Statistical optimization of textile dye effluent adsorption by Gracilaria edulis using Plackett-Burman design and response surface methodology

Identification of influential parameters and conditions in heavy metals adsorption onto Cal-LDH-PC using optimization approaches of RSM and Taguchi

Adsorption process plays an important role in the remediation of heavy metals (HMs) from wastewater. A laboratory trial was conducted to investigate effective parameters for improving the bio-adsorption removal of HMs. SEM, EDX, BET, and FTIR techniques were applied to characterize the calcined layer double hydroxide (Cal-LDH), pectin (PC), and Cal-LDH-PC composite prepared from Licorice pomace. The adsorption of zinc (Zn) cadmium, nickel (Ni) and lead (Pb) onto the most efficient sorbent was investigated using RSM methodology with operational factors such as concentration, reaction time, sorbent dose, and pH. The results related to FTIR showed that Cal-LDH-PC had the highest number of functional groups. Based on the SEM results Cal-LDH had a low surface area (9.36 m2 g-1) and a small pore size (9.22 nm). After the modification process (Cal-LDH-PC), the values of surface area and pore size increased by 13-fold (120 m2 g-1) and 1.5-fold (18 nm), respectively. Cal-LDH had high adsorption performance, more cavities, stability, various functional groups, and excessive carbon and oxygen content, which make it efficient and powerful in removing HMs from wastewater. The optimal condition for achieving the removal efficiency (RE%) values of metals was determined to be 80.79 mg L-1, 100 min, 0.167 g L-1, and 9 for concentration, reaction time, sorbent dose, and pH, respectively. Maximum adsorption capacity and RE (%) were 300 mg g-1 and 99% for Zn. According to the results concentration had a major impact on RE% (except for Ni), while for Ni, adsorbent dose had the most significant impact. The present study introduced Cal-LDH-PC prepared from Licorice pomace as a capable, useful and economical sorbent for HMs removal from polluted environments. Taguchi's statistical method is distinguished as an economic method with easier interpretation, while the RSM approach is more accurate, and it can also check the interaction of parameters.

Optimization of preparation conditions of medium and highly substituted carboxymethyl inulin through response surface methodology

This article introduces the synthesis optimization of carboxymethyl inulin using response surface methodology. The important factors affecting the degree of substitution (DS) were determined by Plackett-Burman design, including sodium hydroxide concentration, monochloroacetic concentration, and etherification temperature. Further optimization was conducted using the Box-Behnken response surface design. The coefficient of determination (R2) of the response surface model was 0.9827, and the adjusted R2 value was 0.9516, which proved the significance of the model. The optimized results of the predicted response showed that the molar ratios of sodium hydroxide to monochloroacetic acid and fructose to furan were 3.67 and 2.21, respectively. The maximum DS of 1.67 was obtained at 30 °C alkalization for 30 min and 50.30 °C etherification for 4 h, and the reaction efficiency (RE) reached 76.01 %. Under the optimized conditions, the Experimental DS was 1.68, suggesting that the experimental and predicted values of DS were in good agreement. The characterization results confirmed the synthesis of CMI. In this work, we have provided an effective method for the preparation of moderately to highly substituted CMI in 95 % ethanol.

A response surface model to examine the reactive red 239 sorption behaviors on Rhizoclonium hieroglyphicum: isotherms, kinetics, thermodynamics and toxicity analyses

