A new alternative to use soybean hulls on the adsorptive removal of aqueous dyestuff

Hungarian and Indonesian rice husk as bioadsorbents for binary biosorption of cationic dyes from aqueous solutions: A factorial design analysis

The wastewater of the dye industry can be characterized by a complex chemical composition and consists of numerous dyes. Bioadsorbents are increasingly applied for the biosorption of dyes because they are inexpensive and environmentally friendly. Rice husk (RH) is a potential agricultural waste that can be converted into a bioadsorbents for the biosorption of cationic dyes. Herein, the removal of methylene blue (MB) and basic red 9 (BR9) dyes by Hungarian rice husk (HRH) and Indonesian rice husk (IRH) using binary biosorption was investigated. Adsorbents were characterized by zeta potential, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Batch biosorption evaluated the influence of different variables, including pH, adsorbent dose, contact time, and initial concentrations. Several factors that influence the biosorption of MB and BR9 onto rice husk were assessed using main effect, Pareto charts, normal probability plots, and interaction effect in a factorial design. The optimum contact time was 60 min. Isotherm and kinetic models of MB and BR9 in binary biosorption fitted to the Brunauer-Emmett-Teller multilayer and the Elovich equation based on correlation coefficients and nonlinear chi-square. Results showed that the biosorption capacity of HRH was 10.4 mg/g for MB and 10 mg/g for BR9; values for IRH were 9.3 mg/g and 9.6 mg/g, respectively. Therefore, HRH and IRH were found to be effective adsorbents for removing MB and BR9 via binary biosorption.

Conversion of foliar residues of Sansevieria trifasciata into adsorbents: dye adsorption in continuous and discontinuous systems

The study analyzed the potential of leaf powder prepared from the residual leaves of the species Sansevieria trifasciata, as a potential adsorbent for methylene blue (MB) removal. The equilibrium was reached fast for almost all concentrations after 60 min, obtaining the maximum capacity of 139.98 mg g^-1 for 200 mg L^-1. The increase in temperature disfavored the dye adsorption, with the maximum adsorption capacity of 225.8 mg g^-1, observed for 298 K. The thermodynamic parameters confirmed that the adsorption process is spontaneous and exothermic. A direct sloping curve was established for the fixed bed, with breakthrough time (t_b), column stoichiometric capacities (q_eq), and the mass transfer zone lengths (Z_m) were 1430, 1130, and 525 min; 60.48, 187.01, and 322.65 mg g^-1; and 8.81, 11.28, and 10.71 cm, for 100, 200, and 500 mg L^-1, respectively. Furthermore, in a mixture of several dyes, the adsorbent obtained the removal of 51% of the color.

One-step synthesis of carbonaceous adsorbent from soybean bio-residue by microwave heating: Adsorptive, antimicrobial and antifungal behavior

In this work, the transformation of soybean industrial bio-residue with limited practical applications, into a multifunctional carbonaceous adsorbent (SBAC) via one-step microwave-irradiation has been succeeded. The surface porosity, chemical compositions, functionalities and surface chemistry were featured by microscopic pore-textural analysis, elemental constitution analysis, morphological characterization and Fourier transform infra-red spectroscopy. The adsorptive performance of SBAC was evaluated in a batch experiment by adopting different classes of water pollutants, specifically methylene blue (MB), acetaminophen and 2,4-dichlorophenoxyacetic acid (2,4-D). The equilibrium uptakes were analyzed with respect to the non-linearized Langmuir, Freundlich and Temkin isotherm equations. The unique features of SBAC, specifically the antimicrobial and antifungal efficacies were examined against gram-positive/negative bacteria and fungi species. An ordered microporous-mesoporous structure of SBAC, with the BET surface area and total pore volume of 1696 m2/g and 0.94 m3/g, respectively, has been achieved. The equilibrium data of MB and acetaminophen were found to be in good agreement with the Langmuir isotherm model, with the monolayer adsorption capacities (Qo) of 434.57 mg/g and 393.31 mg/g, respectively. The adsorptive experiment of 2,4-D was best fitted to the Freundlich isotherm equation, with the Qo of 253.17 mg/g. The regeneration performance of the spent SBAC under microwave-irradiation could maintain at 69.42-79.31%, even after five (5) adsorption-regeneration cycles. SBAC exhibited excellent inhibition efficiencies against gram-positive/negative bacteria and fungi species, with the inhibition zones at 14.0-28.0 mm. This newly developed SBAC appears to be a new powerful candidate for the remediation of different classes of water contaminants, and novel antibacterial and antifungal agents against biological contaminations. The novel concept of "turn waste into wealth" in a cost-effective and energy saving manner for environmental preservation has been successfully accomplished.

