Sugarcane molasses derived carbon sheet@sea sand composite for direct removal of methylene blue from textile wastewater: Industrial wastewater remediation through sustainable, greener, and scalable methodology

Introducing machine learning model to response surface methodology for biosorption of methylene blue dye using Triticum aestivum biomass

A major environmental problem on a global scale is the contamination of water by dyes, particularly from industrial effluents. Consequently, wastewater treatment from various industrial wastes is crucial to restoring environmental quality. Dye is an important class of organic pollutants that are considered harmful to both people and aquatic habitats. The textile industry has become more interested in agricultural-based adsorbents, particularly in adsorption. The biosorption of Methylene blue (MB) dye from aqueous solutions by the wheat straw (T. aestivum) biomass was evaluated in this study. The biosorption process parameters were optimized using the response surface methodology (RSM) approach with a face-centred central composite design (FCCCD). Using a 10 mg/L concentration MB dye, 1.5 mg of biomass, an initial pH of 6, and a contact time of 60 min at 25 °C, the maximum MB dye removal percentages (96%) were obtained. Artificial neural network (ANN) modelling techniques are also employed to stimulate and validate the process, and their efficacy and ability to predict the reaction (removal efficiency) were assessed. The existence of functional groups, which are important binding sites involved in the process of MB biosorption, was demonstrated using Fourier Transform Infrared Spectroscopy (FTIR) spectra. Moreover, a scan electron microscope (SEM) revealed that fresh, shiny particles had been absorbed on the surface of the T. aestivum following the biosorption procedure. The bio-removal of MB from wastewater effluents has been demonstrated to be possible using T. aestivum biomass as a biosorbent. It is also a promising biosorbent that is economical, environmentally friendly, biodegradable, and cost-effective.

Cadmium-Tolerant Plant Growth-Promoting Bacteria Curtobacterium oceanosedimentum Improves Growth Attributes and Strengthens Antioxidant System in Chili (Capsicum frutescens)

The remediation of potentially toxic element-polluted soils can be accomplished through the use of microbial and plant-assisted bioremediation. A total of 32 bacteria were isolated from soil samples contaminated with potentially toxic elements. The isolated bacterial strain DG-20 showed high tolerance to cadmium (up to 18 mM) and also showed bioaccumulative Cd removal properties, as demonstrated by atomic absorption spectroscopy studies. By sequencing the 16S rRNA gene, this strain was identified as Curtobacterium oceanosedimentum. Under stress and normal conditions, isolate DG-20 also produced a wide range of plant growth promoting traits, including ammonia production (51–73 µg/mL) and IAA production (116–183 µg/mL), alongside siderophore production and phosphate solubilization. Additionally, pot experiments were conducted to determine whether the strain could promote Chili growth when Cd salts are present. Over the control, bacterial colonization increased root and shoot lengths significantly up to 58% and 60%, respectively. Following inoculation with the Cd-tolerant strain, the plants also increased in both fresh and dry weight. In both the control and inoculated plants, Cd was accumulated more in roots than in shoots, indicating that Chili was phytostabilizing Cd levels. Besides improving the plant attributes, Cd-tolerant bacteria were also found to increase the amount of total chlorophyll, proline, total phenol, and ascorbic acid in the soil when added to the soil. These results suggest that the inoculant provides protection to plants from negative effects. The results of the present study predict that the combined properties of the tested strain in terms of Cd tolerance and plant growth promotion can be exploited for the purpose of the bioremediation of Cd, and for the improvement of Chili cultivation in soils contaminated with Cd.

Investigation of seawater mineral promoted pyrolysis at low temperature for improving the adsorption capabilities of biochar

Naturally abundant seawater mineral was employed to engineer banana pseudostem and bamboo biochars through pyrolysis at different low temperatures for improving their adsorption capabilities for methylene blue (MB) and tetracycline (TC). The adsorption capabilities were greatly enhanced as the biochars were pyrolyzed at 300 °C with 50/1 (mL/g) dosage of seawater to biomass. For instance, the engineered banana pseudostem biochar exhibited 8.00 and 6.54 times higher adsorption capabilities than the corresponding pristine biochar for MB (447.79 mg/g vs 55.96 mg/g) and TC (100.59 mg/g vs 16.75 mg/g) at 25 °C, respectively. The characterization results indicated that a large number of carboxylates, lactone acid salts, and alkoxides were generated on the engineered biochar and a high cation exchange capacity was gained. The adsorption of MB was mainly attributed to cation exchange complying with hydrogen bonding and electrostatic interaction, whereas the adsorption of TC was realized by hydrogen bonding and complexation.

