and time were 10 to 20 V and 5 to 15 min. ANOVA further verified the responses' adequacy. The optimum conditions for the first Design of Experiment (DoE) (0% and 100%) were identified as a volume ratio of 99.99% water, deposition voltage of 10 V, and 12.14 min. These conditions provided the maximum strength of these composites with a tensile strength of 7.41 N/mm² and Young's modulus of 279.9 N/mm². Subsequently, for the second DoE (20% and 80%), tensile strength of 7.28 N/mm² and Young's modulus of 274.1 N/mm² were achieved with the ideal conditions: volume ratio of 44.80% water, deposition voltage of 10.04 V, and time of 6.89 min. It can be concluded that the ideal interaction between these three EPD parameters was necessary to achieve composites with good tensile properties.

Electrochemical oxidation process on palm oil mill effluent waste activated sludge: optimization by response surface methodology

Biological-based treatment as the conventional treatment for palm oil mill effluent (POME) in open-ponding system face a well known rate-limiting step which is hydrolysis. In this study, electrochemical oxidation (EO) by a ruthenium oxide-coated titanium (Ti/RuO₂) electrode was introduced as a pre-treatment for POME waste activated sludge (WAS). Surface morphology and elemental analysis were investigated using field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Response surface methodology type central composite design was used in this study to understand the relationship between the independent and dependent variables. Analysis of variance (ANOVA) was used to validate the model of the studied variables. The correlation coefficients (R²) indicated a close agreement between the experimental results and the predicted values, with high R² values of 0.9044-0.9773. Multiple response optimization suggested that the range of current density (17-27 mA/cm²) and electrolysis time (55-75 min) at a fixed concentration of sodium chloride (10 g/L), resulted in mixed liquor volatile suspended solids (MLVSS) removal >20%, capillary suction timer (CST) reduction >43%, extracellular polymeric substances (EPS) increment <19% and soluble chemical oxygen demand (sCOD) increment >25%. EO appears to be an efficient pre-treatment as well as practical way to improve the POME WAS disintegration and dewaterability.

Microporous Activated Carbon from Pisum sativum Pods Using Various Activation Methods and Tested for Adsorption of Acid Orange 7 Dye from Water

This work demonstrates the preparation of high-surface-area activated carbon (AC) from Pisum sativum pods using ZnCl2 and KOH as activating agents. The influence of CO2 and N2 gases during the carbonization process on the porosity of AC were studied. The highest specific surface area of AC was estimated at 1300 to 1500 m2/g, which presented characteristics of microporous materials. SEM micrographs revealed that chemical activation using an impregnation reagent ZnCl2 increases the porosity of the AC, which in turn leads to an increase in the surface area, and the SEM image showed that particle size diameter ranged between 48.88 and 69.95 nm. The performance of prepared AC for adsorption of Acid Orange 7 (AO7) dye was tested. The results showed that the adsorption percentage by AC (2.5 g/L) was equal to 94.76% after just 15 min, and the percentage of removal increased to be ~100% after 60 min. The maximum adsorption capacity was 473.93 mg g-1. A Langmuir model (LM) shows the best-fitted equilibrium isotherm, and the kinetic data fitted better to the pseudo-second-order and Film diffusion models. The removal of AO7 dye using AC from Pisum sativum pods was optimized using a response factor model (RSM), and the results were reported.

Modeling and Optimization of Heavy Metals Biosorption by Low-Cost Sorbents Using Response Surface Methodology

This paper exploits, through modeling and optimization, the experimental laboratory data on the biosorption of heavy metal ions Pb(II), Cd(II), and Zn(II) from aqueous media using soybean and soybean waste biomasses. The biosorption modeling was performed using the Response Surface Methodology, followed by optimization based on numerical methods. The aim of the modeling was to establish the most probable mathematical relationship between the dependent variables (the biosorption efficiency of the biosorbents when adsorbing metal ions, R(%), and the biosorption capacity of sorbents, q(mg/g)) and the process parameters (pH; sorbent dose, DS (g/L); initial metal ion concentration in solution, c0 (mg/L); contact time, tc (min); temperature, T (°C)), validated by methodologies specific to the multiple regression analysis. Afterward, sets of solutions were obtained through optimization that correlate various values of the process parameters to maximize the objective function. These solutions also confirmed the performance of soybean waste biomass in the removal of heavy metal ions from polluted aqueous effluents. The results were validated experimentally.

