Biogas production from malt bagasse from craft beer industry: kinetic modeling and process simulation.

In this work, biogas was synthesized from malt enriched-craft beer bagasse with the objective to generate clean energy. Thus, a kinetic model based on thermodynamic parameters was proposed to represent the process with coefficient determination (R2) of 0.82. A bench-top biodigester of 2.0 × 10-3 m3 was built in glass, and equipped with sensors to measure pressure, temperature, and methane concentration. The inoculum selected for the anaerobic digestion was the granular sludge, and malt bagasse was used as substrate. Data were fitted to a pseudo-first-order model for the formation of methane gas using the Arrehnius equation as basis. For the simulations of biogas production, the Aspen Plus™ software was used. Results from 23 factorial design experiments evidenced that equipment was efficient, and the craft beer bagasse showed great biogas production, with nearly 95% of methane yield. The temperature was the variable that showed most influence in the process. Moreover, the system has a potential for the generation of 10.1 kWh of clean energy. Kinetic constant rate for methane production was 5.42 × 10-7 s-1 and activation energy 8.25 kJ mol-1. A statistical analysis using a math software was performed and evidenced that the temperature played a major role in the biomethane conversion. Supplementary Information: The online version contains supplementary material available at 10.1007/s10163-023-01715-7.

Removal of textile dyes by benefited marine shells wastes: From circular economy to multi-phenomenological modeling.

Marine shell wastes were thermally activated and characterized as aragonite and calcite phases and were used in the removal of synthetic anionic dyes, Bright Blue Acid (NB180) and Reactive Red 133 (RR133). Benefited marine shells were classified as low-cost (USD 0.33/g of adsorbent) in comparison with other reported materials. Furthermore, the absence of chemicals in the adsorbent preparation allows its further employment in economic activities. The coexistence of adsorption and exchange-precipitation reaction was responsible for up to 93% of dye removal, whilst the maximum adsorption capacities were 225 mg g-1 for NB180 and 36 mg g-1 for RR133. The observed kinetic behavior of the dye removal by the adsorbent allowed the proposal of a mechanism for dye-adsorbent interaction in liquid-solid interface considering both adsorption and exchange-precipitation reaction. Contribution of the exchange-precipitation reaction in the removal process was quantified as being approximately 75% for NB180 and 25% for RR133. The mathematical model that phenomenologically described the kinetic behavior of the dye removals gave the magnitude order of the kinetic parameters as kads = 8.67-9.49 min-1 and kp = 1.18-2.84 min-1, due to the adsorption and the (exchange-reaction)-precipitation, respectively. This work indicates the step (exchange reaction)-precipitation as an additional contribution to improve the dye removal from aqueous effluents, achieving in the evolution of the process up to 24% in terms of kinetic selectivity of removal.

Adsorptive and photocatalytic activity of Fe3O4-functionalized multilayer graphene oxide in the treatment of industrial textile wastewater.

Multilayer graphene oxide (mGO) was synthesized and functionalized via co-precipitation method to produce magnetic Fe3O4-functionalized multilayer graphene oxide nanocomposite (MmGO). Photocatalytic properties of MmGO were investigated in the photodegradation of raw textile wastewater samples. Fourier-transformed infrared spectroscopy revealed Fe-O vibrations, characterized by the band shift from 636.27 to 587.25 cm-1 on MmGO. X-ray diffraction confirmed the successful oxidation of graphite by the (002) peak at 10° and indicated the presence of Fe3O4 on MmGO surface by the peaks at 2θ 35.8° (311), 42.71° (400), 54.09° (511), and 62.8° (440). There was no detection of coercivity field and remnant magnetization, evidencing a material with superparamagnetic properties. Then, the textile effluent was treated by heterogeneous photo-Fenton (HPF) reaction. A 22 factorial design was conducted to evaluate the effects of MmGO dosage and H2O2 concentration on HPF, with color and turbidity removal as response variables. The kinetic behavior of the adsorption and HPF processes was investigated separately, in which, the equilibrium was reached within 60 and 120 min, for adsorption and HPF, respectively. Pseudo-second-order model exhibited the best fit, with COD uptake capacity at equilibrium of 4094.94 mg g-1, for chemical oxygen demand. The modeling of kinetics data showed that the Chan and Chu model was the most representative for HPF, with initial removal rate of 95.52 min-1. The removal of organic matter was 76.36% greater than that reached by conventional treatment at textile mills. The presence of Fe3O4 nanoparticles attached to MmGO surface was responsible for the increase of electron mobility and the enhancement of its photocatalytic properties. Finally, MmGO presented low phytotoxic to Cucumis sativus L. with a RGI of 0.53. These results bring satisfactory perspectives regarding further employment, on large scale, of MmGO as nanocatalyst of textile pollutants.

