Rapid and high-performance adsorptive removal of hazardous acridine orange from aqueous environment using Abelmoschus esculentus seed powder: Single- and multi-parameter optimization studies

Exploring Arachis hypogaea bio-waste sorption potential for phytofiltration of acridine orange dye from wastewater as a new candidate for green revolution

Adsorption is a desirable, environmental friendly strategy for eliminating toxins from industrial effluents using natural resources. The effectiveness of phytofiltering an industrially significant chemical: Acridine orange dye from aqueous media utilizing inexpensive Arachis hypogaea (peanut) bio-waste as an adsorbent has been studied in this work. The major principle of this study is surface chemistry that made biosorption possible by tuning a number of adsorption-related variables, including contact duration of the solution with adsorbent, temperature, pH, adsorbent dose, and stirring rate. 1.2 g of adsorbent dose, 60 °C temperature, 90 min contact time, 100 rpm agitation speed and pH 4 was found to be best conditions giving more than 90% dye removal. FT-IR and SEM were used to assess the surface of biomaterial along with Langmuir, Freundlich, and Temkin isotherms. Freundlich isotherm proved to be more effective with R2 value of 0.995 along with pseudo-second order model and 79.36 mg/g adsorption capacity. Thermodynamically the procedure is exothermic in nature. These favorable results indicated the suitability of Arachis hypogaea bio-waste for removal of acidic contaminants by phytofiltration on a large scale.

Simultaneous removal of malachite green and lead from water by consortium dry-biomasses of Bacillus licheniformis AG3 and Bacillus cereus M116

Synthetic textile dye malachite green (MG) and heavy metals present in industrial wastewater are hazardous to the ecosystem. Bioremediation of dyes and heavy metals using dry-biomasses has advantages over chemical methods. This study screened an acclimatized, heavy metal-resistant, and dye-degrading Gram positive Bacillus licheniformis AG3 strain from the textile wastewater near Kolkata, West Bengal. The EDXRF analysis of this colored wastewater effluent showed 36.33 mg/L lead, significantly higher than the WHO recommendation. Previously, Bag et al. showed bioremediation of synthetic dyes using dry-biomass of Bacillus cereus M116 from an aqueous solution (Bag et al. Arch Microbiol 203(7):3811-3823, 2021). Here, a consortium of dry-biomasses of B. licheniformis AG3 and B. cereus M116 strains (1:1 w/w ratio) was prepared for the simultaneous removal of lead and MG from wastewater. Statistical optimization determines that the pH, initial concentration of contaminants, and dry-biomass concentrations are critical for bioremediation under batch procedures. Further, optimization using the response surface methodology showed that 0.01% consortium dry-biomasses eliminated a maximum of 99.35% MG and 96.01% lead (II) within 6 h. SEM-EDS and FTIR confirmed a strong surface biosorption. Furthermore, a fixed-bed biofilter column of the consortium dry-biomasses was prepared, which was able to remove 98.1% MG and 98.5% lead at the 0.5-1 mL/min flow rate. Together, this study developed a biofilter with a consortium dry biomasses of B. licheniformis AG3 and B. cereus M116 for the simultaneous removal of MG and lead from wastewater.

Green synthesis of novel biochar from Abelmoschus esculentus seeds for direct blue 86 dye removal: Characterization, RSM optimization, isotherms, kinetics, and fixed bed column studies

The presence of Direct blue 86 dye (DB86) in water can lead to various health hazards to the humans and animals. The study explored efficacy of biochar derived from Abelmoschus Esculentus seeds (AESB) to remove DB86 from an aqueous solution. BET analysis of AESB delineated H4 classification with the predominance of micropores and mesopores spread throughout the surface. FTIR study demonstrated the presence of the alkyl (C-H), Alkene (C]C), Carbonyl (C]O) and O-H bond of the sulphonic group which helped in adsorption of DB86 molecules through various mechanisms i.e., pore filling, π-π interactions, and hydrogen bonding interactions. Response surface methodology (RSM) was used for designing the adsorption experiment and analysing the optimum operating parameters. Batch experiments demonstrated excellent adsorption capacity (277.04 mg/g) of AESB and was efficient in 98.06% removal of DB86 at optimal conditions i.e., dye conc. = 300 mg/L, dose = 2.5 g/L, pH = 2, time of 120 min. Adsorption followed nonlinear Sips model (R2 = 0.999) with an error (X2 = 0.13, RMSE = 0.83, MAPE 0.56 and MSRE = 0.0006). The kinetic analysis revealed intra-particle diffusion being the rate-determining step and followed nonlinear pseudo-first-order kinetics (R2 = 0.997). Thermodynamic study revealed that the adsorption of DB-86 proceeded spontaneously and exhibited endothermic characteristics, with the enthalpy change primarily governed by the physisorption mechanism. Thomas model revealed inverse relation of breakthrough and exhaustion time with flow while it was proportional to bed height. The sorption capacity (N0) (2.2493 mg/l min) and rate constant (Ka) (0.028 L/min. mg) of BDST model can accurately be used for predicting the performance of AESB in full scale column.