Response surface approach to optimize the removal of the critical raw material dysprosium from water through living seaweeds

Dysprosium (Dy) is a rare earth element with a high economic and strategic value, and simultaneously an emerging contaminant, whose removal from wastewaters is gaining increasing attention. In this work, the Response Surface Methodology (RSM) combined with a Box-Behnken Design (3 factors-3 levels) was used to optimize the key operational conditions that influence the uptake of Dy by two living seaweed, Ulva sp. and Gracilaria sp.. The initial concentration of Dy (10-500 μg/L), water salinity (10-30), and seaweed dosage (0.5-5.5 g/L) were the independent variables, while the removal efficiency (%) and bioaccumulation (q, μg/g) were the response variables. Results highlighted the high capacity of both species to capture Dy. After 168 h, the optimal conditions that led to a maximum of 91 % of Dy removed by Gracilaria sp. were: 500 μg of Dy per L of water, salinity 10, and 5.5 g of seaweed per L. For Ulva sp., a maximum removal percentage of 79 % was achieved in the conditions: any initial concentration of Dy, salinity 20, and seaweed dosage of 3.7 g/L. Independently of the species, the response surfaces showed that the most important variable for the removal is the seaweed dosage, while for bioaccumulation is the initial concentration of Dy. Using RSM, it was possible to obtain the optimal operating conditions for Dy removal from waters, which is a fundamental step toward the application of the proposed technology at large scale.

Modeling and Optimization of Biochar Based Adsorbent Derived from Kenaf Using Response Surface Methodology on Adsorption of Cd2+

Cadmium is one of the most hazardous metals in the environment, even when present at very low concentrations. This study reports the systematic development of Kenaf fiber biochar as an adsorbent for the removal of cadmium (Cd) (II) ions from water. The adsorbent development was aided by an optimization tool. Activated biochar was prepared using the physicochemical activation method, consisting of pre-impregnation with NaOH and nitrogen (N2) pyrolysis. The influence of the preparation parameters—namely, chemical impregnation (NaOH: KF), pyrolysis temperature, and pyrolysis time on biochar yield, removal rate, and the adsorption capacity of Cd (II) ions—was investigated. From the experimental data, some quadratic correlation models were developed according to the central composite design. All models demonstrated a good fit with the experimental data. The experimental results revealed that the pyrolysis temperature and heating time were the main factors that affected the yield of biochar and had a positive effect on the Cd (II) ions’ removal rate and adsorption capacity. The impregnation ratio also showed a positive effect on the specific surface area of the biochar, removal rate, and adsorption capacity of cadmium, with a negligible effect on the biochar yield. The optimal biochar-based adsorbent was obtained under the following conditions: 550 °C of pyrolysis temperature, 180 min of heating time, and a 1:1 NaOH impregnation ratio. The optimum adsorbent showed 28.60% biochar yield, 69.82% Cd (II) ions removal, 23.48 mg/g of adsorption capacity, and 160.44 m2/g of biochar-specific area.

