Development of high-performance supercapacitor electrode derived from sugar industry spent wash waste

Evaluation of a synbiotic formulation for water remediation in a shrimp pond

In recent years, the use of probiotic bacteria has attracted the interest of the marine shrimp farming industry. However, there are certain limitations pertaining to the practical application of many commercially available probiotics. Here, a thoroughly screened optimal consortium of three indigenous sulfur probiotics was tested for antibiotic susceptibility and was found to be safe, with each culture being sensitive to all the tested antibiotics. Further, de-potash vinasse (DPV), an environmental hazard, was tested for its prebiotic potential, and its 1% (w/v) concentration was found to be effective for long-term viability (> 66 days) of the probiotic cultures and safe for Artemia. The synbiotic formulation was tested first in a lab-scale microcosm setup successfully and subsequently tried on a shrimp farm; it was observed that the product was congruent to the efficiency of a commercial probiotic regarding almost all physicochemical parameters, sulfide, nitrate-N, nitrite-N, phytoplankton sustenance, Pseudomonas count, coliform count, and heterotrophic count. In addition, it was significantly efficient in maintaining pH, reducing ammonia-N and phosphate-P, Vibrio and Aeromonas count, and a net increase in the yield of shrimp biomass by 625 kg, thus proving to be a better alternative than one of the already available remediation methods.

Treatment technologies for bakers' yeast production wastewater

Researchers in recent years have utilized a broad spectrum of treatment technologies in treating bakers' yeast production wastewater. This paper aims to review the treatment technologies for the wastewater, compare the process technologies, discuss recent innovations, and propose future perspectives in the research area. The review observed that nanofiltration was the most effective membrane process for the treatment of the effluent (at >95% pollutant rejection). Other separation processes like adsorption and distillation had technical challenges of desorption, a poor fit for high pollutant load and cost limitations. Chemical treatment processes have varying levels of success but they are expensive and produce toxic sludge. Sludge production would be a hurdle when product recovery and reuse are targeted. It is difficult to make an outright choice of the best process for treating the effluent because each has its merits and demerits and an appropriate choice can be made when all factors are duly considered. The process intensification of the industrial-scale production of the bakers' yeast process will be a very direct approach, where the process optimisation, zero effluent discharge, and enhanced recovery of value-added product from the waste streams are important approaches that need to be taken into account.

Enhancing arsenic sequestration on ameliorated waste molasses nanoadsorbents using response surface methodology and machine-learning frameworks

The development of a novel nanobiosorbent derived from waste molasses for the adsorptive removal of arsenic (As) has been attempted in this study. Waste molasses were chemically ameliorated through a solvothermal route for the incorporation of iron oxide, thereby producing iron oxide incorporated carbonaceous nanomaterial (IOCN). Synthesis of IOCN was confirmed through transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and atomic emission spectroscopy (AES) analysis. The surface area and porous behavior of IOCN were elucidated by Brunauer-Emmett-Teller (BET) assessments. The experimental conditions for adsorption were first modeled using response surface methodology (RSM) based on the central composite design (CCD), considering the parameters: adsorbate dosage, adsorbent dosage, pH, and contact time. RSM optimizations were improved upon using a three-layer feed-forward multilayer perceptron (MLP) based Artificial Neural Network (ANN) model. Optimization through ANN model resulted in the increase of the maximal As adsorption efficiency to ~ 96% for IOCN. The IOCN isotherm plots show the best fit for the Sips isotherm, and the reaction kinetics follows the pseudo-second-order model, indicating the chemisorption mechanism for As adsorption. Evidence for direct coordination of As to the surface of adsorbents was further confirmed by FTIR spectroscopic studies before and after As adsorption. The high adsorption efficiencies and the low-cost facile synthesis of the IOCN nanosorbent from agro-industrial waste indicate their potential for commercial applications.

