Activated Carbon Adsorption Research Articles

Surface Modification of Tea-Waste-Based Biochar Adsorbent: Synthesis, Characterization, and Batch Adsorption for the Removal of Zidovudine ARV Drug and Phenol

Domestic, agricultural, and industrial waste has been investigated as a substitute for activated carbon adsorbents. For instance, the transformation of tea waste to biochar can be utilized as a substitute for activated carbon adsorbents. In this study, tea waste-based biochar adsorbents (biochar, biochar/reduced graphene oxide (biochar/rGO), biochar/reduced graphene oxide/deep eutectic solvent-cetyltrimethylammonium bromide (biochar/rGO/DES-CTAB), and biochar/reduced graphene oxide/deep eutectic solvent-glycerol (biochar/rGO/DES-glycerol)) were synthesized by simple thermal treatment of tea waste and sucrose followed by modification with reduced graphene oxide and deep eutectic solvents. The obtained materials were characterized using a range of spectroscopy techniques, Fourier Transformed Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy–Energy-Dispersive X-ray Spectroscopy (SEM–EDS), Brunauer, Emmett, and Teller (BET) surface area analysis, and pH at point of zero charge (pH PZC). The obtained results showed that the principal material, i.e., biochar was modified, and FTIR results confirmed the presence of added functional groups. SEM images revealed surface structural changes, and BET showed a decrease in pore size from 10.16 nm to 6.87 nm. The synthesized materials were applied for the removal of ZDV and phenol from the aqueous medium. Batch adsorption studies were conducted to optimize operating parameters such as the adsorbent dose, solution pH, contact time, and initial concentration. Pseudo-first-order (PFO), Pseudo-second-order (PSO), and intraparticle diffusion (IPD) kinetic models were determined to investigate the mechanism of the adsorption process. The coefficient of correlation, R2, was used to determine the best fit of the kinetic models. The adsorption results showed that the DES-glycerol-modified adsorbent was more efficient in removing the pollutants ZDV and phenol than biochar, biochar/rGO, and biochar/rGO/DES-CTAB adsorbents. In addition, the results showed that an acidic medium of pH 2.00 and a contact time of 1 h 30 min and 30 min is sufficient for removing ZDV and phenol, respectively, from an aqueous medium.

Thermal treatment of H3PO4-impregnated hydrochar under controlled oxygen flows for producing materials with tunable properties and enhanced diclofenac adsorption

The chemical activation of biomass with phosphoric acid under an oxygenated atmosphere has been extensively studied in various papers. However, there is still uncertainty about how the oxygenated atmosphere affects the evolution of activated carbon properties, as the concentration of oxygen in the activation atmosphere has not been explored as an activation variable. Hence, this paper aims to fill the gap by exploring the effect of oxygen concentration on the activation process. The H3PO4-impregnated hydrochar was heated at 500 °C, under atmospheres containing various concentrations of oxygen. The evolution of activated carbons' properties was assessed by various techniques, including FTIR, SEM-EDS, N2-physisorption, CHNS/O elemental analysis, pHpzc, and Boehm titration. Additionally, the impact of oxygen concentration on the adsorption capacity was examined using diclofenac as a model pollutant. It was found that the activated carbons’ microporosity and surface functionality can be improved and controlled by changing the oxygen concentration in the activation atmosphere. This led to enhanced π-π and hydrogen bonding interactions between diclofenac molecules and activated carbons, resulting in increased adsorption capacities. This study emphasizes the importance of oxygen concentration as an activation variable, providing valuable insights for designing effective activated carbon adsorbents.