In-depth investigation of Sodium percarbonate as oxidant of PAHs from soil contaminated with diesel oil.

Sodium percarbonate (SPC, 2Na2CO3∙3H2O2), is a compound that can be used under multiple environmental applications. In this work, SPC was employed as oxidant in the treatment of soil contaminated with diesel oil. The soil samples were collected during the earthmoving stage of RNEST Oil Refinery (Petrobras), Brazil. Then, the samples were air-dried, mixed and characterized. Subsequently, raw soil was contaminated with diesel and treated by photo-Fenton reaction (H2O2/Fe2+/UV). SPC played a significant role in the generation of hydroxyl radicals under the catalytic effect of ferrous ions (Fe2+), hydrogen peroxide (H2O2) and radiation. These radicals provoked the photodegradation of polycyclic aromatic hydrocarbons (PAHs), in the soil remediation. A factorial design 33 was carried out to assess the variables which most influenced the decrease in total organic carbon (TOC). The study was performed with the following variables: initial concentration of [H2O2] and [Fe2+], between 190.0 and 950.0 mmol L-1 and 0.0-14.4 mmol L-1, respectively. UV radiation was supplied from sunlight, blacklight lamps, and system without radiation. All experiments were performed with 5.0 g of contaminated soil in 50.0 mL of solution. The initial concentration of Fe2+ showed the statistically most significant effect. The oxidation efficiency evaluated in the best condition showed a decrease from 34,765 mg kg-1 to 15,801 mg kg-1 in TOC and from 85.750 mg kg-1 to 20.770 mg kg-1 in PAHs content. Moreover, the sums of low and high molecular weight polycyclic aromatic hydrocarbons (LMW-PAHs and HMW-PAHs) were 19.537 mg kg-1 and 1.233 mg kg-1, respectively. Both values are within the limits recommended by the United Sates Environmental Protection Agency (USEPA) and evidenced the satisfactory removal of PAHs from contaminated soil, being an alternative to classic oxidation protocols.

One step forward: How can functionalization enhance the adsorptive properties of graphene towards metallic ions and dyes?

Functionalized graphene and its derivatives have been subject of many recent studies investigating their use as scavenger of various industrial pollutants. Adsorption is a feasible treatment, which can employ a wide variety of materials as adsorbents. Additionally, graphene has been distinguished for its remarkable properties, such as mechanical resistance, flexibility and electric conductivity. A relevant aspect of functionalized graphene is related to its selectivity, resulting in increased removal rates of specific pollutants. Hence, the functionalization process of graphene nanosheets is the cutting edge of the materials and environmental sciences, promoting the development of innovative and highly capable sorbents. The purpose of this review is to assemble the available information about functionalized graphene nanomaterials used for the removal of water pollutants and to explore its wide potential. In addition, various optimal experimental conditions (solution pH, equilibrium time, adsorbent dosage) are discussed. In each topic, aspects of environmental protection of adsorption process were evaluated, as well as the most recent works, available from high impact journals in the field, have been explored. Additionally, the employment of natural compounds to functionalize, reduce and support graphene, was evaluated as green alternatives to chemicals.

Amino-Fe3O4-functionalized multi-layered graphene oxide as an ecofriendly and highly effective nanoscavenger of the reactive drimaren red.

Amino-functionalized multilayer graphene oxide (Am-nGO) has been synthesized and applied to remove the reactive drimaren red (DR) from aqueous solutions. Infrared spectroscopy evidenced amine and amide presence by peaks at 1579 cm-1 and a band between 3300 and 3500 cm-1. Raman spectroscopy showed an increment in ID/IG ratio after amino-Fe3O4-functionalization of nGO from 1.05 to 1.20, referent to an increase in sp3 domain disorder. The isoelectric point of Am-nGO was pH 8.1. From kinetic study, the equilibrium was achieved within 90 min; moreover, pseudo-n-order model satisfactorily fitted to the experimental data. Kinetic constant (kn) was 0.71 mg1-n g1-n min-1 and modeled equilibrium sorption capacity (qe) 219.17 mg g-1. Equilibrium experiments showed monolayer adsorption capacity (qm) of 219.75 mg g-1, and BET model best fitted to the equilibrium data, indicating that the adsorption process happened with multiple layers formation. From sorption thermodynamics, the standard free energy of Gibbs and enthalpy were respectively - 31.91 kJ mol-1 (at 298 K) and 66.43 kJ mol-1. Such data evidence the spontaneous and chemical behavior of DR adsorption as a consequence of strong electron donor-receptor interactions between the dye and the nanosorbent. By phytotoxicity assessment, Am-nGO showed inexpressive inhibitory potential to American lettuce seeds in comparison with its precursor nGO and graphite nanoplatelets.

