PVC-induced chlorine-bromine exchange in the pyrolysis of polybrominated diphenyl ethers, -biphenyls, -dibenzodioxins and dibenzofurans

Extensive chlorine-for-bromine exchange occurs when 1,2,3,4-tetrabromodibenzodioxin (TBrDD), polybromodibenzodioxin/furan mixtures (PBrDD/F), and technical brominated diphenyl ethers and -biphenyls are pyrolyzed at 800°C in the presence of PVC. Tetra-ClDD, BrCl₃DD, Br₂Cl₂DD, and Br₃ClDD could be detected from the pyrolysis of 1,2,3,4-TBrDD. A number of chloro/bromodibenzodioxins and furans as well as chlorinated dibenzodioxins and furans are formed in the residues of the PBrDD/F mixtures. Only chlorinated and chlorinated/brominated diphenyl ethers and no dioxins and furans occured during the pyrolysis of brominated diphenyl ethers in the presence of PVC. Through the exchange of bromine with chlorine, chlorinated and chlorinated/brominated biphenyls could be detected from the pyrolysates of hexabromobiphenyl.     

Chlorine-bromine exchange during pyrolysis of 1,2,3,4-tetrabromo-dibenzodioxin with various chlorine donors

1,2,3,4-T₄BrDD was pyrolyzed with PVC, HCl and NaCl at 900°C. In all reactions bromine was exchanged with chlorine. During the pyrolysis with PVC at T = 900°C, 69 % of the starting material reacted to give BrCl-dioxins (34.3 %) and 1,2,3,4-T₄CDD (34.7 %). In the reaction with HCl (T = 900°C), 49.2 % BrCl-dioxins and 1,2,3,4-T₄CDD formed. The pyrolysis with NaCl (T = 900°C) yielded 10.5 % BrCl-dioxins and 1,2,3,4-T₄CDD.     

Pyrolysis and GC/MS-analysis of brominated flame retardants in on-line operation

Flame retardants such as brominated diphenyl ethers (Bromkal 70-5-DE, FR 300 BA), 2,4,6-tribromophenol, pentabromophenol and hexabromobiphenyl were pyrolyzed at 600°C, 700°C, 800°C and 900°C in absence of oxygen in a SGE pyrojector, and the residues were analyzed by means of GC/MS in on-line operation. The pyrolysis of Bromkal 70-5-DE hereby yielded bromobenzenes (PBBz), bromophenols (PBP) and brominated dibenzofurans (PBDF). PBBz, bromonaphthalenes (PBN) and PBDF could be detected in the FR 300 BA pyrolysate, whereas brominated benzenes and dibenzodioxins formed during the pyrolysis of 2,4,6-tribromophenol. Unlike the pyrolysis of 2,4,6-tribromophenol, pentabromophenol pyrolysis produced mainly bromobenzenes along with traces of bromonaphthalenes, bromodioxins and bromodiphenyl ethers. The pyrogram of hexabromobiphenyl showed bromobenzenes and brominated biphenyls as key pyrolysate components.     

Bildung von 2,3,7,8-TCDD bei der Thermolyse von ausgewählten chlorierten organischen Verbindungen

Upon heating of 2,4,5-T to 600°C, 2,3,7,8-TCDD is formed with a yield of 0,2 %. At 800°C, the formation of TCDD decreases by a factor at 200. Tormona 80^® an ester at 2,4,5-T yields 200 ppm TCDD at 600°C and 3 ppm at 800°C. The highest formation rate is observed for 2,4,5-Trichlorophenol (0,5 % at 600°C). During the thermolysis of 2,4-D, γ-Hexachlorocyclohexane, 2,4,6-Trichlorophenol, Pentachlorophenol and Clophen A 40. 2,3,7,8-TCDD could not be detected.     

