The Effect of Impregnation Ratio on the Surface Characteristics of Gigantochloa Verticillata Bamboo-Activated Carbon

The activation process is the final stage in the manufacturing of activated carbon that can be carried out physically or chemically. This paper focuses on characterizing the surface properties of activated carbons from Gigantochloa verticillata bamboo that are chemically activated at 750°C under different impregnation ratios (IRs) of 1:1, 2:1, and 3:1. The activated carbons produced were denoted as IR1-AC, IR2-AC, and IR3-AC for impregnation ratios of 1:1, 2:1, and 3:1, respectively. Characterizations include TGA, SEM, and adsorption isotherm tests. The results of the research show that variation of the impregnation ratio yielded fluctuated content of proximate elements and surface properties of activated carbons. The highest fixed carbon of 75.69% and the lowest ash of 13.10% were obtained by IR2-AC. The highest surface area of 511.10 m2/g and pore volume of 0.561 cc/g was obtained by IR3-AC and IR2-AC, respectively. The activated carbon pores are distributed in micropores and mesopores areas with average pore diameters of 1.245, 2.494, and 1.984 nm for IR1-AC, IR2-AC, and IR3-AC, respectively. The existence of the pores can be found on the surface morphology of activated carbons.

Preparation of Activated Carbon From Sunflower Straw by H3PO4 Activation and Its Application for Acid Fuchsin Adsorption

In this work, sunflower straw (SS) was used as the raw material, H3PO4 was used as the activator, and the sunflower straw activated carbon (SSAC) was prepared by the one-step activation method under the impregnation ratio of 1:1, 1:2, 1:3, 1:5 (SS/H3PO4, g/g). The adsorption of acid fuchsin (AF) simulated dye wastewater by SSAC prepared under different immersion ratios has been studied. As the impregnation ratio increases, the pore structures of SSAC changed greatly. SSAC3 had the largest specific surface area (1794.01 m2/g), and SSAC4 had the smallest microporosity (0.0527 cm3/g) and the largest pore volume (2.549 cm3/g). The adsorption kinetics of four types of SSAC to AF were more in line with the quasi-second-order adsorption kinetic model. The Langmuir isotherm model was suitable for describing SSAC3 and SSAC4, and the Freundlich isotherm model was suitable for describing SSAC1 and SSAC2. Thermodynamics showed that the adsorption process was spontaneous and endothermic. At 303 K, SSAC4 showed a removal rate of 97.73% for 200 mg/L AF, and the maximum adsorption capacity of 2763.36 mg/g, which was the highest among the four types of SSAC. This study shows that the sunflower straw activated carbon prepared by the H3PO4 one-step activation method is a green and efficient carbon material and has great application potential in the treatment of dye-containing wastewater.

A Review on Preparation and Characterization of Activated Bio-Char

Activated charcoal (AC) is a carbonaceous material with high surface area due to high degree of micro-porosity which makes it a very versatile adsorbent for utilization in industrial, medicinal, environmental and other fields. Ligno-cellulosic biomass (eg. pine needles, paddy stubbles, other waste agricultural residue) can be a prominent raw material for activated bio-char due to its abundance, slow decomposition (which lead to fire/ air pollution). The main factors which affect the AC characteristics (surface area, micropore volume, mesopore volume) are biomass properties, impregnation ratio, impregnation time, activation temperature and activation time. The specific surface area, micropore, mesopore decreases after optimum value with continually increase in impregnation ratio and impregnation time. The activation temperature and impregnation ratio also affect the AC yield significantly. Sorption capacity get affected by adsorbent doses, contact time, agitation speed, adsorption temperature due to availability of active binding sites, adsorptive forces/ bonds.

Straw-Based Activated Carbon: Optimization of the Preparation Procedure and Performance of Volatile Organic Compounds Adsorption

Straw is one of the largest agricultural biowastes and a potential alternative precursor of activated carbon. Activated carbon prepared from different types of straw have great differences in structure and adsorption performance. In order to explore the performance of different straw-based activated carbon in volatile organic compounds adsorption, five common straws were selected as potential source materials for the preparation of SAC. The straw-based activated carbons were prepared and characterized via a thermo-gravimetric analysis, scanning electron microscope and the Brunauer–Emmett–Teller method. Among the five straw-based activated carbons, millet straw-derived activated carbon exhibited superior properties in SBET, Smic and adsorption capacities of both toluene and ethyl acetate. Furthermore, the preparation process of millet straw activated carbon was optimized via response surface methodology, using carbonization temperature, carbonization time and impregnation ratio as variables and toluene adsorption capacity, ethyl acetate adsorption capacity and activated carbon yield as responses. The optimal preparation conditions include a carbonization temperature of 572 °C, carbonization time of 1.56 h and impregnation ratio (ZnCl2/PM, w/w) of 1.60, which was verified experimentally, resulting in millet straw activated carbon with a toluene adsorption capacity of 321.9 mg/g and ethyl acetate adsorption capacity of 240.4 mg/g. Meanwhile, the adsorption isothermals and regeneration performance of millet straw activated carbon prepared under the optimized conditions were evaluated. The descriptive ability of the isothermals via the Redlich–Peterson equation suggests a heterogeneous surface on millet straw activated carbon. Recyclability testing has shown that millet straw activated carbon maintained a stable adsorption capacity throughout the second to fifth cycles. The results of this work indicate that millet straw activated carbon may be a potential volatile organic compound adsorbent for industrial application.

