Biosorption and regeneration potentials of magnetite nanoparticle loaded Solanum tuberosum peel for celestine blue dye

Cutting-edge regeneration technologies for saturated adsorbents: a systematic review on pathways to circular wastewater treatment system

Adsorption seemed like an excellent physicochemical process employed for wastewater treatment. In the last few decades, significant improvements have been made in efficiency and economy to remove contaminants from wastewater using several adsorbents. However, less attention was paid to the regeneration of used adsorbents. Aside from the adsorbent's high adsorption performance, the disposal of spent adsorbents is an environmental concern. Regeneration is an important aspect to stimulate the adsorption efficiency of the spent adsorbent for wastewater treatment. This article reviews the various regeneration techniques like electrochemical regeneration, biological regeneration, thermal regeneration, ultrasound regeneration, and chemical regeneration in detail that have been performed for the renewal of saturated adsorbents. In the ultrasonic regeneration technique, Fe3O4-loaded coffee waste hydrochar adsorbent showed 100% regeneration efficiency (RE) after 1.3 h at the power consumption of 300 W/L. Electrochemical regeneration of granular activated carbon, Nyex, graphene and titanium dioxide composite, and Nyex 1000 showed 100% RE after 3, 0.16, 0.12, and 1.5 h, respectively, with electrolyte Na2SO4 and NaCl. In the regeneration technique, powdered activated carbon showed 90% RE after 48-72 h. Immobilized fungal biomass (Rhizopus nigricans) adsorbent showed 111-115% RE with base (0.01 N NaOH, NaHCO3, and Na2CO3) solvent. The present study addresses issues including waste generation, adsorbent potential and efficiency, eco-friendly techniques, and the release of adsorbed pollutants in regenerating saturated adsorbents. The mechanisms of adsorbent regeneration were thoroughly examined, highlighting the significance of the regeneration process in adsorption. Furthermore, this review discusses the advantages of hybrid regeneration techniques like microwave-activated ultraviolet-advanced oxidation, electro-peroxide approach, electrochemical and electrothermal methods, and the secondary use of spent adsorbents as catalysts, fertilizer, cementitious materials, secondary adsorbent bio-fuels, etc. Using saturated adsorbents is a practical technology for sustainable wastewater treatment that has the potential to minimize pollution and promote a circular economy. This review concludes with a discussion of the present challenges in the regeneration of the used adsorbents, as well as future directions for ensuring the system's feasibility from an economic and environmental standpoint for use on an industrial scale.

Wodyetia bifurcata (foxtail palm tree) leaves as a super-augmented instantaneous methylene blue remover from simulated water and wastewater

Wodyetia bifurcata, also known as foxtail palm tree leaves, was tested for highly effective methylene blue (MB) removal from commercial and artificial effluent. BET surface area measurement, FESEM, FTIR, and pHzpc were used to get information on the shape and structure of the particles. Several important factors were used to determine its adsorption activity, including intake concentration, contact duration, and pH level. Accelerated adsorption is seen in the experimental results, with more than 94% adsorption occurring successfully in the initial 12 min and reaching equilibrium within 15 min (% removal = 97.45%) at neutral pH. It was discovered that the maximum adsorption capacity was 58.74 mg g-1 at 308 K. The adsorption procedure confirms an active adsorption process of linear and non-linear kinetics of pseudo-second order, and the adsorption path is well addressed by the Freundlich model both in linear and non-linear form, having an R2 value close to unity. Thermodynamic characteristics point to an exothermic, viable, spontaneous reaction with higher entropy. Utilizing a 1:1 MeOH/H2O ratio, spent adsorbent may be readily regenerated by as much as 75% with a possible three-cycle usage. The practical application of biosorbents was confirmed by real-time effectiveness testing using MB-carrying industrial wastewater, and up to 45.75% adsorption was shown. A relative standard deviation confirmed statistical dependability. All things considered, the current material provides a clean and environmentally friendly way to remove MB dye from various wastewater types.

