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Activated carbons were prepared from three parts of Dipterocarpus alatus fruit (wing, endocarp and pericarp), an abundant and renewable waste in Southeast Asia, by chemical activation using ZnCl2, FeCl3, H3PO4 and KOH and physical activation using CO2 and steam. This study indicated that activated carbon prepared from Dipterocarpus alatus fruit could be employed as a promising adsorbent for the removal of methylene blue from aqueous solution. ZnCl2 activation led to an activated carbon with a surface area of 843 m2 g−1 and was able to remove methylene blue from aqueous solution. Adsorption studies were performed and analysed using Langmuir and Freundlich isotherm equations. Adsorption data demonstrated an excellent fit with the Langmuir isotherm model, with the maximum adsorption capacity of 269.3 mg g−1 at equilibrium. Pseudo-first order and pseudo-second order kinetic models were used in this study to describe the adsorption mechanism. The results show that methylene blue adsorption is pseudo-second order, indicating that liquid film diffusion, intra-particle diffusion and surface adsorption coexisted during methylene blue adsorption on the activated carbon. The activated carbon prepared from Dipterocarpus alatus fruit is a low cost and effective adsorbent with a fast rate for the removal of methylene blue from aqueous solutions when compared with a number of activated carbons studied in the literature.

Biochar is a low-cost adsorbent with considerable potential for utilization as a water filtration medium; however, organic matter leaching from biochar can lead to the formation of disinfection by-products (DBPs). This study investigated the leaching of dissolved organic carbon (DOC) from eucalyptus-derived biochar and the formation of DBPs generated by chlorination and chloramination. Column experiments with empty bed contact times (EBCTs) of 10 and 30 min were conducted for 200 bed volumes (BVs). The highest DOC concentration (3.5 µg-C/g-biochar) was detected with an EBCT of 30 min. Chloroform (49 µg/L) and dichloroacetonitrile (7 µg/L) because of chlorination were found during the first five BVs, but were reduced thereafter. During the first 10 BVs, unknown chlorinated DBPs generated (CHOCl) by chlorination and chloramination (193 and 152 formulae, respectively) were tentatively identified via an unknown screening analysis. The release of DBP precursors from biochar tentatively identified in this study will impact water filtration applications.

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.

This present work aims to reduce the color of biodiesel from crude palm oil through the application of activated carbon prepared from chili stem waste. Chilli stem was converted into activated carbon using 30 wt% KOH at a ratio of 1:2 for 1 h, followed by carbonization at 500 oC under an N2 atmosphere for a further hour. Physico-chemical characteristics of the raw material and activated carbon were analyzed including thermogravimetric analysis, proximate analysis, and porosities. The results demonstrated that the activated carbon was a porous material with a highly mesoporous structure (84.5%). The surface area of activated carbon was 10.6 m2/g and it exhibited an average pore diameter of 27.25 nm which was suitable for the removal of large highly colored molecules. Batch adsorption experiments were performed to investigate the reduction in color of the biodiesel. Ratios of activated carbon to biodiesel of 0.002 and 0.1 w/v were used in the study. For comparison, the adsorption was also tested against a commercial activated carbon with a surface area of 1,130 m2/g, but lower average pore size of 3.72 nm. The chili stem activated carbon can reduce color by approximately 15% within 24 h and the maximum color reduction was 95% after 96 h for both activated carbon to biodiesel ratios. The color of biodiesel changes from dark red to yellow and eventually resulted in a pale yellow color with longer adsorption times and was deemed more attractive for use. Moreover, commercial activated carbon with its small pore size could not reduce the color, with a maximum reduction of only 3%.