The present study is an attempt to investigate the potentiality of Rhizoclonium hieroglyphicum in the removal of reactive red 239 (RR239) from aqueous solution and to assess the toxicity of the treated dye solution. Optimisation of the process variables namely dye and biosorbent concentrations, pH, temperature and incubation time for RR239 removal was performed using Response Surface Methodology (RSM) assisted Box Behnken Design (BBD) model. The recycling and regeneration efficiency of the dye adsorbed alga was evaluated using different eluents under optimized conditions. Further to understand the adsorption mechanism, isotherms, kinetics and thermodynamic studies were performed. UV-vis and FT-IR spectroscopy was employed to confirm the interaction between the adsorbate and biosorbent. The nature of the treated dye solution was assessed using phyto, microbial and brine shrimp toxicity studies. On the basis of quadratic polynomial equation and response surfaces given by RSM, 90% decolorization of RR239 was recorded at room temperature under specified optimal conditions (300 mg/L of dye, 500 mg/L of biosorbent, pH 8 and 72 h of contact time). Desorption experiments demonstrated 88% of RR239 recovery using 0.1 N acetic acid as an eluent and 81% of dye removal in regeneration studies. The data closely aligned with Freundlich isotherm (R2 - 0.98) and pseudo-second-order kinetic model (R2 - 0.9671). Thermodynamic analysis revealed that the process of adsorption was endothermic, spontaneous, and favorable. UV-Vis and FT-IR analyses provided evidence for adsorbate-biosorbent interaction, substantiating the process of decolorization. In addition, the results of phyto, microbial and brine shrimp toxicity assays consistently confirmed the non-toxic nature of the treated dye. Thus, the study demonstrated that R. hieroglyphicum can act as a potent bioremediation agent in alleviating the environmental repercussions of textile dyeing processes.

Assessment on the photocatalytic and phytotoxic activities using ecobenevolently synthesized iron oxide nanoparticles from the root extracts of Glycyrrhiza glabra

The present study is the first attempt to utilize the root extracts of Glycyrrhiza glabra as a novel biological route for the synthesis of iron oxide nanoparticles (Fe2O3NPs) under optimized conditions. The process variables namely concentration of ferric chloride, root extract of G. glabra and temperature were optimized using Response Surface Methodology (RSM) to obtain high yield. Phytochemicals mediated the reduction process and served as capping and stabilizing agent. The biosynthesized Fe2O3NPs characterized using UV-Vis spectroscopy exhibited a prominent peak at 350 nm. The crystallinity and valence state of Fe2O3NPs was confirmed by XRD and XPS. The surface functionalization of the nanoparticles was confirmed from the presence of functional groups in the FT-IR spectrum. The FESEM analysis revealed the biosynthesized Fe2O3NPs are irregular and the EDX spectrum recorded the presence of iron and oxygen in the synthesized nanoparticles. The biosynthesized Fe2O3NPs exhibited an appreciable photocatalytic activity against methylene blue under sunlight with a maximum decolorisation efficiency of 92% within 180 min of reaction time. The experimental data of adsorption studies well fitted with Langmuir isotherm and pseudo-second order kinetic model. The thermodynamic study proved to be spontaneous, feasible and endothermic in nature. The phytotoxicity study revealed 92% germination and increased seedling growth in the green gram seeds exposed to Fe2O3NPs. Hence the study established the efficiency of biosynthesized of Fe2O3NPs in photocatalytic and phytotoxic activities.

Removal of crystal violet dye using a three-dimensional network of date pits powder/sodium alginate hydrogel beads: Experimental optimization and DFT calculation

Biodegradable and very low-cost adsorbent beads were prepared from date pits powder (DP) and sodium alginate (SA). DP to SA ratios was varied (1/2, 1/4 and 1/6) and used to eliminate Crystal violet (CV) a cationic dye. Adsorbents were characterized by FTIR, SEM-EDS, UV-vis DR, TGA and the point of zero charge (pHPZC). The optimal composite beads SA@6DP show high adsorption capacities of 83.565 mg/g toward CV than SA@2DP and SA@4DP. The kinetics investigation showed that the adsorption is well described by the pseudo-second-order kinetic (R2 = 0.998). The thermodynamics and isotherms studies exhibit that the adsorption phenomenon for SA@6DP adsorbent is endothermic and significantly fitted with the Redlich-Peterson model. The experimental adsorption tests were optimized by the Box-Behnken design (BBD) which led to conclude the maximal CV removal efficiency achieved by SA@6DP was 99.873 % using [CV] = 50 mg/L, adsorbent mass = 20 mg and 48 h of contact time. The theoretical calculation proved that the CV molecules favor the mode of attack due to their electrophilic character and can accept the SA@6DP adsorbent electrons more easily to form an anti-bonding orbital. SA@6DP hydrogel beads are therefore an exceptional bio-adsorbent that offers excellent adsorption performance.