Tecoma stans floral extract-mediated synthesis of MgFe2O4/ZnO nanoparticles for adsorption and photocatalytic degradation of coomassie brilliant blue dye

Toxic organic dyes-containing wastewater treatment by adsorption and photocatalytic techniques is widely applied, but adsorbents and photocatalysts are often synthesized through chemical methods, leading to secondary pollution by released chemicals. Here, we report a benign method using Tecoma stans floral extract to produce MgFe2O4/ZnO (MGFOZ) nanoparticles for adsorption and photocatalytic degradation of coomassie brilliant blue (CBB) dye. Green MGFOZ owned a surface area of 9.65 m2/g and an average grain size of 54 nm. This bio-based nanomaterial showed higher removal percentage and better recyclability (up to five cycles) than green MgFe2O4 and ZnO nanoparticles. CBB adsorption by MGFOZ was examined by kinetic and isotherm models with better fittings of Bangham and Langmuir or Temkin. RSM-based optimization was conducted to reach an actual adsorption capacity of 147.68 mg/g. Moreover, MGFOZ/visible light system showed a degradation efficiency of 89% CBB dye after 120 min. CBB adsorption can be controlled by both physisorption and chemisorption while •O2- and •OH radicals are responsible for photo-degradation of CBB dye. This study suggested that MGFOZ can be a promising adsorbent and catalyst for removal of organic dyes in water.

Magnetic Fe3O4 nanoparticles loaded guava leaves powder impregnated into calcium alginate hydrogel beads (Fe3O4-GLP@CAB) for efficient removal of methylene blue dye from aqueous environment: Synthesis, characterization, and its adsorption performance

In the present work, a novel Fe3O4-GLP@CAB was successfully synthesized via a co-precipitation procedure and applied for the removal of methylene blue (MB) from aqueous environment. The structural and physicochemical characteristics of the as-prepared materials were explored using a variety of characterization methods, including pHPZC, XRD, VSM, FE-SEM/EDX, BJH/BET, and FTIR. The effects of several experimental factors on the uptake of MB using Fe3O4-GLP@CAB were examined through batch experiments. The highest MB dye removal efficiency of Fe3O4-GLP@CAB was obtained to be 95.2 % at pH 10.0. Adsorption equilibrium isotherm data at different temperatures showed an excellent agreement with the Langmuir model. The adsorption uptake of MB onto Fe3O4-GLP@CAB was determined as 136.7 mg/g at 298 K. The kinetic data were well-fitted by the pseudo-first-order model, indicating that physisorption mainly controlled it. Several thermodynamic variables derived from adsorption data, like as ΔGo, ΔSo, ΔHo, and Ea, accounted for a favourable, spontaneous, exothermic, and physisorption process. Without seeing a substantial decline in adsorptive performance, the Fe3O4-GLP@CAB was employed for five regeneration cycles. Because they can be readily separated from wastewater after treatment, the synthesized Fe3O4-GLP@CAB was thus regarded as a highly recyclable and effective adsorbent for MB dye.

Augmented dye eradication from wastewater using alkali-aided, reinforced waste acacia (Acacia auriculiformis) leaves

The present investigation demonstrates the augmented dye scavenging from wastewater using alkali-mutated acacia (Acacia auriculiformis) leaves powder. The material was synthesized by mild chemical activation by using 0.1 M sodium hydroxide as an activator under room temperature stirring for 3h and isolated as a dark brown powder. The material was characterized using FTIR, FESEM, XRD, and pHzpc; and tested successfully with crystal violet and methylene blue. While FTIR confirms the presence of polyphenolic and polysaccharide moieties, FESEM reveals unprecedented circular hollow pipe-like channels decorated in a highly ordered fashion, facing pores for optimum dye uptake. The adsorption is tunable with working pH, and the maximum adsorption capacities are 67.25 and 78.55 mg g-1 for CV and MB. Both adsorption process follows Langmuir isotherm (R2 = 0.994) and pseudo-2nd-order kinetics (R2 = 0.999). Thermodynamic analysis verifies a spontaneous process with an endothermic interaction beside an elevated degree of randomness. About 80% of the spent material could be regenerated using 1:1 methanol/water. Analysis of industrial effluent suggests 37% removal per cycle, with an operating ceiling of 95%. To wind up, due to huge availability, porous nature, and superior adsorption capacity over other phytosorbents, NaOH-activated acacia leaves could be considered as techno-economic and potential scavengers for sustainable water treatment.

Preparation and Characterization of a Renewable Starch-g-(MA-DETA) Copolymer and Its Adjustment for Dye Removal Applications

Maleic anhydride-diethylenetriamine grafted on starch (st-g-(MA-DETA)) was synthesized through graft copolymerization, and the different parameters (copolymerization temperature, reaction time, concentration of initiator and monomer concentration) affecting starch graft percentage were studied to achieve the maximum grafting percentage. The maximum grafting percentage was found to be 29.17%. The starch and grafted starch copolymer were characterized using XRD, FTIR, SEM, EDS, NMR, and TGA analytical techniques to describe copolymerization. The crystallinity of starch and grafted starch was studied by XRD, confirming that grafted starch has a semicrystalline nature and indicating that the grafting reaction took place typically in the amorphous region of starch. NMR and IR spectroscopic techniques confirmed the successful synthesis of the st-g-(MA-DETA) copolymer. A TGA study revealed that grafting affects the thermal stability of starch. An SEM analysis showed the microparticles are distributed unevenly. Modified starch with the highest grafting ratio was then applied to celestine dye removal from water using different parameters. The experimental results indicated that St-g-(MA-DETA) has excellent dye removal properties in comparison to native starch.