Conversion of the hydrochar recovered after levulinic acid production into activated carbon adsorbents

Levulinic acid production by acid-catalyzed hydrothermal conversion of (ligno)cellulosic biomass generates significant amounts of carbonaceous hydrochar, which is currently considered a final waste. In this work, the hydrochar recovered after the levulinic acid production, was subjected to cascade pyrolysis and chemical activation treatments (by H3PO4 or KOH), to synthesize activated carbons. The pyrolysis post-treatment was already effective in improving the surface properties of the raw hydrochar (Specific Surface Area: 388 m2/g, VP: 0.22 cm3/g, VMESO: 0.07 cm3/g, VMICRO: 0.14 cm3/g), by removing volatile compounds. KOH activation resulted as the most appropriate for further improving the surface properties of the pyrolyzed hydrochar, showing the best surface properties (Specific Surface Area: 1421 m2/g, VP: 0.63 cm3/g, VMESO: 0.10 cm3/g, VMICRO: 0.52 cm3/g), which synergistically makes it a promising system towards adsorption of CO2 (∼90 mg/g) and methylene blue (∼248 mg/g). In addition, promising surface properties can be achieved after direct chemical activation of the raw hazelnut shells, preferably by H3PO4 (Specific Surface Area: 1918 m2/g, VP: 1.34 cm3/g, VMESO: 0.82 cm3/g, VMICRO: 0.50 cm3/g), but this choice is not the smartest, as it does not allow the valorization of the cellulose fraction to levulinic acid. Our approach paves the way for possible uses of these hydrochars originating from the levulinic acid chain for new environmental applications, thus smartly closing the biorefinery loop of the hazelnut shells.

Effect of air staging and porous inert material on the emission of volatile organic compounds in solid biomass combustion

The present paper delves into experimental data to assess the effects of the inclusion of a zirconium porous medium in the emissions of a laboratory-scale biomass combustor, with a focus on particulate matter and volatile organic compounds. While other studies have focused on the effects of the material on solid particulate matter or gaseous emissions, this research is focused on volatiles, their capture and storage. A novel sampling train for the capture of volatiles has been designed based on active carbon adsorption on a refrigerated environment, and its performance was evaluated through thermogravimetric analysis, showing the affinity of this porous medium towards lighter organic compounds. The retention time of the sample was also studied, and the data revealed that after three to six hours the sample had degraded significantly when stored in airtight plastic bags inside a glass desiccator at 22 °C. An analysis of the particulate matter emitted was also carried out. Volatile organic compounds were also found to follow the behavior of particulate matter, with the scenarios where low solid particles were emitted being also those in which volatiles release was minimized.

Simultaneous nitrogen and sulfur removal through synergy of sulfammox, anammox and sulfur-driven autotrophic denitrification in a modified bioreactor enhanced by activated carbon

Anaerobic ammonium (NH4+ - N) oxidation coupled with sulfate (SO42−) reduction (sulfammox) is a new pathway for the autotrophic removal of nitrogen and sulfur from wastewater. Sulfammox was achieved in a modified up-flow anaerobic bioreactor filled with granular activated carbon. After 70 days of operation, the NH4+ - N removal efficiency almost reached 70%, with activated carbon adsorption and biological reaction accounting for 26% and 74%, respectively. Ammonium hydrosulfide (NH4SH) was found in sulfammox by X-ray diffraction analysis for the first time, which confirmed that hydrogen sulfide (H2S) was one of the sulfammox products. Microbial results indicated that NH4+ - N oxidation and SO42− reduction in sulfammox were carried out by Crenothrix and Desulfobacterota, respectively, in which activated carbon may operate as electron shuttle. In the 15NH4+ labeled experiment, 30N2 were produced at a rate of 34.14 μmol/(g sludge·h) and no 30N2 was detected in the chemical control group, proving that sulfammox was present and could only be induced by microorganisms. The 15NO3− labeled group produced 30N2 at a rate of 88.77 μmol/(g sludge·h), demonstrating the presence of sulfur-driven autotrophic denitrification. In the adding 14NH4+ and 15NO3− group, it was confirmed that NH4+ - N was removed by the synergy of sulfammox, anammox and sulfur-driven autotrophic denitrification, where the main product of sulfammox was nitrite (NO2−) and anammox was the main cause of nitrogen loss. The findings showed that SO42− as a non-polluting species to environment may substitute NO2− to create a new “anammox” process.