In-situ biofabrication of bacterial nanocellulose (BNC)/graphene oxide (GO) nano-biocomposite and study of its cationic dyes adsorption properties

In the present study, bacterial nanocellulose/graphene oxide nano-biocomposites (BNC-GO-NBCs) were fabricated by Komagataeibacter saccharivorans NUWB1 using an in-situ method involving three time-dependent approaches. Physicochemical studies showed that the chosen dried BNC-GO-NBC possessed a three-dimensional interconnected porous structure of BNC with GO layers embedded within the BNC fibrils. BNC-GO-NBC had a crystallinity index of 74.21 %, higher thermostability up to 380 °C and could withstand a tensile load of 84.72 MPa. N2 adsorption-desorption isotherm of the BNC-GO-NBC was found to be of type IV, suggesting a mesoporous type structure with a total pore volume and surface area of 6.232e-04 cc g-1 and 10.498 m2. BNC-GO-NBC exhibited remarkable adsorption capacity for two cationic dyes, Rhodamine B (RhB) and Acridine Orange (AO), and the adsorption data conformed well to the Langmuir isotherm (R2 = 0.99) and pseudo-second-order model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Additionally, the BNC-GO-NBC displayed the potential for regeneration, with the ability to be recycled up to five times. Further, the antibacterial activity, cell cytotoxicity and oxidative stress assays of the BNC-GO-NBC revealed its non-cytotoxic nature. The findings of the present investigation evidently suggest the potentiality of BNC-GO-NBC in the application of dye adsorption and other environmental applications.

Experimental and theoretical studies on nitrate removal using epichlorohydrin-modified cross-linked chitosan derived from shrimp waste

Nitrates level in water is a worldwide problem that represents a risk to the environment and people's health; efforts are currently devoted to the development and implementation of new biomaterials for their removal. In this study, chitosan (Ch) from shrimp waste and the related epichlorohydrin-modified crossover chitosan (Ch-EPI) were used to remove nitrates from aqueous solutions. The mechanism of selective nitrate removal was elucidated and validated by theoretical calculations. The physicochemical performance of Ch and Ch-EPI was investigated through the main parameters pH, adsorption capacity, contact time, initial nitrate concentration, coexisting anions, and temperature. The experimental data were fitted to widely used adsorption kinetic models and adsorption isotherms. The maximum percentage of nitrate adsorption was reached at an equilibrium pH of 4.0 at an adsorbent dose of 2.0 g/L after a contact time of 50 min. Competing anion experiments show that chloride and sulfate ions have minimal and maximal effects on nitrate adsorption by Ch-EPI. Experimental adsorption data are best fitted to pseudo-second-order kinetic and isothermal Langmuir models. The maximum adsorption capacities of Ch and Ch-EPI for nitrate removal were 12.0 mg/g and 38 mg/g, respectively.

Adsorptive removal of heavy metals and organic dyes by sodium alginate/coffee waste composite hydrogel

Heavy metals and dyes used in technological applications have a detrimental influence on human health and the environment. The most used methods for removing pollutants depend on high-cost materials. Therefore, this research was conducted on cost-effective alternatives derived from natural resources and food waste. Herein, we designed a composite hydrogel based on sodium alginate/coffee waste (Alg/coffee) as adsorbent for the removal of organic and inorganic pollutants from aquatic solutions. The selectivity study displayed that Alg/coffee is more effective in adsorbing Pb(II) and acridine orange dye (AO). Adsorption of Pb(II) and AO was studied at concentration range of 0-170 mgL-1 and 0-40 mgL-1. Adsorption data of Pb(II) and AO reveals their fitting to Langmuir-isotherm and pseudo-second-order-kinetic models. The findings demonstrated that Alg/coffee hydrogel are more effective than coffee powder itself with an adsorption (%) approaching 98.44 % of Pb(II) and 80.53 % of AO. Real sample analysis reveals the efficiency of Alg/coffee hydrogel beads in Pb(II) adsorption. The adsorption cycle was examined four times providing high efficiency toward Pb(II) and AO. Desorption of Pb(II) and AO was easily performed using HCl eluent. Thus, Alg/coffee hydrogel beads could be promising adsorbent for the removal of organic and inorganic pollutants.