Okara and okara modified and functionalized with iron oxide nanoparticles for the removal of Microcystis aeruginosa and cyanotoxin

Eutrophicating compounds promote the growth of cyanobacteria, which has the potential of releasing toxic compounds. Alternative raw materials, such as residues, have been used in efficient adsorption systems in water treatment. The aim of the present study was to apply the residue Okara in its original form and modified by hydrolysis with immobilization of magnetic nanoparticles as an adsorbent. For the removal, the cyanobacteria Microcystis aeruginosa was chosen, as well as its secondary metabolites, L-amino acids leucine and arginine (MC-LR microcystin), from aqueous solutions. The adsorbents presented a negative surface charge, and the x-ray diffraction (DRX) outcomes successfully demonstrated the immobilization of iron oxide nanoparticles on the adsorbents. The adsorbent with the best result was the Okara hydrolyzed and functionalized with iron oxide, which showed a 47% (qe = 804.166 cel/g) and 85% (qe = 116.94 µg/L) removal for the cyanobacteria cells and chlorophyll-a, respectively. The kinetics study demonstrated a pseudo-first-order adsorption with maximal adsorption in 480 minutes, removing 761 µg/L of chlorophyll-a. In this trial, a low organic material removal has occurred, with a removal rate of 5% (qe = 0.024 mg/g) in the analysis of compounds in absorbance by ultraviolet light (UV) monitored by optical density determination in 254 nm (OD254). Nevertheless, the reaction system with the presence of organic material removed 53,28% of the MC-LR toxin, with adsorption capacities of 2.84 µg/L in a preliminary trial conducted for two hours, arising as a potential and alternative adsorbent with a capacity of removing cyanobacteria and cyanotoxin cells simultaneously.

Poly(lactic acid)-poly(ethylene glycol)/Magnesium Silicate Membrane for Methylene Blue Removal: Adsorption Behavior, Mechanism, Ionic Strength and Reusability Studies

In this work, the effect of magnesium silicate (MgSiO₃) as a filler on poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) membrane was investigated towards the enhancement of adsorption capacity for removal of cationic dye. The preparation and fabrication of membranes were performed through copolymerization and phase inversion techniques. Analysis of functional groups, tensile strength, morphology and surface wettability were employed in the characterization of the membranes. After the addition of MgSiO₃, it was found that the PLA-PEG/MgSiO₃ membrane presented a higher hydrophilic property with improved mechanical strength. Next, the adsorption of methylene blue (MB) was optimized using response surface methodology (RSM) with the parameters mass of membrane and initial concentration of MB solution. The effects of pH and ionic strength were also examined to determine the mechanism involved during adsorption processes, which later were found to be electrostatic interaction and ion-exchange mechanism. From the isotherms and kinetics studies, the PLA-PEG/MgSiO₃ membrane was well fitted by the Freundlich model and pseudo second order model, respectively. This membrane also demonstrated reusable character of up to six cycles.

Characterization and adsorption applications of composite biochars of clay minerals and biomass

Composite mineral-biochars of a homogeneous biomass (cellulose) and heterogeneous biomass (oak leaves) were fabricated with either 5 wt% or 10 wt% minerals (montmorillonite (MMT), kaolinite, and sand) and then pyrolyzed at 600 °C for 60 min. Characterizations including proximate analysis, ultimate analysis, surface area and porosity, morphology, and surface chemistry confirmed that minerals were present on the surface of biochar, and MMT/kaolinite-biochar composites showed a strengthening in the chars' aromatic structures, as well as increases in oxygen-containing surface functional groups. Methylene blue adsorption isotherms indicated that the MMT/kaolinite-biochars had higher adsorption capacities than pure biomass or biomass-sand biochars (110 mg_MB/g_char and 24 mg_MB/g_char for MMT-cellulose char and cellulose char, respectively). A multilinear model relating adsorption capacity and adsorbent properties was developed to measure the relative contribution of biochar properties to adsorption behavior. The model indicates that pore volume and hydrogen bonding were the dominant properties in controlling the adsorption of methylene blue onto the biochars. Findings from this work indicate that composite biochars prepared from biomass and inexpensive clay minerals are a promising adsorbent for remediating organic contaminants from water.