Enhanced adsorption of 2,4-dichlorophenoxyacetic acid using low-temperature carbonized Peltophorum pterocarpum pods and its statistical physics modeling

The usage of various herbicides in the agricultural field leads to water pollution which is a big threat to the environment. Herein, the pods of the Peltophorum pterocarpum tree were used as a cheap resource to synthesize activated carbon (AC) by low-temperature carbonization to remove 2,4-dichlorophenoxyacetic acid (2,4-D) – an abundantly used herbicide. The exceptional surface area (1078.34 m2/g), mesoporous structure, and the various functional groups of the prepared AC adsorbed 2,4-D effectively. The maximum adsorption capacity was 255.12 mg/g, significantly higher than the existing AC adsorbents. The adsorption data satisfactorily modelled using Langmuir and pseudo-second-order models. Also, the adsorption mechanism was studied using a statistical physics model which substantiated the multi-molecular interaction of 2,4-D with the AC. The adsorption energy (<20 kJ/mol) and thermodynamic studies (ΔH°: −19.50 kJ/mol) revealed the physisorption and exothermicity. The practical application of the AC was successfully tested in various waterbodies by spiking experiments. Hence, this work confirms that the AC prepared from the pods of P. pterocarpum can be applied as a potential adsorbent to remove herbicides from polluted waterbodies.

Correction to: Effective transport properties for the pyridine-granular activated carbon adsorption system

Correction to: Effective transport properties for the pyridine-granular activated carbon adsorption system

Ozone membrane contactor for tertiary treatment of urban wastewater: Chemical, microbial and toxicological assessment

A membrane ozone contactor, operated under continuous mode, was applied to promote the tertiary treatment of urban wastewater (UWW), targeting the removal of contaminants of emerging concern (CECs), bacterial disinfection, and toxicity reduction. This system relies on the homogeneous radial distribution of ozone (O3) in the reaction zone by “titration” through a microfiltration borosilicate tubular membrane, while the UWW swirls around the membrane and drags the O3 microbubbles generated in the membrane shell-side. The membrane is coated with titanium dioxide (TiO2-P25) and radiation can be externally supplied via four UV lamps. The ozonation tests were carried out with secondary-treated UWW collected in different seasons (winter and summer) and spiked with a mix of 19 CECs (10 μg L−1 each). For an O3 dose of 18 g m−3, the best performance was obtained by increasing the O3 concentration (maximum [O3]G,inlet of 200 g Nm−3) and decreasing the gas flow rate (minimum QG of 0.15 Ndm3 min−1), providing the highest ozone transfer yield (88 %) and, thus higher specific ozone dose (g O3 per g dissolved organic carbon). Under these conditions, removals >80 % or concentrations below the limit of quantification were obtained for up to 13 of the 19 CECs and reductions up to 5 log units for total heterotrophs and below the limit of detection for enterobacteria and enterococci. Tests including a UVC dose of 0.10 kJ L−1 enhanced disinfection ability but had no impact on CECs oxidation. After ozonation, the abundance of antibiotic resistant bacteria was reduced but not eliminated, and microbial regrowth after 3-day storage was observed. No toxic effect was detected on zebrafish embryos using a dilution factor of 4 for the ozonized UWW and when granular activated carbon adsorption was subsequently applied the dilution factor decreased to 2.

Adsorption efficiency of activated carbon prepared from Palm kernel shells in removal of dyes used in textile industry

Palm shell has been utilized to create an effective activated carbon adsorbent in this investigation. The adsorbent is being used to remove direct dyes from dyeing waste in textiles. Thermo Gravimetric Analysis, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy and Atomic Absorption Spectroscopy were used to characterize the synthesized carbon. The particles are very porous and irregular in shape, based on the SEM analysis. This particle shape is effective at removing dye and toxic metals. TGA analysis has been shown to be highly stable under varied temperature circumstances. The FTIR data revealed the existence of functional groups that are responsible for dye and toxic metal elimination. The AAS analysis showed that dye degrading ability rises at a time interval and the adsorption ability of activated carbon. These findings suggest that Palm shell carbon could be used as a low cost alternative to commercial activated carbon in the removal of dyes from wastewater.