Treated residue from aluminium lamination as adsorbent of toxic reactive dyes - a kinetic, equilibrium and thermodynamic study.

The residue generated in the aluminium cold lamination (TTR) was submitted to a direct burning and then it was calcined at 500°C. BET, FTIR, SEM with EDX and TGA techniques were performed to characterize the adsorbent before and after the adsorption. BET analysis showed that TTR specific surface area was 55.37 m2 g-1 and there were no significant changes after the adsorptive process. Afterwards, the TTR was applied as adsorbent of the reactive Drimaren Blue (DB), Drimaren Red (DR) and Drimaren Gold (DG). Its employment consists in a sustainable alternative for the treatment of textile wastewater, once the TTR was used as low-cost adsorbent of textile dyes. Kinetic studies showed that the process reached the equilibrium state between 5 and 10 min. The pseudo-second-order model better fitted the adsorption kinetics, with kinetic rate constants 10.51, 34.71 and 31.51 mg min g-1 for DB, DR and DG respectively. The equilibrium experiments were performed to obtain the adsorption parameters for each dye; moreover, the maximum adsorption capacity was 6.27, 0.42 and 1.23 mg g-1 for DB, DR and DG, respectively. Thermodynamics studies allowed to obtain the values of enthalpy for DB, DR and DG, -7.90, 14.03 and -17.75 kJ mol-1, respectively. Furthermore, the negative values of Gibbs free energy confirmed the spontaneity of the adsorption. The results point to the physisorption characteristic of the process, in which the temperature negatively influenced the adsorption for the DB and DG; the opposite result was observed for the DR.

Amino-Fe3O4-functionalized graphene oxide as a novel adsorbent of Methylene Blue: kinetics, equilibrium, and recyclability aspects.

Graphene oxide (GO) was synthetized from graphite oxidation via the modified Hummers method. Afterwards, the GO was functionalized with diethylenetriamine (DETA) and FeCl3 to obtain the novel amino-iron oxide functionalized graphene (GO-NH2-Fe3O4). FTIR, XRD, SEM with EDX, and Raman spectroscopy were performed to characterize both GO and GO-NH2-Fe3O4. The GO-NH2-Fe3O4 was then evaluated as adsorbent of the cationic dye Methylene Blue (MB); analysis of the point of zero net charge (pHPZC) and pH effect showed that the GO-NH2-Fe3O4 pHPZC was 8.2; hence, the MB adsorption was higher at pH 12.0. Adsorption kinetics studies indicated that the system reached the equilibrium state after 5 min, with adsorption capacity at equilibrium (qe) and kinetic constant (kS) of 966.39 mg g-1 and 3.17∙10-2 g mg-1 min-1, respectively; moreover, the pseudo-second-order model was better fitted to the experimental data. Equilibrium studies showed maximum adsorption capacity of 1047.81 mg g-1; furthermore, Langmuir isotherm better fitted the adsorption. Recycling experiments showed that the GO-NH2-Fe3O4 maintained the MB removal rate above 95% after 10 cycles. All the results showed sorbent high adsorption capacity and outstanding regeneration capability and evidenced the employment of novel GO-NH2-Fe3O4 as a profitable adsorbent of textile dyes.

Anomalocardia brasiliana shellfish shells as a novel and ecofriendly adsorbent of Nylosan Brilliant Blue acid dye.

Malacoculture waste (Anomalocardia brasiliana) shellfish shells (ABSS) were evaluated as adsorbents of Nylosan Brilliant Blue (NBB) acid dye. The ABSS were thermally activated at 1,000 °C for 10 h and then characterized by Fourier-transform infrared spectroscopy, analysis of specific surface area (BET), X-ray diffraction (XRD), and scanning electron microscopy. Point of zero charge (PZC) analysis of ABSS verified pHPZC 13.0. The study of kinetics showed that the pseudo-second-order model fit the experimental data best and the system reached equilibrium within 5 min. Adsorption isotherms followed the Langmuir-Freundlich isotherm and ABSS reached an outstanding maximum adsorption capacity of 405 mg·g-1 under the following optimum conditions: pH 12.4, 303 K, 450 rpm, 2.0 g of adsorbent, and 150 µm average particle size. These conditions were obtained after a previous statistical analysis of the variables. Enthalpy and Gibbs energy obtained in the thermodynamics experiments were -23.79 kJ·mol-1 and -4.07 kJ·mol-1, respectively. These parameters confirm that the process is exothermic, spontaneous, and indicative of the physical nature of the adsorption. The adsorption of NBB onto ABSS tended to be more favorable at a lower temperature. Low value of enthalpy suggested that weak binding forces, such as electrostatic interactions, govern the sorption mechanism. ABSS high availability in the environment, its low toxicity and high efficiency make it a promising ecofriendly adsorbent of textile dyes.