Development of Newer Adsorbents: Activated Carbons Derived from Carbonized Cassia fistula

Towards enhancement of fungal hydrolytic enzyme cocktail using waste algal biomass of Oscillatoria obscura and enzyme stability investigation under the influence of iron oxide nanoparticles

Development of low-cost and economic cellulase production is among the key challenges due to its broad industrial applications. One of the main topics of research pertaining to sustainable biomass waste based biorefinaries is the development of economic cellulase production strategies. The main cause of the increase in cellulase production costs is the use of commercial substrates; as a result, the cost of any cellulase-based bioprocess can be decreased by employing a productive, low-cost substrate. The goal of the current study is to develop low-cost cellulase using the carbohydrate-rich, renewable, and widely accessible cyanobacteria algae Oscillatoria obscura as the production substrate. Maximum cellulase was produced utilising the fungus Rhizopus oryzae at substrate concentration of 7.0 g among various tested concentrations of algal biomass. Maximum production rates of 22 IU/gds FP, 105 IU/gds BGL, and 116 IU/gds EG in 72 h were possible under optimal conditions and substrate concentration. Further investigations on the crude enzyme's stability in the presence of iron oxide nanoparticles (IONPs) revealed that it was thermally stable at 60 °C for up to 8 h. Additionally, the crude enzyme demonstrated pH stability by maintaining its complete activity at pH 6.0 for 8 h in the presence of the optimal dose of 15 mg IONPs. The outcomes of this research may be used to investigate the possibility of producing such enzymes in large quantities at low cost for industrial use.

Green Preparation of Robust Hydrophobic β-Cyclodextrin/Chitosan Sponges for Efficient Removal of Oil from Water

A relatively straightforward green method to fabricate robust hydrophobic sponges for effective removal of oil pollutants and other organic contaminants was developed. These sponges were constructed from bio-sources: citronellal and palmitic acid-modified aminoethyl cyclodextrin-sodium phytate-chitosan (ACCTCS). The modified sponge exhibited desirable mechanical properties and strong hydrophobicity with a water contact angle (WCA) of 147.8°. Scanning electron microscopy showed that the ACCTCS sponge had a highly porous structure that was particularly suitable for organic component absorption. The sponge exhibited excellent absorption capacities for n-hexane, trichloromethane, vacuum pump oil, and peanut oil (47.9, 32.3, 32.6, and 32.2 g/g, respectively). The removal rate of oil was more than 80% (>26.2 g/g) after 10 absorption-desorption cycles. The ACCTCS sponge also showed good oil/water and organic components/water separation performance. The bio-source materials, green preparation method, and new absorbed-oil recovery strategy provided a novel pathway to construct multifunctional absorbents for oil/water separation in industrial wastewater.

Activated carbons from waste Cassia bakeriana seed pods as high-performance adsorbents for toxic anionic dye and ciprofloxacin antibiotic remediation

Waste Cassia bakeriana seed pods were used for porous carbon production in a facile pyrolysis process. The carbons were highly efficient adsorbents for methylene blue, congo red and ciprofloxacin antibiotic from aqueous media. The experimental results demonstrated that despite moderate surface area of 283.4 m²/g, KOH activated carbon (PSAC-KOH) exhibited the highest adsorption capacity for congo red reported to date for carbon-based adsorbents (970 mg/g). PSAC-KOH also demonstrated a high adsorption capacity at 600 mg/g for ciprofloxacin. Raman spectroscopy, X-ray diffraction and X-ray Photoelectron spectroscopy analysis of the carbons demonstrated an extensive graphitic characteristic, while Fourier transform infrared spectra of PSAC-KOH suggested a high proportion of aromaticity which promotes adsorption mechanisms including electrostatic and π-π interactions. Pseudo-second-order kinetic model fitting suggested a rate-controlling chemisorption mechanism. The utilization of waste Cassia bakeriana seed pods for carbon production may create new opportunities to develop sustainable and highly efficient adsorbents for water remediation.