Optimization of Adsorption Parameters for Removal of Cationic Dyes on Lignocellulosic Agricultural Waste Modified by Citric Acid: Central Composite Design

Barley straw (BS-C) and corn stalks (CS-C) modified by citric acid are hopeful adsorbents for the removal of cationic dyes from aqueous solutions. Optimization of adsorption factors to improve removal of methylene blue (MB) and malachite green (MG) on BC-C and CS-C was carried out by response surface methodology with central composite design. The effect of pH, time, dye concentration, and adsorbent dose on the removal efficiency of cationic dyes was investigated. The experimental data were in good agreement with the predicted data obtained by mathematical models. Accordingly, the maximum MB removal efficiency on BS-C of 97% was achieved with a pH of 6.4, time of 50 min, an adsorbent dose of 11 g L−1, and an initial MB concentration of 26 mg L−1; the maximum MG removal efficiency on BS-C of 95% was achieved with a pH of 7.2, time of 60 min, an adsorbent dose of 14 g L−1, and an initial MG concentration of 24 mg L−1; the maximum MB removal efficiency on CS-C of 97% was achieved with a pH of 6.5, time of 45 min, an adsorbent dose of 11 g L−1, and an initial MB concentration of 20 mg L−1; the maximum MG removal efficiency on CS-C of 94% was achieved with a pH of 6.6, time of 50 min, an adsorbent dose of 12 g L−1, and an initial MG concentration of 24 mg L−1.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Statistical evaluation of liquid phase sequestration of acridine orange and Cr6+ by novel mesoporous glutamic acid-g-polyacrylamide/plaster of paris/riboflavin hydrogel nanocomposite

The adsorption of acridine orange and Cr⁶⁺ ion onto plaster of paris reinforced glutamic acid-grafted-polyacrylamide hydrogel nanocomposite modified with riboflavin, Glu-g-PAM/POP/Rb HNC was studied. The Glu-g-PAM/POP/Rb HNC was physico-chemically characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller analysis. The specific surface area, pore volume and pore diameter were 15.48 m²/g, 0.015 cm³/g and 4.23 nm, respectively. Adsorption process was strategized by response surface methodology (RSM) based on a 3-level 5-factor (initial solution pH, contact time, adsorbent dose, initial adsorbate concentration and temperature) central composite design (CCD), and validity of the estimated parameters was statistically evaluated using analysis of variance (ANOVA). The optimized operating variables were: pH (AO = 10; Cr⁶⁺ = 4.15), contact time (AO = 60 min; Cr⁶⁺ = 59 min), adsorbent dose (0.8 g/L), initial adsorbate concentration (60 mg/L) and temperature (298 K). Isotherm results were coincident with Langmuir isotherm model. The experimental kinetic adsorption data was congruous with pseudo-second order model, with the uptake rate controlled by both intraparticle and liquid film diffusions. The relatively high Langmuir saturation capacity of 202.63 mg AO/g and 143.68 mg Cr⁶⁺/g, supported by the decent recyclability up to four times affirmed the promising performance of the adsorbent. The efficacy of the adsorbent for simultaneous removal of AO and Cr⁶⁺ from bi-component system was assessed. The possible adsorption mechanism mainly involved hydrogen bonding, van der Waals forces, electrostatic and π-π interactions. Adsorption of AO and Cr⁶⁺ onto Glu-g-PAM/POP/Rb HNC was feasible and exothermic as revealed by the thermodynamic parameters. The findings demonstrated superior adsorbent efficacy for the seizure of pollutants, particularly AO and Cr⁶⁺ from aqueous solution.

Adsorption of As(III) and As(V) from aqueous solution by magnetic biosorbents derived from chemical carbonization of pea peel waste biomass: Isotherm, kinetic, thermodynamic and breakthrough curve modeling studies

The purpose of this research was to investigate the adsorption of arsenic (As) from aqueous solutions using MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum (pea) pyrolyzed at 500 °C and 600 °C temperatures, respectively). The potential of both biosorbents for As adsorption was determined in batch and column mode. The characterization of both biosorbents was performed by energy dispersive spectroscopy, scanning electron microscope, pHZPC, particle size distribution, X-ray diffraction, zeta potential and Fourier-transform infrared spectroscopy. It was found that the efficiency of MPAC-600 was better than MPAC-500 for the adsorption of As(III) and As(V) ions. The adsorption capacities of MPAC-500 and MPAC-600 in removing As(III) were 0.7297 mg/g and 1.3335 mg/g, respectively, while the values of Qmax for As(V) on MPAC-500 and MPAC-600 were 0.4930 mg/g and 0.9451 mg/g, respectively. The Langmuir isotherm model was found to be the best fit for adsorption of As(III) by MPAC-500 and MPAC-600, as well as adsorption of As(V) by MPAC-500. The Freundlich isotherm model, on the other hand, was optimal for As(V) removal with MPAC-600. With R2 values close to unity, the pseudo-second-order kinetics were best fitted to the adsorption process of both As species. The Thomas model was used to estimate the breakthrough curves. The effects of coexisting oxyanions and regeneration studies were also carried out to examine the influence of oxyanions on As adsorption and reusability of biosorbents.