Fine Activated Carbon from Rubber Fruit Shell Prepared by Using ZnCl2 and KOH Activation

Fine activated carbon (FAC) is prepared from rubber fruit shells (RFS) using two chemical activating agents (ZnCl2 and KOH) and three impregnation ratios (1:3, 1:4, and 1:5). The Brunauer–Emmett–Teller (BET) results show that for a constant impregnation ratio, the ZnCl2 activating agent yields a higher specific surface area than the KOH agent. In particular, for the maximum impregnation ratio of 1:5, the FAC prepared using ZnCl2 has a BET surface area of 456 m2/g, a nitrogen absorption capacity of 150.38 cm3/g, and an average pore size of 3.44 nm. Moreover, the FAC structure consists of 70.1% mesopores and has a carbon content of 80.05 at.%. Overall, the results confirm that RFS, activated using an appropriate quantity of ZnCl2, provides a cheap, abundant, and highly promising precursor material for the preparation of activated carbon with high carbon content and good adsorption properties

Modeling and Optimization of Biochar Based Adsorbent Derived from Kenaf Using Response Surface Methodology on Adsorption of Cd2+

Cadmium is one of the most hazardous metals in the environment, even when present at very low concentrations. This study reports the systematic development of Kenaf fiber biochar as an adsorbent for the removal of cadmium (Cd) (II) ions from water. The adsorbent development was aided by an optimization tool. Activated biochar was prepared using the physicochemical activation method, consisting of pre-impregnation with NaOH and nitrogen (N2) pyrolysis. The influence of the preparation parameters—namely, chemical impregnation (NaOH: KF), pyrolysis temperature, and pyrolysis time on biochar yield, removal rate, and the adsorption capacity of Cd (II) ions—was investigated. From the experimental data, some quadratic correlation models were developed according to the central composite design. All models demonstrated a good fit with the experimental data. The experimental results revealed that the pyrolysis temperature and heating time were the main factors that affected the yield of biochar and had a positive effect on the Cd (II) ions’ removal rate and adsorption capacity. The impregnation ratio also showed a positive effect on the specific surface area of the biochar, removal rate, and adsorption capacity of cadmium, with a negligible effect on the biochar yield. The optimal biochar-based adsorbent was obtained under the following conditions: 550 °C of pyrolysis temperature, 180 min of heating time, and a 1:1 NaOH impregnation ratio. The optimum adsorbent showed 28.60% biochar yield, 69.82% Cd (II) ions removal, 23.48 mg/g of adsorption capacity, and 160.44 m2/g of biochar-specific area.

Removal of Acid Red 88 Using Activated Carbon Produced from Pomelo Peels by KOH Activation: Orthogonal Experiment, Isotherm, and Kinetic Studies

Activated carbon (PPAC) from pomelo peels was prepared by carbonization and KOH activation. The performance of PPAC was assessed by removing acid red 88 (AR88) in aqueous solution. The most suitable activation processes were found by orthogonal experiments, aimed to achieve the maximum of removal capacity of AR88. Moreover, the possible mechanisms of adsorption were studied through the results of characterization, isotherm fitting, and kinetics simulation. Results showed the preparation parameter that mattered the most to AR88 removal efficiency was the activation temperature of PPAC, followed by impregnation ratio and activation time. The optimal preparation conditions of PPAC were at activation temperature 800°C, activation time 90 min, and impregnation ratio 2.5 : 1. The characterization results showed optimal PPAC had a microporous and amorphous carbon structure whose BET specific area and total pore volume were 2504 m2/g and 1.185 cm3/g, respectively. The isotherm fitting demonstrated that the sorption process followed the Langmuir model, and theoretical maximal sorption value was 1486 mg/g. The kinetics simulation showed that the pseudo-second-order model described the sorption behavior better, suggesting chemisorption seemed to be the rate-limiting step in the adsorption process. This work presented that PPAC was a promising and efficient adsorbent for AR88 from water.

Preparation of Activated Carbons based Balanites Aegyptiaca Shells by Chemical Activation: Optimization Conditions Using the Methodology of Experimental Design

The optimization conditions of preparation of activated carbons based Balanites aegytiaca shells by chemical activation was investigated. The effects of three parameters of preparation namely, the activation temperature (600-800 °C), impregnation ratio (1:4-3:8) and residence time (60-120 min) were thoroughly studied on the activated carbon yield (Yld, Y1), iodine number (ION,Y2) and methylene blue number (MBN, Y3) using the Methodology of Experimental Design (MED). The analysis of variance (ANOVA) under the experimental domain revealed that, the activation temperature of 800 °C, residence time of 02hrs and impregnation ratio of 1:2 were the optimum conditions of preparation leading to activated carbon yield of 23.0%, iodine number of 889.0 mg/g and methylene blue number of 9.7 mg/g. The polynomial equation showed that the three parameters were both synergetic and antagonistic on the responses retained. The higher values of iodine numbers obtained alongside the experimental matrix is an indication that the activated carbons so prepared were mainly microporous.