3D N,O-Codoped Egg-Box-Like Carbons with Tuned Channels for High Areal Capacitance Supercapacitors

Functional carbonaceous materials for supercapacitors (SCs) without using acid for post-treatment remain a substantial challenge. In this paper, we present a less harmful strategy for preparing three-dimensional (3D) N,O-codoped egg-box-like carbons (EBCs). The as-prepared EBCs with opened pores provide plentiful channels for ion fast transport, ensure the effective contact of EBCs electrodes and electrolytes, and enhance the electron conduction. The nitrogen and oxygen atoms doped in EBCs improve the surface wettability of EBC electrodes and provide the pseudocapacitance. Consequently, the EBCs display a prominent areal capacitance of 39.8 μF cm-2 (340 F g-1) at 0.106 mA cm-2 in 6 M KOH electrolyte. The EBC-based symmetric SC manifests a high areal capacitance to 27.6 μF cm-2 (236 F g-1) at 0.1075 mA cm-2, a good rate capability of 18.8 μF cm-2 (160 F g-1) at 215 mA cm-2 and a long-term cycle stability with only 1.9% decay after 50,000 cycles in aqueous electrolyte. Impressively, even in all-solid-state SC, EBC electrode shows a high areal capacitance of 25.0 μF cm-2 (214 F g-1) and energy density of 0.0233 mWh cm-2. This work provides an acid-free process to prepare electrode materials from industrial by-products for advanced energy storage devices.

Ferrous metal-organic frameworks with stronger coordinatively unsaturated metal sites for persulfate activation to effectively degrade dibutyl phthalate in wastewater

In the advanced oxidation system (AOPs) of persulfate (PS) activated by iron-based metal-organic frameworks (MOFs), aim at solving the problem on the treatment difficulty of wastewater with low concentration persistent organic pollutants (POPs), a new type of ferrous metal-organic frameworks (Fe(Ⅱ)-MOFs) with stronger coordinatively unsaturated metal sites (CUS) was successfully synthesized by different methods. The catalytic performance of Fe(Ⅱ)-MOFs was were obtained by the experiment of degrading dibutyl phthalate (DBP) through persulfate activation. It was found that the degradation efficiency of 0.018 mmol L^-1 DBP was 86.73% under the conditions of 0.40 g L^-1 and 2.70 mmol L^-1 persulfate at a wide pH range. At the same time, the crystal structure and surface morphology of Fe(Ⅱ)-MOFs did not change significantly after reaction and it could still maintain the removal rate of 75.44% of the target pollutants in the fifth cycle. Furthermore, in the consideration of iron valence state of MOFs before and after reaction, and combined with the analysis of electrochemical properties, the possible mechanism of PS activation was proposed, namely the metastable electron layer inside ferrous ions produced the internal power to accelerate the electron transfer in CUS, leading to improve the activity of the catalyst.

Supercapacitor Energy Storage Device Using Biowastes: A Sustainable Approach to Green Energy

The demand for renewable energy sources worldwide has gained tremendous research attention over the past decades. Technologies such as wind and solar have been widely researched and reported in the literature. However, economical use of these technologies has not been widespread due partly to cost and the inability for service during of-source periods. To make these technologies more competitive, research into energy storage systems has intensified over the last few decades. The idea is to devise an energy storage system that allows for storage of electricity during lean hours at a relatively cheaper value and delivery later. Energy storage and delivery technologies such as supercapacitors can store and deliver energy at a very fast rate, offering high current in a short duration. The past decade has witnessed a rapid growth in research and development in supercapacitor technology. Several electrochemical properties of the electrode material and electrolyte have been reported in the literature. Supercapacitor electrode materials such as carbon and carbon-based materials have received increasing attention because of their high specific surface area, good electrical conductivity and excellent stability in harsh environments etc. In recent years, there has been an increasing interest in biomass-derived activated carbons as an electrode material for supercapacitor applications. The development of an alternative supercapacitor electrode material from biowaste serves two main purposes: (1) It helps with waste disposal; converting waste to a useful product, and (2) it provides an economic argument for the substantiality of supercapacitor technology. This article reviews recent developments in carbon and carbon-based materials derived from biowaste for supercapacitor technology. A comparison between the various storage mechanisms and electrochemical performance of electrodes derived from biowaste is presented.