Low temperature pickling regeneration process for remarkable enhancement in Cu(II) adsorptivity over spent activated carbon fiber

In this paper, a simple and efficient regeneration technology of low-temperature pickling regeneration process is proposed for Cu(II)-adsorbed activated carbon fiber felts (ACFFs). The regeneration process mainly uses the strong oxidation of acidic regenerant above boiling point to regenerate ACFFs in a confined space. With no demand for high temperature and high pressure, the regeneration process achieves a high efficiency regeneration and a remarkable enhancement of Cu(II) adsorptivity simultaneously for Cu(II)-adsorbed ACFFs. After parameter optimization, the pickling temperature of 383 K, pickling time of 3 h and HNO₃ concentration of 150 g/L are adopted as optimum process parameters for the reutilization of ACFFs. The regeneration rates of ACFFs in five cycles are maintained at 424.08%-829.59%. Analytical results show that the enhancement of Cu(II) adsorptivity is mainly caused by the remarkable enhancement of specific surface area (increased by 106.08%), micropore volume (increased by 102.17%) and more abundant surface chemical structure (particularly carboxyl and nitro group) after treated by the regeneration process.

Biosorption of organic dye Acridine orange from aqueous solution using dry biomass of Bacillus cereus M116

Acridine orange (AO), a basic carcinogenic fluorochrome dye, is used in the industry for staining. In this study, Gram-positive bacteria, Bacillus cereus M¹₁₆ (MTCC 5521) dry biomass was tested as an eco-friendly, easily available, and cheap biosorbent for the AO dye removal. We obtained optimum biosorption of AO at a biomass concentration of 0.25 g/L and initial dye concentrations of 50-400 mg/L at neutral to basic pH within the 300 min contact time. Kinetics analysis of the biosorption process was best fitted with the pseudo-second-order reaction type. We also performed the isotherm analysis to predict the nature of the reaction taking place, which was found to follow the Redlich Peterson isotherm model with high determination coefficients. The maximum sorption capacity was 210.46 mg/g of dry biomass. The differential FTIR spectroscopic analysis of pristine and AO-treated Bacillus cereus M¹₁₆ cells suggested the potential involvement of carbonyl, hydroxyl, and amine groups in the biosorption process. Also, the scanning electron microscopy of the cells after AO removal confirmed a gross surface alteration compared to the untreated cells. Furthermore, Response Surface Model (RSM) analysis with the three-way ANOVA test confirms statistically significant interactions between the dye concentration, pH, and temperature with the biosorption capacity (p < 0.001). Hence, the dry biomass of Bacillus cereus M¹₁₆ was found to be an effective bio-remedial for the AO removal.

Synthesis of mesoporous magnetic polypyrrole and its application in studies of removal of acidic, neutral, and basic pharmaceuticals from aqueous medium

As an alternative to traditional adsorbents, mesoporous magnetic polypyrrole (MMPPy) was first used as an adsorbent for the removal of acid, neutral, and basic pharmaceutical compounds considered aqueous pollutants. Ibuprofen (IBU, acid), caffeine (CAF, neutral), and bupropion (BUP, basic) were chosen as adsorbates and applied in adsorption studies. They proved to be pH dependent of the aqueous solution and the best results were found at pH 4 for IBU and CAF and pH 7 for BUP and 60 mg was the optimal amount of adsorbent to be used in the studies. Adsorption was extremely fast and the equilibrium was reached up to 180 s. The adsorption data of all analytes could be well interpreted by the pseudo second-order kinetic model and the dual-site Langmuir-Freundlich isotherm model. The adsorption capacities obtained by the dual-site Langmuir-Freundlich model were 53.67 mg g^-1, 16.74 mg g^-1, and 24.72 mg g^-1 for IBU, CAF, and BUP, respectively. Thermodynamic parameters revealed that IBU adsorption becomes spontaneous as temperature increases and CAF and BUP adsorption occurs through a non-spontaneous process. In addition, this study shows endothermic nature of the adsorption process. Analytes were desorbed using an aqueous solution at pH 10 for IBU, pH 7 for CAF, and pH 4 for BUP and then the material was regenerated successfully. The results suggest that MMPPy can be efficiently used in the removal of different organic analytes found in contaminated water.