High dye removal capacity of Peniophora laxitexta immobilized in a combined support based on polyurethane foam and lignocellulosic substrates

Dye removal from effluents is a major problem for most textile industries. At present, wastewater treatments are currently based on physico-chemical methods which are expensive, energy inefficient and of limited versatility. The aim of this work was to find a low-cost and efficient method for dye removal. To do this, we designed a combined system based on the immobilization of the ligninolytic white-rot fungus Peniophora laxitexta (BAFC 4687) on mixed supports consisting of two polyurethane foam discs and a middle layer of diverse lignocellulosic substrates: soybean hulls, wheat straw or cellulose spent casings. As a corticioid fungus, P. laxitexta was able to completely colonize the supports developing a compact and tight structure that maintained the integrity of the system after several dye removal cycles. The immobilized fungus removed between 30% and 50% of the azoic dye Xylidine and more than 50% of the anthraquinonic dye RBBR in three successive cycles, and near 90% of the triphenylmethane Malachite Green in 10 repeated cycles without any loss of efficiency. Our analysis showed that the removal of the dyes was due to the combined effect of adsorption to the supports and enzymatic decolorization by soluble laccases and enzymes associated with the mycelium. Additionally, we showed that the presence of Malachite Green induced the expression of a new laccase isoform with high decolorization capacity. Based on these results, we propose that this inoculated laminar biocarrier could be effectively used for dye removal in textile wastewater.

A Way to Close the Loop: Physicochemical and Adsorbing Properties of Soybean Hulls Recovered After Soybean Peroxidase Extraction

Soybean hulls are one of the by-products of soybean crushing and find application mainly in the animal feed sector. Nevertheless, soybean hulls have been already exploited as source of peroxidase (soybean peroxidase, SBP), an enzyme adopted in a wide range of applications such as bioremediation and wastewater treatment, biocatalysis, diagnostic tests, therapeutics and biosensors. In this work, the soybean hulls after the SBP extraction, destined to become a putrescible waste, were recovered and employed as adsorbents for water remediation due to their cellulose-based composition. They were studied from a physicochemical point of view using different characterization techniques and applied for the adsorption of five inorganic ions [Fe(III), Al(III), Cr(III), Ni(II), and Mn(II)] in different aqueous matrixes. The behavior of the exhausted soybean hulls was compared to pristine hulls, demonstrating better performances as pollutant adsorbents despite significant changes in their features, especially in terms of surface morphology, charge and composition. Overall, this work evidences that these kinds of double-recovered scraps are an effective and sustainable alternative for metal contaminants removal from water.

Residue Char Derived from Microwave-Assisted Pyrolysis of Sludge as Adsorbent for the Removal of Methylene Blue from Aqueous Solutions

Residue char is the main by-product of the microwave-assisted pyrolysis of activated sludge and it has a high content of fixed carbon and porous structure, but little is known about its character as an absorbent. In this study, residue char of activated sludge with microwave-assisted pyrolysis was used as an adsorbent to absorb methylene blue. The effects of pyrolysis temperature, pyrolysis holding time, contact time, and adsorption temperature on the adsorption ability of residue char were investigated. Kinetics, isotherm, and thermodynamic models were also included to study the adsorption behavior. The results showed that the optimal pyrolysis condition was 15 min and 603 °C, and the adsorption capacity reached up to 80.01 mg/g. The kinetics analyses indicated the adsorption behavior followed the pseudo-second-order kinetics model and the adsorption process was mainly due to chemical interaction. The adsorption isotherm was described by Freundlich model and thus, its process was multimolecular layer adsorption. Furthermore, the thermodynamics parameters (ΔG0, ΔH0, and ΔS0) at different temperatures indicated that the nature of the adsorption process was endothermic and spontaneous.