In-situ synthesis of CuS@carbon nanocomposites and application in enhanced photo-fenton degradation of 2,4-DCP

Novel CuS nanoparticles embedded into carbon nanosheets (CuS@CNs) were prepared in situ by applying wheat straw cellulose/feather protein hydrogel beads as templates and were used to photocatalytically activate H₂O₂ to degrade 2,4-dichlorphenol (2,4-DCP). The photo-Fenton catalytic properties of the nanocomposite catalysts obtained under different synthetic conditions, including different Cu²⁺ concentrations, S^2- concentrations and calcination temperatures, were evaluated. The results showed that CuS@CNs with 0.1 M Cu²⁺, 0.1 M S^2- at 800 °C presented excellent photo-Fenton degradation performance for 2,4-DCP (25 mg/L) in the presence of H₂O₂ and could remove 90% of 2,4-DCP in 2.5 h. The water quality parameters (pH, Cl^-, HCO₃^-, H₂PO₄^- and SO₄^2-) exhibited different effects on the photocatalytic degradation process. The catalytic activity of the CuS@CNs used in the cycle could be recovered after thermal regeneration. Radical quenching and electron paramagnetic resonance (EPR) experiments confirmed that ·OH species were main active radicals contributing to the degradation of 2,4-DCP. The photocatalytic mechanism of CuS@CNs was also explored by photoelectrochemical (PEC) measurements and UV-vis diffuse reflectance spectroscopy (DRS). Incorporation of carbon nanosheets could significantly improve the separation of photogenerated charge carriers to stimulate pollutant degradation by CuS. Based on the detected intermediates, the degradation pathway of 2,4-DCP in the CuS@CNs/H₂O₂ reaction system was also proposed.

Comparison of adsorption behavior studies of methylene blue by microalga residue and its biochars produced at different pyrolytic temperatures

The adsorption behaviors of methylene blue (MB) on microalga residue powder (MRP) and biochars derived from microalga residue (MRB) produced at different pyrolytic temperatures were compared. Six biochars were prepared from residual Chlorella sp. and Spirulina sp. at different pyrolytic temperatures in the range of 200-550 °C. The adsorption kinetics, isotherms, thermodynamics, and the effect of pH were studied, and chemical analyses of MB-loaded MRP and MRB were conducted using SEM, FTIR, and XPS techniques. The results found that the pseudo-second-order, Elovich, and Freundlich models could effectively describe the MB adsorption process on MRP and MRB. The thermodynamic results confirmed that the adsorption processes were spontaneous and endothermic. Further, MRP showed an excellent adsorption ability on MB through electrostatic interaction, complexation with oxygen/nitrogen-containing functional groups and π-π interaction. However, massive oxygen-containing functional groups after pyrolysis were lost, leading to a significant decrease in the adsorption capacity of MRB on MB. This phenomenon was further observed with increasing pyrolytic temperature. Overall, this study demonstrated that microalga residue performed better for MB removal compared with their pyrolyzed analogs. Graphical abstract.

Characterization of Two Cactus Formulation-Based Flocculants and Investigation on Their Flocculating Ability for Cationic and Anionic Dyes Removal

Dye invasion in wastewaters is undeniably one of the crucial environmental concerns in addition to the supplement of toxic synthetic chemical flocculants used for color removal using the conventional coagulation-flocculation process. With the aim to improve the flocculation stage in terms of reagents safety and ensure dyes removal, the present study explores the flocculating effectiveness of two natural, stable, and eco-friendly cactus formulations, namely 60 °C oven-dried (DP) and lyophilized (LP) cladodes. Both formulations were assessed to treat cationic (Methylene blue; MB) and anionic (Methyl Orange; MO) dye solutions as a substitution attempt for the currently questioned employed synthetic chemical flocculants. Obtained results demonstrate that, in conjunction with alum as coagulant, the lyophilized powder (LP) bio-based flocculant appears to be the most efficient cactus formulation, showing a significant color (83%) and a turbidity (69%) abatement for the cationic dye (MB) and, respectively, 63% and 62% for the anionic one (MO). Additionally, the flocculation activity of the LP formula remained high over an eight-month period of storage. Moreover, based on the Fourier transform infrared (FTIR) spectroscopic analysis and the chemical characterization of cactus formulations, the occurring flocculation mechanisms of the dye removal are presumed to be based on both adsorption and bridging phenomena. Further, the significant color and turbidity decline achieved upon the addition of the lyophilized cactus cladodes powder (LP), enhancing thus the coagulation performance of the alum-based coagulant, proved the effectiveness of this bio-flocculant compared to the commonly used chemical flocculant (polyacrylamide). Hence, it was suggested that lyophilized cactus cladodes as a natural flocculant could be one of the effective surrogates to chemical flocculants conventionally used in wastewater treatment for the sake of a safer and sustainable environment.