Current approaches toward the removal of methylene blue dye from synthetic textile effluent using bacterial treated agricultural waste absorbent through statistical design

Massive amounts of wastewater are produced by the textile industry, and this waste needs to be appropriately managed. Agricultural waste wheat straw (WS), a biosorbent that is both economically available and environmentally acceptable, was used in this work to treat textile effluent. Microbial treated modification approaches were utilized for WS to study the dye removal from textile wastewater. Total 15 different isolates were screened for the dye degradation ability from Surat textile industrial effluent. The most significant deterioration was seen in PPSUHB3 when compared to other isolates. The amount of methylene blue dye removal was examined using the isolate PPSUHB3 due to its high efficiency. Based on 16s rDNA sequencing, it was predicted that the isolate PPSUHB3 was Bacillus licheniformis, having great capacity to degrade dye & wheat straw by producing efficient enzyme. The isolate showed the highest decolorization % of MB dye during optimization with WS absorbent which was verified using FTIR and SEM. The dye removal process parameters were statistically optimized using a central composite design (CCD). Wheat straw with particle sizes of 180-250 mm was discovered to be a possible adsorbent for the removal of colour. The maximum removal of MB (55.89%) was obtained using a statistical experimental design at pH 6.36, Temperature 44.6 °C, and Bacteria Concentration 3.04%. The created model is highly significant, according to the ANOVA, which found an R2 value of 0.9812 for it. The validation experiment revealed that the experimental and projected results were strikingly similar. The study found that using bacterial treated wheat straw as an adsorbent may remove wastewater that contains colours at a low cost.

Black carbon derived PET plastic bottle waste and rice straw for sorption of Acid Red 27 dye: Machine learning approaches, kinetics, isotherm and thermodynamic studies

This study focuses on the probable use of PET waste black carbon (PETWBC) and rice straw black carbon (RSBC) as an adsorbent for Acid Red 27 (AR 27) adsorption. The prepared adsorbent is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), AR 27 concentration (5-70 mg/L), adsorbent dose (0.5-20 g/L), pH (2-10), and temperature (25-60°C). High coefficient value [PETWBC (R2 = 0.94), and RSBC (R2 = 0.97)] of process optimization model suggesting that this model was significant, where pH and adsorbent dose expressively stimulus removal efficiency including 99.88, and 99.89% for PETWBC, and RSBC at pH (2). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected value. Pseudo-second-order was the well-suited kinetics, where Freundlich isotherm could explain better equilibrium adsorption data. Thermodynamic study shows AR 27 adsorption is favourable, endothermic, and spontaneous. Environmental friendliness properties are confirmed by desorption studies and satisfactory results also attain from real wastewater experiments. Finally, this study indicates that PETWBC and RSBC could be potential candidates for the adsorption of AR 27 from wastewater.

Removal of hazardous textile dye from simulated wastewater by municipal organic solid waste charcoal using machine learning approaches: Kinetics, isotherm, and thermodynamics

This study focuses on the probable use of municipal organic solid waste charcoal (MOSWC) as an adsorbent for Methyl orange (MO) adsorption. The prepared MOSWC is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), adsorbate concentration (60-140 mg/L), adsorbent dose (1-5 g/L), pH (3-11), and temperature (25-60 °C). The high coefficient value (R2 = 0.96) of the process optimization model suggests that this model was significant, where pH and adsorbent dose expressively stimulus adsorption efficiency including 40.11 mg/g at pH (3), MO concentration (100 mg/L), and MOSWC dose (1 g/L). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected values. The highest monolayer adsorption capacity of MO was 90.909 mg/g. Pseudo-second-order was the well-suited kinetics, where Langmuir isotherm could explain better for equilibrium adsorption data. Thermodynamic study shows MO adsorption is favourable, exothermic, and spontaneous. Finally, this study indicates that MOSWC could be a potential candidate for the adsorption of MO from wastewater.