Synthesis of high surface area porous carbon from anaerobic digestate and it's electrochemical study as an electrode material for ultracapacitors

The remnants of the anaerobic digestion process, ‘the digestate,’ mainly consist of fibrous lignin and cellulose like molecules, as a significant carbon repository along with some other inorganic impurities. The present work demonstrates the potential use of anaerobically treated fruit and vegetable waste (FVW) as a source of porous carbon for supercapacitor electrode materials. This work suggests that the FVW digestate can inherit silicon (Si) and calcium (Ca) based inorganic impurities, which play an essential role as structure directing agents for digestate derived carbon. These contaminants act as hard templates during carbonization to create hierarchical pores and contribute to an enhancement in surface area. Different batches from an anaerobic biogas digester plant are converted to porous carbon and examined as a potential supercapacitor electrode material. A maximum capacitance of 235 F g⁻¹ is achieved from DDHPC-4kh carbon with a specific surface area of 2502 m² g⁻¹ at a current density of 1 A g⁻¹ in an acidic aqueous electrolyte. The results are significant in comparison to other bio-sourced precursors studied previously.

The remnants of the anaerobic digestion process, ‘the digestate,’ mainly consist of fibrous lignin and cellulose like molecules, as a significant carbon repository along with some other inorganic impurities.

One-step preparation of N,O co-doped 3D hierarchically porous carbon derived from soybean dregs for high-performance supercapacitors

Hierarchically porous carbon (HPC) material based on environmental friendliness biomass has spurred much attention, due to its high surface area and porous structure. Herein, three-dimensional (3D) N,O co-doped HPC (N–O-HPC) was prepared by using a one-step fabrication process of simultaneously carbonizing and activating soybean dregs and used as an electrode for supercapacitors (SCs). The obtained N–O-HPC with 4.8 at% N and 6.1 at% O exhibits a pretty small charge transfer resistance (0.05 Ω) and a large specific capacitance (408 F g⁻¹ at 1 A g⁻¹), due to its 3D hierarchically porous framework structure with extremely large specific surface area (1688 m² g⁻¹). Moreover, a symmetrical SC assembled with the HPC electrode exhibits an amazingly high energy density (22 W h kg⁻¹ at 450 W kg⁻¹) and a stable long cycling life with only 6% capacitance loss after 5000 cycles in 1 M Na₂SO₄ solution. This work provides a facile, green, and low-cost way to prepare electrode materials for SCs.

N,O co-doped 3D HPC derived from soybean dregs was prepared by a one-step method and displays an amazingly high energy density of 22 W h kg⁻¹ (450 W kg⁻¹) using 1 M Na₂SO₄ solution.

Solvent-free production of nano-FeS anchored graphene from Ulva fasciata: A scalable synthesis of super-adsorbent for lead, chromium and dyes

Here we demonstrate, a simple and solvent-free synthetic route for the production of FeS/Fe(0) functionalized graphene nanocomposite (G-Fe) via a one-step pyrolysis of seaweed biomass (Ulva fasciata). It is proposed that the natural abundance of both inorganic and organic sulfur in the seaweed induces the reduction of exfoliated graphitic sheets at elevated temperatures. FeCl₃ was employed both as the iron precursor as well as the templating agent. Iron doping played a dual-faceted role of exfoliating as well as activating agent, producing composite with high adsorption capacity for Pb²⁺ (645 ± 10 mg/g), CR (970 mg/g), CV(909 mg/g), MO (664 mg/g), MB (402 mg/g) dyes and good recyclability (8 cycles). Pb²⁺ adsorption was irreversible even at low pH values and the spent composite (G-Fe-Pb) was utilized for efficient Cr(IV) removal (̴100 mg/g). The adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. Further, a thin layer of composite was deposited on a filter paper by vacuum filtration which was tested under continuous filtration mode for RB5 dye removal. Preliminary results highlight the potential of this composite to be used in pretreatment steps in hybrid membrane processes for filtration of complex wastewater feeds.