Catalytic pyrolysis of waste plastics using low cost binder-free pelletized bentonite clay has been investigated to yield pyrolysis oils as drop-in replacements for commercial liquid fuels such as diesel and gasohol 91. Pyrolysis of four waste plastics, polystyrene, polypropylene, low density polyethylene and high density polyethylene, was achieved at a bench scale (1 kg per batch) to produce useful fuel products. Importantly, the addition of binder-free bentonite clay pellets successfully yielded liquid based fuels with increased calorific values and lower viscosity for all plastic wastes. This larger scale pyrolysis study demonstrated that use of a catalyst in powder form can lead to significant pressure drops in the catalyst column, thus slowing the process (more than 1 hour). Importantly, the use of catalyst pellets eliminated the pressure drop and reduced pyrolysis processing time to only 10 minutes for 1 kg of plastic waste. The pyrolysis oil composition from polystyrene consists of 95% aromatic hydrocarbons, while in contrast, those from polypropylene, low density polyethylene and high density polyethylene, were dominated by aliphatic hydrocarbons, as confirmed by GC-MS. FTIR analysis demonstrated that low density polyethylene and high density polyethylene oils had functional groups that were consistent with those of commercial diesel (96% similarity match). In contrast, pyrolysis-oils from polystyrene demonstrated chemical and physical properties similar to those of gasohol 91. In both cases no wax formation was observed when using the bentonite clay pellets as a catalyst in the pyrolysis process, which was attributed to the high acidity of the bentonite catalyst (low SiO2 : Al2O3 ratio), thus making it more active in cracking waxes compared to the less acidic heterogeneous catalysts reported in the literature. Pyrolysis-oil from the catalytic treatment of polystyrene resulted in greater engine power, comparable engine temperature, and lower carbon monoxide (CO) and carbon dioxide (CO2) emissions, as compared to those of uncatalysed oils and commercial fuel in a gasoline engine. Pyrolysis-oils from all other polymers demonstrated comparable performance to diesel in engine power tests. The application of inexpensive and widely available bentonite clay in pyrolysis could significantly aid in repurposing plastic wastes.

Highly porous carbons have been produced through an activated pyrolysis process from waste rice straw. The methodology avoids the use of extensive pre-treatments and utilises lower temperatures than those previously reported (700 °C), to generate materials suitable for water purification. Activation of rice straw was achieved with carbon dioxide, potassium hydroxide and phosphoric acid to yield porous carbonaceous materials and those prepared with phosphoric acid exhibited an extremely high proportion of mesoporosity (94–95%). The characterisation of the activated carbon demonstrated that rice straw pre-carbonisation at 400 °C prior to activation using potassium hydroxide at 700 °C, resulted in a material with surface area of 1973 m2/g. The pre-carbonised potassium hydroxide activated carbon was demonstrated to be highly effective at the adsorption of methylene blue (cationic dye) and congo red (anionic dye) with the adsorption capacity of 527.6 and 531.4 mg/g respectively. In many cases these adsorption capacities exceeded those of other absorbents previously reported within the literature but importantly require less pre-treatment. An economic assessment of the process demonstrated that these highly porous carbons from waste rice straw are cost competitive with other commercially available activated carbons. These activated carbons may find use as an inexpensive yet effective adsorbents for dye removal and also the mesoporous carbons can be utilised in other applications including catalysis and chromatography.

Triclocarban (TCC), an emerging endocrine disruptor, has been commonly found in municipal treated wastewater. Pseudomonas fluorescens MC46 (MC46), an effective TCC-degrading bacterium, could be applied to remove TCC from wastewater. In addition, application of a cell immobilization technique could possibly enhance its removal performance. This study examined microbial cells immobilized on waste biochar (from wood vinegar production) as a highly effective advanced wastewater treatment unit for TCC removal. TCC removal was investigated from real wastewater samples using the following treatments: biochar only, cell-immobilized biochar, and free cell systems in batch (short-term) and semi-batch (long-term) modes. The TCC adsorption capacities of original and potassium hydroxide-modified biochars (no cells) were 8.43 and 9.17 mg/g, respectively. During the batch experiment, the cell-immobilized modified biochar exhibited the highest TCC removal, 79.80%, in the model TCC solution. Five-cycle semi-batch experiments were utilized to investigate the reusability and performance of the treatment systems. After five cycles, the cell-immobilized modified biochar still achieved stable TCC removal (52%) due to the integration of adsorption and biodegradation. Free MC46 cells and biochars (no MC46 cells) only removed 32% and 2% of TCC, respectively, due to cell washout/death and sorbent exhaustion. This important work clearly demonstrates the significant potential for the future utilization of cell-immobilized biochars in a sustainable wastewater treatment system. Furthermore, the use of renewable agro-industrial wastes aid in the development of a strong circular bio-based economy.