Algal organic matter impact on 2-methylisopropanol and geosmin adsorption by activated carbon: Variation with algae growth and decay, prediction by fluorescence surrogates

Algae-producing odorants have negative effects on the aesthetic quality of drinking water, and activated carbon adsorption is commonly used to abate the odorants. However, in eutrophic waters, algal organic matter (AOM) produced by the dominant cyanobacteria (e.g., Microcystis aeruginosa) strongly interferes with the activated carbon adsorption of trace odorants from source waters. In this study, the applicability of using spectrometric surrogates to evaluate the effect of AOM from Microcystis aeruginosa on odorant adsorption by activated carbon was investigated. During the stationary phase, the DOC concentration of extracellular organic matter (EOM) increased due to algal metabolism (from 3.52 mg/L to 7.81 mg/L) and further accumulated (to 12.40 mg/L) during the decline phase due to the release of intracellular organic matter (IOM), resulting in increased competition against odorants. The adsorption of chromogenic organics in AOM was first evaluated to screen possible spectrometric surrogates for predicting odorant adsorption. The fluorescence component (Ex: 260 nm/Em: 400–460 nm) was the best candidate for predicting odorant adsorption in both AOM solutions and reservoir water. In contrast, poor performance was found for the commonly used UV absorbance at 254 nm and protein-like fluorescence components, due to the weak adsorbability of corresponding chromogenic materials. Our results indicate that fluorescence spectroscopy is promising in predicting odorant adsorption with AOM interference in source waters.

Recyclable dynamic imine‐based nonionic surfactants and potential use in postprocessing of eluted emulsions

AbstractRecovery of surfactants and retrieval of hydrocarbons from eluted emulsions in surfactant‐enhanced washing are essential to save useful resources and avoid secondary contamination. A novel nonionic surfactant of C6‐DIB‐PEG has been constructed by using a dynamic imine bond (DIB) as the linker between hexyl amine (C6‐NH2) and an aromatic aldehyde modified polyethylene glycol (PEG‐CHO). The results presented in this study reveal that an oil‐in‐water emulsion of tetradecane‐H2O stabilized by C6‐DIB‐PEG is pH‐switched. Upon reaction with HCl, C6‐DIB‐PEG readily converts to its inactive forms C6‐NH3+Cl− and PEG‐CHO when the pH is changed from 12.0 to 4.0, resulting in a complete tetradecane‐water two‐phase separation. Both C6‐NH3+Cl− and PEG‐CHO are insoluble in tetradecane but soluble in water, allowing subsequent retrieval of nearly surfactant‐free tetradecane. Recovery of C6‐DIB‐PEG was enabled by treating aqueous solutions of C6‐NH3+Cl− and PEG‐CHO with NaOH after pH was increased from 4.0 to 12.0. The pH‐switched C6‐DIB‐PEG renders a potential use for oil retrieval and surfactant recovery in the postprocessing of eluted emulsions, as demonstrated by the C6‐DIB‐PEG‐enhanced washing of tetradecane‐contaminated sand. Around 95.2% of the tetradecane and about 99.7% of the C6‐DIB‐PEG were retrieved and recycled over 10 cycles of washing. In addition, the total organic carbon (TOC) of the residual wastewater was remarkably reduced from around 7065.3 to ~54.1 mg L−1 after NaHSO3 treatment followed by ion‐exchange resin and active carbon adsorption.

Evaluation of absorbent sheet to prevent anticancer drugs contamination spread in urine

