Carbon from Bagasse Activated with Water Vapor and Its Adsorption Performance for Methylene Blue

Cellulose de-polymerization is selective for bioethanol refinery and multi-functional biochar assembly using brittle stalk of corn mutant

As lignocellulose recalcitrance principally restricts for a cost-effective conversion into biofuels and bioproducts, this study re-selected the brittle stalk of corn mutant by MuDR-transposon insertion, and detected much reduced cellulose polymerization and crystallinity. Using recyclable CaO chemical for biomass pretreatment, we determined a consistently enhanced enzymatic saccharification of pretreated corn brittle stalk for higher-yield bioethanol conversion. Furthermore, the enzyme-undigestible lignocellulose was treated with two-step thermal-chemical processes via FeCl2 catalysis and KOH activation to generate the biochar with significantly raised adsorption capacities with two industry dyes (methylene blue and Congo red). However, the desirable biochar was attained from one-step KOH treatment with the entire brittle stalk, which was characterized as the highly-porous nanocarbon that is of the largest specific surface area at 1697.34 m2/g and 2-fold higher dyes adsorption. Notably, this nanocarbon enabled to eliminate the most toxic compounds released from CaO pretreatment and enzymatic hydrolysis, and also showed much improved electrochemical performance with specific capacitance at 205 F/g. Hence, this work has raised a mechanism model to interpret how the recalcitrance-reduced lignocellulose is convertible for high-yield bioethanol and multiple-function biochar with high performance.

Adsorption of phenol using adsorbent derived from Saccharum officinarum biomass: optimization, isotherms, kinetics, and thermodynamic study

The present research shows the application of Taguchi's design of experiment approach to optimize the process parameters for the removal of phenol onto surface of Saccharum officinarum biomass activated carbon (SBAC) from an aqueous solution to maximize adsorption capacity of SBAC. The effect of adsorption parameters viz. adsorbent dose (m), temperature (T), initial concentration (C0) and mixing time (t) on response characteristics i.e., adsorption capacity (qt) has been studied at three levels by using L9 orthogonal array (OA) which further analyzed by variance analysis (ANOVA) for adsorption data and signal/noise (S/N) ratio data by using 'larger the better' characteristics. Using ANOVA, the optimum parameters are found to be m = 2 g/L, C0 = 150 mg/L, T = 313 K and t = 90 min, resulting in a maximum adsorption capacity of 64.59 mg/g. Adopting ANOVA, the percentage contribution of each process parameter in descending order of sequence is adsorbent dose 59.97% > initial phenol concentration 31.70% > contact time 4.28% > temperature 4.04%. The phenol adsorption onto SBAC was best fitted with the pseudo-second-order kinetic model and follows the Radke-Prausnitz isotherm model. Thermodynamic parameters suggested a spontaneous, exothermic nature and the adsorption process approaches physisorption followed by chemisorption. Hence the application of Taguchi orthogonal array design is a cost-effective and time-efficient approach for carrying out experiments and optimizing procedures for adsorption of phenol and improve the adsorption capacity of SBAC.

Study of the Enhancements of Porous Structures of Activated Carbons Produced from Durian Husk Wastes

The idea of generating high-value practical materials, such as activated carbons, from agricultural wastes as a raw material has been a quite important trend recently due to its positive contributions to the environment and resource savings from biomass. In this paper, activated carbons prepared from durian husk waste by the KOH chemical activation method are studied. We focus on the effects of stages of the activating temperature on their properties. The optimum conditions for activation were a KOH/char ratio of 1:2 at the first and second activation process at the temperatures of 400 and 800 °C, respectively. The characterization results of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area showed that the obtained activated carbons have a high surface area and small pore size. The adsorption/desorption isotherms of the obtained activated carbons showed type I and type II isotherms. The chemical structure of obtained activated carbons did not show any variation in the surface functional groups. A feasible method to produce the activated carbons with a high surface area and high adsorption capability from durian husk waste was eventually demonstrated.

How to Obtain Maximum Environmental Applicability from Natural Silicates

Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as adsorbents for the organic pollutants in water tables using Methylene Blue (MB) as the model adsorbate. Among the selected materials, bentonite adsorbed as much as 237 mg/g, confirming its excellent suitability for pollutant removal. Spectral evidence confirmed successful MB immobilization at the bentonite surface. Furthermore, the thermal treatment of MB-saturated adsorbent in an inert atmosphere at 700 °C produced a carbon/silicate composite. EDX confirmed the formation of the nitrogen-doped carbon overlay on the silica scaffold and the obtained composite material was probed as an electrode material for oxygen reduction in an alkaline solution. Reduction proceeded via a two-electron mechanism with the main product being HO2−, a known nucleophile, which was subsequently used to degrade/demethylate MB. The composite showed a considerable 70% MB removal rate after an hour of electrochemical treatment. The synergy between the processes of adsorption of MB and the surface-generated HO2− dictates the efficiency of the method and points to a possible route for spent adsorbent reuse in the form of a durable product for environmental protection.

Removal of Cationic Organic Dye from Aqueous Solution by Chemical and Pyrolysis Activated Ulva lactuca

Ulva lactuca has been used to remove many toxic substances from industrial wastewater. In the present study we tried to optimize the efficiency of U. lactuca as an adsorbent of methylene blue (MB) in aqueous solution. U. lactuca was chemically treated with sulfuric acid (UL-H) and sodium hydroxide (UL-OH) and by a slow pyrolysis process (carbonization process) at high temperature T = 600 °C (UL-T) and compared to the nonactive Ulva (UL-NA) and the water insoluble substance (UL-WIS). Several spectroscopic analyses were carried out to detect the biosorption mechanisms of Ulva to remove MB in solution. The effects of different parameters on the adsorption process were studied, i.e., pH (2–10), mass concentration (1–10 g L−1), and contact time (0–120 min). The results showed that the best adsorption of MB by Ulva was at pH = 8, with 5 g L−1 of biomass at 75 min; the best adsorption capacity was 625.0 mg g−1 for UL-OH, which was able to remove more than 89% of MB compared to UL-T, whose removal rate did not exceed 5%. Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) indicated the presence of oxygenated functional groups with a highly porous surface. The kinetic studies confirmed that the majority of treatments follow the pseudo-second-order type. The mathematical models showed that Langmuir model is favorable to UL-OH, UL-WIS, and UL-NA. According to the experimental results, the primary treatment for U. lactuca is a promising environmentally friendly method and an economical strategy for removing MB from aqueous solution. This method can help address the growing demand for adsorbents used in environmental protection processes and the resultant increase in their price.