Highly mesoporous carbon-zinc oxide nanocomposites were synthesized from rice straw through a simple pyrolysis method. These carbon-zinc oxide nanocomposites were ideal for adsorption and degradation of toxic dyes from wastewater. Synthetic methodology utilized a 1-step zinc chloride activation process that eliminated the need for acid washing, yielding a graphitic material with specific surface area of 942.7 m2 g−1 and 99% mesoporosity. X-ray diffraction and X-ray photoelectron spectroscopy patterns indicated the existence of zinc oxide and turbostratic graphite. Transmission electron microscopy images revealed zinc oxide particles sizes ranging between 20 and 100 nm. Surprisingly, graphene-like-sheets were also observed within the nanocomposite structure. Adsorption capacities for methylene blue and congo red were 399 mg g−1 and 410 mg g−1 respectively. By retaining zinc oxide in the carbon structure, catalytic degradation of dyes was possible in the presence of ultraviolet radiation. The synergistic effect of adsorption and photocatalytic degradation increased the maximum dye removal of methylene blue to 614 mg g−1, while congo red removal was exceptionally high at 2628 mg g−1.

Highly porous carbon-silica composites (CSC) were prepared for the first time through a simple wet impregnation process and subsequent pyrolysis of low-value sugarcane by-products, namely molasses. These CSC materials demonstrate a distinct range of functionalities, which significantly differ from similar materials published in the literature. Importantly, the carbon-silica composites prepared at 800°C exhibited exceptional adsorption capacities for the azo-dye congo red (445 mg g −1 ), due to the graphitic carbon coating and unique functionality including C-O-C within the porous structure. Congo red adsorption capacity of the highly mesoporous graphitic carbon-silica composites significantly exceeds that of commercial activated carbon and silica, these carbon-silica composites therefore represent an effective step towards the development of porous bio-derived adsorbent for remediation of dye wastewaters. Both the porous properties (surface area and pore size distribution) and the functionality of the carbon coating were dependent on the temperature of preparation. The sustainable synthetic methods employed led to a versatile material that inherited the mesoporosity characteristics from the parent silica, demonstrating mesoporous volumes greater than 90% (as calculated from the total pore volume). Adsorption on the 800°C prepared carbon-silica composites demonstrated an excellent fit with the Langmuir isotherm and the pseudo-first-order kinetic model.

Dipterocarpus alatus tree grows prolifically throughout Thailand and can be tapped to yield significant quantities of oil to be used as natural diesel. However, such practices lead to waste dried fruit dropping from the tree. At present, there is no utilization of this dropped fruit, therefore costeffective processes need to be applied to obtain higher value products from this waste. A possible to utilization is the conversion to activated carbon for adsorption applications including the removal of heavy metals, dyes, and other contaminants in water purification and other decontamination process. A major challenge of current commercial activated carbon is the high production cost and recently it has been shown that chemical activators comprise a significant proportion of these costs. This feasibility study investigates the use of Dipterocarpus alatus fruit as raw material to produce low cost activated carbon adsorbents. Activated carbon was prepared from Dipterocarpus alatus fruit: endocarp, mesocarp, and wing by chemical activation with ZnCl2, FeCl3, and KOH. Each part of the fruit was impregnated with 30 wt% activating agent at a ratio of 1:2 for 1 h and then carbonized at 500 oC for a further 1 h. The surface area, pore volume, and average pore size of the resulting carbons were characterized by nitrogen gas adsorption. Activation of mesocarp with ZnCl2, KOH, and FeCl3 gave activated carbons with the surface area of 447, 256, and 199 m2/g, respectively. In the same way, ZnCl2 activation gave a maximum surface area of 312 and 278 m2/g for wing and endocarp, respectively. All of the aforementioned samples have an average pore size of around 2 nm. In contrast, KOH and FeCl3 activation of wing and endocarp produced activated carbon with very low surface area (below 25 m2/g), but with an average pore size of 5- 14 nm. The maximum surface area of activated carbon prepared from Dipterocarpus alatus fruit was higher than some literature examples for activated carbon from other biomass. Consequently, Dipterocarpus alatus fruit demonstrated significant potential as a feedstock for the preparation of low cost activated carbons.

Consumption of water containing high proportions of manganese could cause Parkinson's like symptoms and damage the central nervous systems. This study aims to investigate the potential of manganese removal through the development of microbial cell-immobilized biochar. The wood vinegar industry generates a large volume of carbonized wood waste (natural biochar) from the pyrolytic process. This is the first investigation utilizing this low value waste combined with biological treatment for water purification. Raw and hydrogen peroxide-modified biochars were used to immobilize an effective manganese-oxidizing bacterium, Streptomyces violarus strain SBP1 (SBP1). The results demonstrated that the modified biochar had a higher proportion of oxygen-containing functional groups leading to better manganese removal. Manganese adsorption by the modified biochar fitted pseudo-second-order and Langmuir models with the maximum adsorption capacity of 1.15 mg g−1. The modified biochar with SBP1 provided the highest removal efficiency at 78%. The advanced synchrotron analyses demonstrated that manganese removal by the biochar with SBP1 is due to the synergistic combination of manganese adsorption by biochars and biological oxidation by SBP1.