Java plum and amaltash seed biomass based bio-adsorbents for synthetic wastewater treatment

Biomass of Java plum (JP) and amaltash (AT) seeds were employed to remove arsenic from synthetic wastewater, cost effectively. The prepared biomasses were characterized by FE-SEM, EDX, FTIR, XRD, and ICP techniques. Experimentation the optimization study has been carried out by using Design-software 6.0.8. Response surface methodology has been applied to design the experiments where we have used three factors and three levels Box-Behnken design (BBD). Arsenic removal ability of bio-sorbents was evaluated and optimized by varying pH, adsorbent dose concentration of arsenic in synthetic wastewater. For 2.5 mg/L arsenic concentration and 80 mg adsorbent dose at pH 8.8 Java plum seeds (JP) based bio-adsorbent removed ∼93% and amaltash seeds (AT) based bio-adsorbent removed ∼91% arsenic from synthetic wastewater. The adsorption behaviour better explained following Freundlich model (R² = 0.99) compared to Temkin model (R² = 0.986) for As (III) ions. The adsorption capacity was 1.45 mg g^-1 and 1.42 mg g^-1 for JP and AT, respectively after 80 min under optimal set of condition. The adsorption kinetics was explained by either pseudo-first order model or Elovich model.

Desulfurization studies of liquid fuels through nickel-modified porous materials from Pongamia pinnata

Abstract

A new biomass-based carbonaceous adsorbent has been developed from Pongamia pinnata and its effect upon nickel modification- and adsorption-coupled ultrasonication was investigated. Adsorption experiment of the model oil constituting 50 ppm dibenzothiophene in cyclohexane showed the maximum capacity as 8.11, 13.36, and 17.15 mg·g−1 for the commercial carbon DARCO, virgin bio-adsorbent PP, and nickel-modified adsorbent Ni@PP, respectively, with the time required for attaining equilibrium being the fastest in Ni@PP (120 min). The significant effect of ultrasonication was in attaining faster kinetics where ~ 96–98% removal was achieved in only 30 min. Also, the developed adsorbents had a very good specific surface area of 915 and 677 m2·g−1, respectively, for PP and Ni@PP. Investigation of the effect of higher initial sulfur concentration (200 ppm) indicated the significance of Ni modification, where a very high capacity of 66.18 mg·g−1 for Ni@PP was attained against 30.90 mg·g−1 for PP and 13.18 mg·g−1 for DARCO. Ni@ PP was also effective for the simultaneous removal of more refractory sulfur fractions from multicomponent model fuel systems and exhibited good regeneration ability till the fourth cycles or more. Cost estimation showed that the developed adsorbents are relatively ten times cheaper than commercial carbon, while the fixed-bed study indicated a breakthrough time of 250 min and 270 min for PP and Ni@PP, respectively.

Graphic abstract

Study on the performance and mechanism of aerobic oxidative desulfurization based on a dual-functional material possessing catalytic and adsorptive properties

Herein, three polyoxometalates, namely K₃PW₁₂O₄₀·10H₂O, K₆[α-P₂W₁₈O₆₂]·14H₂O, and K₈H[P₂W₁₅V₃O₆₂]·9H₂O, were successfully prepared and used in the air/n-octanaloxidative desulfurization (ODS) system.

Elucidating efficacy of biomass derived nanocomposites in water and wastewater treatment

In the present study, two synthesis methods of nanocomposites-one involving a mixture of biomass and the other using chemical modification were investigated to evaluate practical application of green approach in pollution control, specifically for water and wastewater treatment. Newer multifunctional superparamagnetic nanocomposites using biomaterials such as unripened fruit of Cassia fistula (Golden shower) and Aloe vera were developed as an example of green approach while chemical modification was illustrated using n-octanol. Two specific model applications were studied for the developed materials-dye removal (Methyl Blue and Congo Red) and disinfection-demonstrating antimicrobial property. To elucidate the multifunctional character, the texture, morphology and composition of the prepared bionanocomposites were studied. The surface area values were 6.2 and 9.8 m²/g for Aloe vera and octanol based nanocomposites while the average pore diameters were 1.79 nm and 5.7 nm respectively, indicating presence of highly developed micropores in the first material having a honeycomb shape and the later showing excellent staircase type formation with larger pores. A very high dye removal to the extent of 100% was obtained that can be attributed largely to the functionalities imparted from Cassia fistula compared to ingredients from Aloe vera and octanol. The nanomaterials could be completely separated with absolute ease by applying simple magnetic field. Also, successful application of the developed materials in disinfection, removal of E. coli, was demonstrated with a very high efficiency of over 95%. The biomass derived nanocomposites exhibit excellent pollutant removal and disinfection properties, even at very low nanoparticle content; octanol based material indicating ∼5 times lowered cost, while the Aloe vera based bionanocomposites have potential for cost reduction to the extent of 10 times as compared to only magnetite nanoparticles, thereby highlighting techno-economical alternative in water and wastewater treatment.