Medically, anticancer drugs contamination leading to human exposure has become an issue. The urine of patients receiving chemotherapy contains anticancer drugs. If urine containing anticancer drugs is excreted, the anticancer drugs are scattered around the toilet bowl, then adhere to slipper soles and spread. Therefore, we developed an absorbent sheet containing activated carbon that absorbs anticancer drugs and prevents anticancer drug contamination spread. In this article, we report the data on the sheet performance evaluation. In artificial urine solutions, 100 μL (20 drops) of cyclophosphamide (CPA; 2,000 μg/mL), methotrexate (MTX; 6,000 μg/mL), and paclitaxel (PTX; 200 μg/mL) were dropped onto the stainless plate of two commercially available medical sheets (Pitapa SheetⓇ; control product 1 and Absocare sheetⓇ; control product 2) and a newly developed sheet (HD Safe Sheet-Neo, test product). Polyvinyl chloride (PVC) slippers were placed on the sheets for 30 s, and anticancer drugs that adhered to the slippers were quantified. We compared the drug quantities that were transferred to the slippers from different sheets. An average of 31.5%, 38.7%, and 50.5% of each of the dropped anticancer agents (CPA, MTX, and PTX, respectively) adhered to the slipper sole. Compared to that of the control product 2, the average adhesion of CPA and MTX was significantly reduced in the test product containing activated charcoal (224 vs 2 μg, p < .050 and 2,235 vs 19 μg, p < .050). Contrastingly, there was no significant difference in the PTX mean adherence (35 vs 13 μg). Activated carbon adsorbs anticancer drugs in urine. The test product containing activated charcoal reduced the amount of scattered anticancer drugs that adhered to the slippers. The results suggest that the activated carbon sheet may prevent anticancer drugs contamination spread in urine.

Pemanfaatan Sisa Kulit Kayu sebagai Karbon Aktif dalam Pengolahan Air Lindi Industri Pulp and Paper

The pulp and paper industry produces the remaining bark as solid waste, where this solid waste pile when it rains will produce leachate that seeps into the ground, causing soil and groundwater pollution. This wood waste can be used as activated carbon (adsorbent) for leachate treatment. The research was divided into two stages, namely adsorbent production and leachate treatment. Production of activated carbon from bark (bark) was activated using a solution of NaOH and H2SO4 as an activator, with variations of bark (gr): activator (ml) = 20:100; 50:200; 70:300. The leachate adsorption process used activated carbon with a mass of 2.5 and 5 g for 30, 60 and 120 minutes. The lowest adsorbent water content was 0.87% activated using NaOH, and the lowest ash content 0.79% when activated with H2SO4. This is still in accordance with the SII standard No.0258-88. The best variation occurred when the addition of activated carbon which was activated using 5 grams of H2SO4 for 120 minutes caused the most significant decrease in COD value of 52%, and pH 7.32. From the variations in the activation of activated carbon adsorbents, the activation of acidic solutions is better in leachate treatment.

The special mechanisms of quasi-complexation and enhanced effect of “·OH action zone” in activated carbon combined ozonation

Activated carbon (AC) is an excellent adsorbent and is widely employed as a catalyst in catalytic ozonation. However, the massive change in surface oxygen groups on AC before and after ozonation in this research indicated that AC was not a real catalyst. Moreover, the lower oxalic acid removal effect and the observed hydroxyl radicals (·OH) accumulative amount of pre-oxidative AC combined ozonation confirmed that AC functioned as an activator. We investigated the removal trend of oxalic acid in AC-activated ozonation under different pH, and it was consistent with its adsorption via adjusting the oxalic acid adsorbed on AC. Despite the accumulation concentration of ·OH reaching the highest value at pH = 4.7, the activated ozonation did not perform best. Considering the extremely short life of ·OH in an aqueous solution, an “action zone” existed, which was the effective region for ·OH to react with organics. This result proved that the AC adsorption would concentrate organics in the “action zone”, thus improving the degradation of organic contaminants. The solution containing oxalic acid had a higher accumulative concentration of ·OH than without oxalic acid, which meant a previously neglected pathway existed to produce ·OH. In addition, C2O4·- was reported in the solution containing AC, oxalic acid, and oxygen. Thus, the quasi-complexation reaction might occur between AC, oxalic acid, and oxygen. Overall, this study disclosed distinct mechanisms due to AC adsorption in the AC combined ozonation system.