A Grand Canonical Monte Carlo simulation method is used to study the adsorption of water in activated carbon and carbon nanotubes, and the simulation results are compared with the experimental data obtained gravimetrically. To investigate the role of functional groups on water adsorption, the hydroxyl group is chosen and grafted at various locations on the surface. The spacing between adjacent nanotubes is varied. For small spacings, it has no effect on the isotherms if the functional group is located outside the central tube. This is due to the geometrical constraint that hinders the hydrogen bonding for water molecules to form clusters. However, the onset of adsorption occurs at lower pressures for both inside and outside the tubes when the functional group is positioned near the interstice. For larger separation, clusters are readily formed and the functional group enhances adsorption isotherms both inside and outside the tubes, and capillary condensation occurs in the interstices. For slits, the position and concentration of functional group affect adsorption. At low temperatures, water isotherms have an unusual behavior in that the 10°C isotherm is less than that at 15°C, which is in opposite to what thermodynamics suggests. However this behavior can be explained with our computer simulation, suggesting that water adsorption in carbon could be affected strongly by the metastable state and the slow kinetics of cluster formation at low temperatures.

The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its sur- face chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method. Under all treatment conditions of increasing time, temperature and oxidant concentration, liquid oxidation with HNO3, H2O2 and (NH4)2S2O8 and air oxidation led to the increase of acidic group concentration, with carboxylic acid showing the largest percentage increase and air oxidation at the maximum allowable temperature of 350 o C pro- duced the maximum content of both carboxylic acid and total acidic group. Nitric acid oxidation of chemically activated carbon produced higher total acidic content but a lower amount of carboxylic acid compared to the oxidized carbon from physical activation. The increased contents of acidic groups on oxidized carbons greatly enhanced the adsorption capacity of water vapor and heavy metal ions.

This work presents the behavior of water adsorption in the activated carbons with different porous structure derived by varying the level of char burn-off. Water adsorption isotherms of activated carbons prepared from longan seed at three different burn-offs (19, 26 and 60%) were measured gravimetrically. These obtained carbons were dif- ferent in terms of their pore size distribution and also the surface functional group properties by showing an increasing of total pore volume and the concentration of surface functional groups with increasing in the burn-off level. The water adsorption isotherms showed that the behavior and amount of water uptake could be divided into three consecutive ranges of relative pressure, 0.0-0.3, 0.3-0.7 and 0.7-0.94, corresponding to adsorption in ultramicropores, supermi- cropores, and mesopores, respectively. The isotherm data were simulated by a cluster model proposed by Do and Do. The correlation was found to be satisfactory over the entire range of relative pressure only with the lowest burn-off carbon which contained mainly micropores. For higher burn-off carbons, which showed increasing proportions of mes- opores, the model needed to be modified by increasing the cluster size of the adsorbed water molecules from 5 to 20 for adsorption at relative pressures greater than about 0.7.

This work focused on the preparation of activated carbon from eucalyptus and wattle wood by physical activation with CO2. The preparation process consisted of carbonization of the wood samples under the flow of N2 at 400°C and 60 min followed by activating the derived chars with CO2. The activation temperature was varied from 600 to 900°C and activation time from 60 to 300 min, giving char burn-off in the range of 20/2-83%. The effect of CO2 concentration during activation was also studied. The porous properties of the resultant activated carbons were characterized based on the analysis of N2 adsorption isotherms at −196°C. Experimental results showed that surface area, micropore volume and total pore volume of the activated carbon increased with the increase in activation time and temperature with temperature exerting the larger effect. The activated carbons produced from eucalyptus and wattle wood had the BET surface area ranging from 460 to 1,490 m2/g and 430 to 1,030 m2/g, respectively. The optimum activation conditions that gave the maximum in surface area and total pore volume occurred at 900°C and 60 min for eucalyptus and 800°C and 300 min for wattle wood. Under the conditions tested, the obtained activated carbons were dominated with micropore structure (∼80% of total pore volume).