Fast and efficient adsorption of methylene green 5 on activated carbon prepared from new chemical activation method

Activated carbon (AC) was synthesized from golden shower (GS) through a new chemical activation process. The three-stage process comprised (1) hydrothermal carbonization of GS to produce hydrochar, (2) pyrolysis of hydrochar to produce biochar, and (3) subsequent chemical activation of biochar with K₂CO₃ to obtain GSHBAC. The traditional synthesis processes (i.e., one-stage and two-stage) were also examined for comparison. In the one-stage process, GS that was impregnated with K₂CO₃ was directly pyrolyzed (GSAC), and the two-stage process consisted of (1) pyrolytic or hydrothermal carbonization to produce biochar or hydrochar and (2) subsequent chemical activation was defined as GSBAC and GSHAC, respectively. The synthesized ACs were characterized by scanning electron microscope, Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectrometry, point zero charge, and Boehm titration. The adsorption results demonstrated that the MG5 adsorption process was not remarkably affected by neither the solution pH (2.0-10) nor ionic strength (0-0.5 M NaCl). Kinetic studies showed that the adsorption equilibrium was quickly established, with a low activation energy required for adsorption (Ea; 3.30-27.8 kJ/mol), and the ACs removed 50-73% of the MG5 concentration from solution within 01 min. Desorption studies confirmed the adsorption was irreversible. Thermodynamic experiments suggested that the MG5 adsorption was spontaneous (-ΔG°) and endothermic (+ΔH°), and increased the randomness (+ΔS°) in the system. Although the specific surface areas of the ACs followed the order GSAC (1,413) > GSHAC (1,238) > GSHBAC (903) > GSBAC (812 m²/g), the maximum adsorption capacities determined from the Langmuir model (Q^o_max) at 30 °C exhibited the following order: GSHBAC (531) > GSAC (344) > GSHAC (332) > GSBAC (253 mg/g). Oxygenation of the ACs' surface through a hydrothermal process with acrylic acid resulted in a decrease in MG5 adsorption and identified the importance of π-π interactions to the adsorption process. The primary interactions in MG5 adsorption were π-π interactions and pore filling, while hydrogen bonding and n-π interactions were minor contributors. The three-stage process can be regarded as the effective preparation method of AC with a high adsorption capacity toward the cationic dye.

New Composites LnBDC@AC and CB[6]@AC: From Design toward Selective Adsorption of Methylene Blue or Methyl Orange

New porous composites LnBDC@AC (AC = Activated carbon, Ln = Eu and Gd and BDC = 1,4-benzenedicaboxylate) and CB[6]@AC (CB[6] = Cucurbit[6]uril) were obtained using hydrothermal route. The LnBDC and CB[B] are located inside the pore of the carbon materials as was observed in SEM-EDS, XRPD and FT-IR analysis. Porosimetry analysis showed values typically between AC and LnBDC material, with pore size and surface area, respectively, 29,56 Å and 353.98 m²g^-1 for LnBDC@AC and 35,53 Å and 353.98 m²g^-1 for CB[6]@AC. Both materials showed good absorptive capacity of metil orange (MO) and methylene blue (MB) with selectivity as a function of pH. For acid pH, both materials present selectivity by MB and alkaline pH for MO, with notable performance for CB[6]@AC. Additionally, europium luminescence was used as structural probe to investigate the coordination environment of Eu³⁺ ions in the EuBDC@AC composite after adsorption experiment.

Functionalization of Petroleum Coke-Derived Carbon for Synergistically Enhanced Capacitive Performance

Petroleum coke is a valuable and potential source for clean energy storage if it could be modified legitimately and facilely. In the present study, porous carbon with high surface area and abundant oxygen-containing groups was prepared from petroleum coke by chemical activation and modification processes. The as-prepared carbon exhibits a high surface area (1129 m(2) · g(-1)) and stable micrographic structure. It presents a high specific capacitance and excellent rate performance in KOH electrolyte. Even at an ultrahigh current density of 50 A · g(-1), the specific capacitance of the prepared carbon can still reach up to an unprecedented value of 261 F · g(-1) with a superhigh retention rate of 81 %. In addition, the energy density of this material in aqueous electrolyte can be as high as 13.9 Wh · kg(-1). The high energy density and excellent rate performance ensure its prosperous application in high-power energy storage system.