Efficient adsorptive removal of paracetamol and thiazolyl blue from polluted water onto biosynthesized copper oxide nanoparticles

Copper oxide nanoparticles (CuONPs) have received tremendous attention as efficient adsorbents owing to their low cost, desirable surface area, abundant active sites, potent textural characteristics and high adsorption capacities. However, CuONPs have not been employed to decontaminate water laden with increasing environmental contaminants such as thiazolyl blue and paracetamol. Herein, the adsorption of thiazolyl blue and paracetamol onto green synthesized CuONPs prepared from the aqueous leaf extract of Platanus occidentalis was studied. The BET, SEM, FTIR, XRD, EDX and pH point of zero charge showed the successful synthesis of CuONPs having desirable surface properties with a surface area of 58.76 m²/g and an average size of 82.13 nm. The maximum monolayer adsorption capacities of 72.46 mg/g and 64.52 mg/g were obtained for thiazolyl blue and paracetamol, respectively. The Freundlich, pseudo-second-order and intraparticle diffusion models were well fitted to the adsorption of both pollutants. The pH studies suggested the predominance of electrostatic and weaker intermolecular interactions in the adsorption of the thiazolyl blue and paracetamol, respectively. Spontaneous, physical, endothermic and random adsorption of the pollutants on CuONPs was obtained from the thermodynamic consideration. The biosynthesized CuONPs were found to be highly reusable and efficient for the adsorption of thiazolyl blue and paracetamol from water.

Towards a win-win chemistry: extraction of C.I. orange from Kamala fruit (Mallotus philippensis), and simultaneous exercise of its peels for the removal of Methylene Blue from water

Kamala fruit (Mallotus philippensis), hereinafter MP, has been simultaneously exercised for the extraction of a natural dye, C.I. orange and its peels were converted into an efficient adsorbent for the rapid removal of methylene blue (MB) dye from aqueous solutions. The material has been characterized by Fourier Transform Infra-red (FTIR),Field Emission Scanning Electron Microscopy- Electron dispersive spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) surface area, and pH_ZPC. FTIR suggests the presence of polyphenolic moieties responsible for adsorption, whereas FESEM confirms the porous texture. Optimization of process variables such as contact time, pH, adsorbent dose, and temperature of operation indicates that the adsorption gets modulated by the pH, with a best at 11. The Freundlich model (R² = 0.994), and pseudo-second-order kinetics (R² = 0.999) best describe the adsorption pathway. Dilute hydrochloric acid is sufficient to induce >66% regeneration, which ensures reusability. With the maximal uptake for MB is 30.2 mg/g at ambient conditions, the superiority over the existing materials has been confirmed. Treatment of dye containing industrial effluent suggests about a 50% reduction in one cycle. It can be concluded that both-way benefits, namely natural dye extraction and preparation of a peel-based adsorbent for methylene blue removal from aqueous solution, can be achieved using the kamala fruit peels.

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.

Exploring the promising potential of fallen bamboo leaves (Bambusa bambos) for efficient removal of crystal violet from wastewater

Fallen bamboo leaves (Bambusa bambos), hereinafter BL have been designed to be transformed into an efficient and sustainable adsorbent for the removal of crystal violet (CV) dye from wastewater with up to 95% scavenging ability. BL have been characterized by Fourier transform infrared (FTIR) spectra, field emission scanning electron microscopy (FESEM), and zero point charge (pHzpc). The maximum adsorption capacity is 30 mg/g at pH 10. Physico-chemical parameters have been investigated concerning pH, contact time, initial concentration, and coexistent ions. Pseudo-second-order kinetics is followed best (R² =0.999) signifying a chemisorption pathway. Besides, intra-particle diffusion plays a governing role in the film diffusion of crystal violet into the core of the adsorbent. Langmuir isotherm model fits best (R²=0.972) suggesting a uniform, monolayer, and homogeneous adsorption. Regeneration was successful with methanol (65%) and reusability was tested for three cycles and was found to retain activity up to 80%. Analysis of CV containing industrial effluent suggests that a 36.8% reduction is possible with BL. The effect of co-existent ions suggests little influence on the adsorption. Compared to other contemporary and relevant adsorbents, it can be concluded that BL can be exercised for the sustainable decontamination of CV-containing wastewater.