Performance of Pristine versus Magnetized Orange Peels Biochar Adapted to Adsorptive Removal of Daunorubicin: Eco-Structuring, Kinetics and Equilibrium Studies

Drugs and pharmaceuticals are an emergent class of aquatic contaminants. The existence of these pollutants in aquatic bodies is currently raising escalating concerns because of their negative impact on the ecosystem. This study investigated the efficacy of two sorbents derived from orange peels (OP) biochar (OPBC) for the removal of the antineoplastic drug daunorubicin (DNB) from pharmaceutical wastewater. The adsorbents included pristine (OPBC) and magnetite (Fe₃O₄)-impregnated (MAG-OPBC) biochars. Waste-derived materials offer a sustainable and cost-effective solution to wastewater bioremediation. The results showed that impregnation with Fe₃O₄ altered the crystallization degree and increased the surface area from 6.99 m²/g in OPBC to 60.76 m²/g in the case of MAG-OPBC. Placket-Burman Design (PBD) was employed to conduct batch adsorption experiments. The removal efficiency of MAG-OPBC (98.51%) was higher compared to OPBC (86.46%). DNB adsorption onto OPBC followed the D-R isotherm, compared to the Langmuir isotherm in the case of MAG-OPBC. The maximum adsorption capacity (q_max) was 172.43 mg/g for MAG-OPBC and 83.75 mg/g for OPBC. The adsorption kinetics for both sorbents fitted well with the pseudo-second-order (PSO) model. The results indicate that MAG-OPBC is a promising adsorbent for treating pharmaceutical wastewater.

Design of experiments (DoE) to develop and to optimize extraction of psychoactive substances

The design of experiments (DoE) method was employed to optimize the adsorption processes of seven psychoactive substances in magnetic solid phase extraction. Fe₃O₄/GO/ZIF-8 was utilized as an adsorbent for the efficient extraction of psychoactive substances from environmental water samples. The analytes were ephedrine, methylephedrine, amphetamine, methamphetamine, morphine, papaverine, and thebaine, which were determined by ultrahigh performance liquid chromatography-tandem mass spectrometry. Plackett-Burman design was employed to identify the significant factors responsible for adsorption, and Box-Behnken design was used for further optimization to obtain the optimum values for each variable. The predicted and experimental values were found to be in good agreement. The coefficient of determination (R²) values of 0.9500-0.9976 indicated that the model was significant. The linear ranges were 1-100 ng mL^-1, and the correlation coefficient was good (r² ≥ 0.995). The EF with values of about 2.5 was obtained with recoveries in the range of 74.92-94.47%. The limits of detection (LOD) and limits of quantification (LOQ) were 0.086-0.353 ng mL^-1 and 0.286-1.175 ng mL^-1, respectively. The intra-day and inter-day RSDs were in the range of 0.17-1.87% and 0.06-2.21%, respectively. By using the DoE method, the errors associated with inferring the influence and interaction between various factors can be reduced. The combination of MSPE and DoE improves the recovery, precision, and simultaneous detectability of the target analytes. It has a high potential for psychoactive substance analysis in environmental water.

The Using of Nanoparticles of Microalgae in Remediation of Toxic Dye from Industrial Wastewater: Kinetic and Isotherm Studies