The Effect of Variations in Methanol Concentration on the Esterification Process against Quality of Biodiesel from Used Cooking Oil

Used cooking oil has the potential to be used as raw material for biodiesel. However, the high Free Fatty Acid (FFA) content in used cooking oil can interfere with the transesterification process. This issue will affect the quality of biodiesel yields. Therefore, FFA content in used cooking oil must be reduced through a pre-treatment process by adding activated carbon adsorbent from charcoal. In this study, the adsorption process was carried out by mixing used cooking oil and activated carbon using 20% NaOH for 3 hours. Then the degumming process was carried out by adding 0.5% v/v HCl from the volume of used cooking oil. Then add 0.5% NaOH by weight of used cooking oil and distilled water gradually, accompanied by heating to a temperature of 120 °C. In the esterification stage, the variables used are the comparison of methanol with a ratio of 1: 2, 1: 4, 1: 6, 1: 8, and 1:10. In this study, the lower acid number obtained from all variables was 2,24 mg KOH/g sample. Meanwhile, the most optimal result was the 1: 2 variables with a density of 0.8531 g/ml, and the kinematic viscosity at 40°C was 4.94 mm2/s.

Comparison of activated carbon and low-cost adsorbents for removal of 2,4-dichlorophenol from wastewater using Aspen Adsorption and response surface methodology

ABSTRACT In this paper, the adsorption of the chlorinated organic compound, 2,4-dichlorophenol, using activated carbon (AC), bagasse fly ash (BFA) and rice husk fly ash (RHFA) in a packed bed column was simulated using Aspen Adsorption software. The purpose of this study was to demonstrate the effectiveness of simulation software for identifying alternative low-cost adsorbents and optimising the adsorption process. The effect of process parameters such as initial concentration, bed height and inlet feed flow rate were evaluated using breakthrough curves. It was shown that the longest breakthrough times were at a higher bed height of 3 m and lower flow rate of 2 m3/hr and concentration had no effect on breakthrough time. After optimisation using response surface methodology, the AC, BFA and RHFA had a breakthrough time of 534, 426 and 209 s, respectively. This shows the potential of BFA as a potential alternative for AC for the adsorption of 2,4-dichlorophenol and shows RHFA to be a relatively poor adsorbent in comparison. The economic evaluation illustrates that the overall cost of wastewater treatment with BFA and RHFA is lower than AC. The cost for the BFA and RHFA adsorbents is only a handling charge, but the cost for using AC adsorbent is £10,603/year. Therefore, the company can produce 17,520 m3/year of fresh water from the adsorbent and save £87,600/year. Therefore, it was concluded that BFA had a slightly weaker adsorption efficiency than AC but was more cost effective, allowing it to be more affordable and increasing its availability.

Modeling of adsorptive removal of azithromycin from aquatic media by CoFe2O4/NiO anchored microalgae-derived nitrogen-doped porous activated carbon adsorbent and colorimetric quantifying of azithromycin in pharmaceutical products

Herein, it was aimed to optimize the removal process of Azithromycin (Azi) from the aquatic environment via CoFe2O4/NiO nanoparticles anchored onto the microalgae-derived nitrogen-doped porous activated carbon (N-PAC), besides developing a colorimetric method for the swift monitoring of Azi in pharmaceutical products. In this study, the Spirulina platensis (Sp) was used as a biomass resource for fabricating CoFe2O4/NiO@N-PAC adsorbent. The pores of N-PAC mainly entail mesoporous structures with a mean pore diameter of 21.546 nm and total cavity volume (Vtotal) of 0.033578 cm3. g−1. The adsorption studies offered that 98.5% of Azi in aqueous media could remove by CoFe2O4/NiO@N-PAC. For the cyclic stability analysis, the adsorbent was separated magnetically and assessed at the end of five adsorption-desorption cycles with a negligible decrease in adsorption. The kinetic modeling revealed that the adsorption of Azi onto the CoFe2O4/NiO@N-PAC was well-fitted to the second-order reaction kinetics, and the highest adsorption capacity was found as 2000 mg. g−1 at 25 °C based on the Langmuir adsorption isotherm model at 0.8 g. L−1 adsorbent concentration. The Freundlich isotherm model had the best agreement with the experimental data. Thermodynamic modeling indicated the spontaneous and exothermic nature of the adsorption process. Moreover, the effects of pH, temperature, and operating time were also optimized in the colorimetric Azi detection. The blue ion-pair complexes between Azi and Coomassie Brilliant Blue G-250 (CBBG-250) reagent followed Beer's law at wavelengths of 640 nm in the concentration range of 1.0 μM to 1.0 mM with a 0.94 μM limit of detection (LOD). In addition, the selectivity of Azi determination was verified in presence of various species. Furthermore, the applicability of CBBG-250 dye for quantifying Azi was evaluated in Azi capsules as real samples, which revealed the acceptable recovery percentage (98.72–101.27%). This work paves the way for engineering advanced nanomaterials for the removal and monitoring of Azi and assures the sustainability of environmental protection and public health.