Brinjal (Solanum melongena) stalk waste as an effective scavenger for Eriochrome Black-T from water and wastewater: an approach towards waste to best

Stalks of brinjal (Solanum melongena), hereinafter SM, have been exercised as an efficient and sustainable adsorbent material for the elimination of Eriochrome Black-T (EBT) from an aqueous solution. The material was characterized by FTIR, FESEM, BET surface area, pH_pzc, and proximate analysis. FTIR spectrum suggests the presence of polyphenolic moieties, responsible for successful dye binding. FESEM images show an unprecedented octopus-like texture containing micropores. The central head transforms the architecture of a flower. The evaluated BET surface area of 10.042 m²/g and pore volume 1.055 × 10^-2cm³/g suggest a porous material. The pH_pzc of the material was evaluated to be 7.05, and under optimized conditions, the maximum adsorption capacity was found 52.631 mg/g at pH 7. The operational parameters were studied concerning contact time (0-90 min), pH (5-11), initial concentration (10-40 mg/L), and interfering ions (PO₄^-3, AsO₄^-3, Hg⁺², Pb⁺²). Adsorption follows Langmuir isotherm best (R² = 0.996), and pseudo-second-order kinetics (R² = 0.991) indicate a monolayer and homogeneous adsorption. 83% regeneration was successful with 0.1(M) sodium hydroxide solution. The material can be reused for up to three cycles with 90% efficiency retention. Analysis of EBT containing industrial effluent indicates that 52.62% of EBT can be removed.

Carboxylate-functionalized dragon fruit peel powder as an effective adsorbent for the removal of Rhodamine B (cationic dye) from aqueous solution: adsorption behavior and mechanism

In this study, we used a simple and low-toxicity chemical treatment to make a carboxylate-functionalized dragon fruit peel powder (CF-DFPP) from dragon fruit peel to improve its capacity for adsorbing Rhodamine B (RhB) from an aqueous medium. Field Emission-Scanning Electron Microscopy/Energy-Dispersive X-ray (FE-SEM/EDX), point of zero charges (pH_PZC), Brunauer-Emmett-Teller (BET), and Fourier Transform Infrared (FT-IR) analyses were performed to characterize the adsorbent materials. The adsorption performance and mechanism for the removal of RhB were examined. The kinetic, isotherm and thermodynamic parameters were employed to evaluate the adsorption mechanism. Compared to other models, the Langmuir isotherm and PSO kinetic models better defined the experimental data. CF-DFPP adsorbent exhibited a maximum adsorption efficiency of 228.7 mg/g at 298 K for RhB adsorption. Thermodynamic analysis revealed that the adsorption of RhB by CF-DFPP was spontaneous (ΔG^o < 0) and exothermic (ΔH^o < 0) nature of the process. Different eluting agents were used in desorption tests, and NaOH was revealed to have greater desorption efficiency (96.8%). Furthermore, regeneration examinations revealed that the biosorbent could effectively retain RhB, even after six adsorption/desorption cycles. These findings demonstrated that the CF-DFPP might be a novel material for removing RhB from an aqueous medium.

Biogenic and chemically synthesized Solanum tuberosum peel-silver nanoparticle hybrid for the ultrasonic aided adsorption of bromophenol blue dye

This work was aimed at the synthesis of a hybrid (STpe-AgNP), obtained by impregnation of silver nanoparticles (AgNP) onto Solanum tuberosum peel (STpe), for the ultrasonic assisted adsorption of bromophenol blue (BB) dye. SEM, FTIR, XRD, EDX, TGA and BET techniques were used to characterize the adsorbents. The XRD, SEM and EDX confirmed successful impregnation of AgNPs onto STpe to form the hybrid. The AgNPs impregnated onto the hybrid were found to be water stable at various pH values of 2.0-9.0. Chi-square (χ2 < 0.024) and linear regression (R2 > 0.996) showed that the Freundlich model was best fitted among the isotherm models, corroborated by the oriented site model. Kinetic analysis conformed to the intraparticle diffusion and pseudo-first-order rate equations, while thermodynamics displayed a physical, spontaneous and endothermic adsorption process. The presence of competing Pb(II), Ni(II), Cd(II) and Zn(II) metal ions in solution interfered with the adsorption of BB onto the biosorbents. In terms of reusability, STpe and STpe-AgNP showed BB desorption of 91.3% and 88.5% respectively, using NaOH as eluent. Ultra-sonication significantly enhanced the adsorption of BB by both adsorbents, but the impregnation of AgNPs only slightly improved adsorption of the dye from the simulated wastewater. This study also illustrated that pristine STpe biomass waste is a cheap viable option for the decontamination of BB from water.