Chitosan Nanocarrier Entrapping Hydrophilic Drugs as Advanced Polymeric System for Dual Pharmaceutical and Cosmeceutical Application: A Comprehensive Analysis Using Box-Behnken Design

The objective of the present research is to propose chitosan as a nanocarrier for caffeine—a commonly used drug in combating cellulite. Being a hydrophilic drug, caffeine suffers from insufficient topical penetration upon application on the skin. Chitosan nanoparticles loaded with caffeine were prepared via the ionic gelation technique and optimized according to a Box–Behnken design. The effect of (A) chitosan concentration, (B) chitosan solution pH, and (C) chitosan to sodium tripolyphosphate mass ratio on (Y1) entrapment efficiency percent, (Y2) particle size, (Y3) polydispersity index, and (Y4) zeta potential were studied. Subsequently, the desired constraints on responses were applied, and validation of the optimization procedure was confirmed by the parameters exhibited by the optimal formulation. A caffeine entrapment efficiency percent of 17.25 ± 1.48%, a particle size of 173.03 ± 4.32 nm, a polydispersity index of 0.278 ± 0.01, and a surface charge of 41.7 ± 3.0 mV were attained. Microscopical evaluation using transmission electron microscope revealed a typical spherical nature of the nanoparticles arranged in a network with a further confirmation of the formation of particles in the nano range. The results proved the successful implementation of the Box–Behnken design for optimization of chitosan-based nanoparticles in the field of advanced polymeric systems for pharmaceutical and cosmeceutical applications.

Biosorption as a method of biowaste valorization to feed additives: RSM optimization

The aim of this work was to prepare an innovative microelemental feed additive for laying hens, based on waste biomass from the agricultural sector (alfalfa and goldenrod after CO₂ extraction in supercritical state). The process was optimized by Response Surface Methodology (RSM) and the most favourable enrichment conditions were selected for Cu(II), Mn(II) and Zn(II) ions: pH - 5, sorbate concentration of Cu(II), Mn(II), Zn(II) - 10.0 mg/L for alfalfa and 10.7 mg/L for goldenrod and biomass dose - 0.1 g/L. Physicochemical properties of biomass were studied and functional groups involved in the binding of Cu(II), Mn(II), Zn(II) ions were determined (mainly carboxylic and hydroxylic groups). An interesting and unique element of this work is the verification of the properties of prepared feed additives in conditions simulating the digestive tract of animals. The release of components in solutions simulating conditions in the intestine and stomach (pH 11 and pH 1) was tested (in vitro tests). The best desorption results were achieved at a strongly acidic pH which corresponds to the stomach environment: 9.80, 14.4% Cu(II), 69.0, 66.9% (Zn), 46.5, 31.9 Mn(II) for alfalfa and goldenrod, respectively. It was concluded that the biomass enriched with micronutrients in biosorption has the potential as a feed additive for sustainable agriculture.

Eucheuma cottonii Seaweed-Based Biochar for Adsorption of Methylene Blue Dye

Pollution from dye containing wastewater leads to a variety of environmental problems, which can destroy plant life and eco-systems. This study reports development of a seaweed-based biochar as an adsorbent material for efficient adsorption of methylene blue (MB) dye from synthetic wastewater. The Eucheuma cottonii seaweed biochar was developed through pyrolysis using a tube furnace with N2 gas, and the properties were later improved by sulfuric acid treatment. The adsorption studies were conducted in a batch experimental setup under initial methylene blue concentrations of 50 to 200 mg/L, solution pH of 2 to 10, and temperature of 25 to 75 °C. The characterization results show that the developed biochar had a mesoporous pore morphology. The adsorbent possessed the surface area, pore size, and pore volume of 640 m2/g, 2.32 nm, and 0.54 cm3/g, respectively. An adsorption test for 200 mg/L of initial methylene blue at pH 4 showed the best performance. The adsorption data of the seaweed-based biochar followed the Langmuir isotherm adsorption model and the pseudo-second-order kinetic model, with the corresponding R2 of 0.994 and 0.995. The maximum adsorption capacity of methylene blue using the developed seaweed‑based biochar was 133.33 mg/g. The adsorption followed the chemisorption mechanism, which occurred via the formation of a monolayer of methylene blue dye on the seaweed-based biochar surface. The adsorption performance of the produced seaweed biochar is comparable to that of other commercial adsorbents, suggesting its potential for large-scale applications.