Process optimization and mechanism revealing of KMnO4 pre-oxidation coupled powdered activated carbon adsorption for 2-MIB removal

Taste and odor compounds such as 2-Methylisoborneol (2-MIB) have been a long-term challenge in drinking water treatment plants (DWTPs) and become increasingly concerning due to the implementation of stricter water quality regulations. The addition of powdered activated carbon (PAC) is one of the most effective approaches to control 2-MIB during cyanobacterial blooms. In this study, the process optimization of PAC adsorption and potassium permanganate (KMnO4) pre-oxidation was investigated and the mechanisms of the observed results were revealed. When the raw water was firstly pre-oxidized and subsequently treated by PAC, the adsorption of 2-MIB was not affected by the pre-oxidation, no matter whether the KMnO4 was depleted or remained. Even though the molecular weight distribution of the natural organic matter (NOM) was altered by the pre-oxidation, the trend of the NOM removal by pre-KMnO4/post-PAC was similar to that of the KMnO4 pre-oxidation, indicating that the KMnO4 did not affect the following PAC adsorption. When the raw water was added with PAC and KMnO4 simultaneously, the adsorption of 2-MIB decreased with the increase of KMnO4 dosage. The adsorption efficiency of NOM with smaller molecular weights (<3 kDa) decreased and that of NOM with larger molecular weights (>3 kDa) increased. It was found that the shrink of the micropore volume (but not surface functional groups) resulted in the negative effect on PAC by KMnO4. Therefore, the general recommendation to the DWTPs is that try to dose KMnO4 as early as possible so the remaining KMnO4 will not pose a negative effect on PAC for 2-MIB removal. Our study provides both practical guidance and theoretical fundamentals on the operation of DWTPs with KMnO4 pre-oxidation and PAC for 2-MIB removal.

Pre-treatment of waste cooking oil by combined activated carbon adsorption and acid esterification for biodiesel synthesis via two-stage transesterification

The abundance of waste cooking oil (WCO) makes it an attractive alternative for biodiesel production. To date, research emphasizing biodiesel production via two-step transesterification from WCO, with the pre-treatment of WCO using combined activated carbon adsorption and acid esterification, is limited. Therefore, it is the aim of this study to (1) reduce the free fatty acid of WCO through a combination of pre-treatment using activated carbon and esterification of acid catalysis simultaneously, (2) maximize the production of biodiesel via a two-step transesterification process, and (3) compare the converted biodiesel against the biodiesel standards. The amount of activated carbon and the reaction time for each step of the transesterification process are varied. The combination pre-treatment method has successfully reduced the FFA content in WCO from 9.297% to below 3%. The produced biodiesel is verified as fully converted biodiesel via solubility testing in ethanol. The optimum conditions for biodiesel production are pre-treatment using 5 g of powdered activated carbon and a reaction time for each transesterification step of 30 min. The biodiesel generated under these conditions meets the biodiesel standards. It has the highest content of saturated fatty acid, with the maximum biodiesel yield of 52.78%.

Correction to: Treatment of wastewater from food waste hydrothermal carbonization via Fenton oxidization combined activated carbon adsorption

Correction to: Treatment of wastewater from food waste hydrothermal carbonization via Fenton oxidization combined activated carbon adsorption