Batch adsorption experiments were carried out to study the removal of the toxic Methylene Blue Dye (MBD) from synthetic aqueous solutions using the nanoparticles form of Arthrospira platensis NIOF17/003. The adsorption capacity of the adsorbent for MBD was investigated using different amounts of A. platensis nanoparticles at different contact times, temperatures, pH, and MBD initial concentrations in the synthetic aqueous solution. In addition, A. platensis nanoparticles were characterized using Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier Transform Infrared (FTIR), and Ultraviolet spectra (UV) techniques. The optimum removal of MBD was found at a concentration of 0.4 g A. platensis nanoparticles. A. platensis nanoparticles remove 93% of MBD in 5 min (under agitation conditions at 150 rpm). The highest adsorption capacity was found by the Langmuir model to be 58.8 mg g⁻¹. It is an endothermic process with spontaneity increasing with temperature. The probable mechanism for the adsorption is chemisorption via surface-active charges in the initial phase, which is followed by physical sorption by occupying pores of A. platensis. MBD adsorption by A. platensis follows pseudo-second-order kinetics. The Freundlich and Langmuir models fit well with the experimental data. The adsorption experiments suggested that the regeneration of the adsorbents was possible for repeated use, especially regarding MBD up to 65.8% after three cycles, which proves it can be easily recycled. In conclusion, the nanoparticles of A. platensis have a significant adsorption potential in the removal of MBD from effluent wastewater.

Development of nanoporous textile sludge based adsorbent for the dye removal from industrial textile effluent

The development of a novel textile sludge based activated carbon (TSBAC) adsorbent and its performance for the treatment of textile dyeing effluent, have been explained in this paper. TSBAC was prepared by the thermal treatment of textile effluent treatment sludge followed by the chemical activation using phosphoric acid. Characterization of TSBAC resulted in enhanced specific surface area (123.65 m²/g) along with the presence of active surface functional groups including -OH, -COOH, -CO. TSBAC showed superior adsorption capacity for methylene blue (123.6 mg/g), reactive red 198 (101.4 mg/g), and reactive yellow 145 (96.8 mg/g) individually, and from the synthetic textile effluent (106 mg/g). The pseudo-second order model and Langmuir isotherm model were found to be fitted well with batch experimental data. The results of the continuous column studies showed that adsorption capacity for methylene blue, reactive red 198, reactive yellow 145 are 101.8 mg/g, 76.6 mg/g, and 75.1 mg/g respectively, and the synthetic textile effluent resulted in an adsorption capacity value of 79.1 mg/g. The reuse potential of TSBAC was proved by effective dye removal up to six reuse cycles. The leachability studies proved that the used adsorbent could be safely disposed of without any harmful effect to the environment.

Multi-Strain Tropical Bacillus spp. as a Potential Probiotic Biocontrol Agent for Large-Scale Enhancement of Mariculture Water Quality

Aquaculture is suffering from long-term water eutrophication in intensive models, whereas the knowledge of multi-strain/specie for improving water quality is extremely limited. Herein, we aimed to develop multi-strain tropical Bacillus spp. as a potential probiotic biocontrol agent for large-scale enhancement of mariculture water quality. Given the practical application, the optimum multi-strain tropical Bacillus spp. (B. flexus QG-3, B. flexus NS-4, and B. licheniformis XCG-6 with the proportion 5: 5: 4) as a probiotic biocontrol agent was screened and obtained, which effectively improved water quality by removing chemical oxygen demand (COD), ammonia-nitrogen, and nitrate and significantly inhibited Vibrio spp. even at relatively low bacterial concentrations (10⁴ CFU/ml) in artificial feed wastewater and large-scale shrimp aquaculture ponds. More importantly, we found that the initial proportion of these three Bacillus sp. strains of multi-strain tropical Bacillus spp. markedly affected the final purification effects, whereas the initial concentration of that only influenced the purification rates at the early stage (0–48 h) instead of final purification effects. We reason that this multi-strain tropical Bacillus spp. as a good probiotic biocontrol agent could perform multiple actions, such as COD-degrading, nitrifying, denitrifying, and antagonistic actions, for large-scale enhancement of tropical aquaculture water. Additionally, the multi-strain tropical Bacillus spp. was safe for shrimp and could be stored for at least 240 days in spore form at room temperature. This multi-strain probiotic biocontrol agent may facilitate its adoption for further marine recirculating aquaculture system development and large-scale commercial application.

Bacillus cereus liquid fertilizer was produced from Agaricus bisporus industrial wastewater

During the Agaricus bisporus canning processes, a large number of water-soluble elements were dissolved into the processing hot water. This study was conducted to use the industrial wastewater of A. bisporus to prepare agricultural microbial fertilizer. In the work, the influence of 6 different liquid fermentation factors on the total biomass of living Bacillus cereus was evaluated with the one-factor-at-a-time method and the Plackett-Burman design. The total biomass of living B. cereus was most influenced by fermentation temperature, shaking speed, and inoculation volume, which were identified as the most critical independent variables for the B. cereus biomass. The approximate ranges of optimal fermentation conditions for the three key factors were identified by the path of steepest ascent. The center point of these factors were 24 ℃ of temperature, 250 rpm of shaking speed and 12 % inoculum amount, respectively. The Box-Behnken design was applied to derive a statistical model for optimizing the three fermentation factors for B. cereus biomass. After further optimizations based on statistical predictions, the optimum fermentation parameters for B. cereus cultured in the A. bisporus industrial wastewater were fermentation temperature of 24.8 °C, shaking speed of 234 rpm, inoculum dose of 12.2 % (v:v, %), industrial wastewater concentration of 4%, initial pH values of 6.5, loading liquid of 60 mL/250 mL, and culture time of 24 h. Culturing with the optimal fermentation conditions resulted in the biomass of B. cereus of 1.35 ± 0.02 × 10⁹ Obj/mL (N = 3), which was consistent with the predicted values (1.32 × 10⁹ Obj/mL) predicted by the corresponding regression models (p < 0.05), and more, was also far higher than that of the standard of agricultural bacterial fertilizers in People's Republic of China. Further, the results of field trial indicated that the of B. cereus liquid fertilizer can remarkably enhance the yield of Brassica chinensis L. It is practicable to make use of the industrial wastewater of A. bisporus to prepare the microbial fertilizer.

L-Ascorbic Acid-g-Polyaniline Mesoporous Silica Nanocomposite for Efficient Removal of Crystal Violet: A Batch and Fixed Bed Breakthrough Studies

In the present study, mesoporous silica nanoparticles (MSNs) synthesized through sol-gel process and calcined at 600 °C were further surface functionalized by a copolymer chain of L-ascorbic acid (AS) and polyaniline (PAni) by in situ free radical oxidative polymerization reaction. The surface modification of MSNs by AS-g-PAni was confirmed by using various analytical techniques, namely FTIR, XRD, SEM-EDX, TEM and AFM. The composition of AS-g-PAni@MS was found to be composed of C (52.53%), N (20.30%), O (25.69%) and Si (1.49%), with 26.42 nm as the particle size. Further, it was applied for the adsorption of crystal violet (CV) dye under batch, as well as fixed bed method. RSM-BBD was taken into consideration, to optimize the various operational parameters effecting the adsorption through batch method. To explore maximum efficiency of the material, it was further subjected to adsorption of CV under fixed bed method, using the variable bed heights of 3.7, 5.4 and 8.1 cm. Based on high value of regression coefficient (R2) and low value of RMSE given as (0.99, 0.02) for 3.7 cm, (0.99, 0.03), the breakthrough data were very well defined by the Thomas model, with optimum concurrence of stoichiometric adsorption capacity values. The external mass transfer equilibrium data were well fitted by the Langmuir model, with maximum monolayer adsorption capacity of 88.42 mg g-1 at 303K, 92.51 mg g-1 at 313 K, 107.41 mg g-1 at 313 K and 113.25 mg g-1 at 333 K. The uptake of CV by AS-g-PAni@MS was well defined by pseudo second order model with rate constant K2 = 0.003 L mg-1 min-1 for 50 and 0.003 L mg-1 min-1 for 60 mg L-1 CV. The adsorption reaction was endothermic with enthalpy (ΔH) value of 3.62 KJ mol-1 and highly efficient for treatment of CV-contaminated water for more the five consecutive cycles.