Chlorination of bisphenol A in aqueous media: formation of chlorinated bisphenol A congeners and degradation to chlorinated phenolic compounds

The chlorination of bisphenol A (BPA) in aqueous media was investigated in order to describe the degradation profile of this compound and the formation of chlorinated products. Aqueous solutions of BPA (approx. 1 mg/l) were chlorinated by sodium hypochlorite solution at room temperature and under weakly alkaline conditions. Chlorinated compounds were extracted with dichloromethane and determined by gas chromatography/mass spectrometry (GC/MS). BPA was consumed completely within 5 min of chlorination, when the initial chlorine concentration was 10.24 mg/l (molar ratio to BPA, 58.7). On the other hand, when the initial chlorine concentration was 1.03 mg/l (molar ratio, 6.56), 9.3% of BPA still remained after 60 min chlorination. Five chlorinated BPA congeners, 2-chlorobisphenol A (MCBPA), 2,6-dichlorobisphenol A (2,6-D2CBPA), 2,2'-dichlorobisphenol A (2,2'-D2CBPA), 2,2',6-trichlorobisphenol A (T3CBPA) and 2,2', 6,6'-tetrachlorobisphenol A (T4CBPA) were formed in the earlier stages of chlorination. Several chlorinated phenolic compounds, 2,4,6-trichlorophenol (T3CP), 2,6-dichloro-1,4-benzoquinone (D2CBQ), 2,6-dichloro-1,4-hydroquinone (D2CHQ), C9H10Cl2O2, C9H8Cl2O and C10H12Cl2O2, were also formed by further chlorination.     

Differences between 4-fluoroaniline degradation and autoinducer release by Acinetobacter sp. TW: implications for operating conditions in bacterial bioaugmentation

To develop a bacterial bioaugmentation system for fluorine-containing industrial wastewater treatment, optimal conditions for 4-fluoroaniline (4-FA) degradation and autoinducer release in Acinetobacter sp. TW were determined. Quorum sensing in biofilms of strain TW was also investigated. Different optimal conditions exist for 4-FA degradation and autoinducer release, particularly with regard to pH. Quorum sensing modulates extracellular polymeric substance (EPS) secretion and biofilm formation in the strain but plays no role in 4-FA degradation. Under optimal conditions for 4-FA degradation, the release of N-3-oxo-hexanoyl-homoserine lactone (3-oxo-C₆-HSL) and N-hexanoyl-homoserine lactone (C₆-HSL) in strain TW was significantly lower than required for quorum sensing. Under optimal conditions for autoinducer release, on the other hand, 3-oxo-C₆-HSL and C₆-HSL levels exceeded the quorum sensing thresholds, thereby inducing EPS secretion and biofilm formation. We conclude that the optimal conditions for autoinducer release (25 °C, pH 5, 800 mg L^?1 4-FA, and 0 % NaCl) are suitable for bacterial colonization in bioaugmentation, while those for 4-FA degradation (25–30 °C, pH 8 and 800 mg L^?1 4-FA) maximize the system performance after colonization.     

Electrochemical oxidation of bisphenol A. Application to the removal of bisphenol A using a carbon fiber electrode

Leachate samples with a high strength of ammonium-nitrogen (NH4+-N) were collected from a local landfill site in Hong Kong. Two experiments were carried out to study (1) the inhibition of microbial activity of activated sludge by NH4+-N and (2) the chemical precipitation of NH4+-N from leachate as a preliminary treatment prior to the activated sludge process. The experimental results demonstrated that the efficiency of COD removal decreased from 97.7% to 78.1%, and the dehydrogenase activity of activated sludge decreased from 9.29 to 4.93 microg TF/mg MLSS, respectively, when the NH4+-N concentration increased from 53 to 800 mg/l. The experiment also demonstrated that the NH4+-N in the leachate can be quickly precipitated as MgNH4PO4 x 6H2O after addition of MgCl2 x 6H2O + Na2HPO4 x 12H2O. The NH4+-N concentration was reduced from 5618 to 112 mg/l within 15 min when a molar ratio of Mg2+:NH+:PO4(3-) = 1:1:1 was used. The optimum pH to reach the minimum solubility of MgNH4PO4 x 6H2O was found to be in the range of 8.5-9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl2 x 6H2O + Na2HPO4 x 12H2O, which may affect microbial activity in the following biological treatment processes. Using two other combinations of chemicals [MgO + 85%H3PO4 and Ca(H2PO4)2 x H2O + MgSO4 x 7H2O] could minimise salinity generation after precipitation, while they were less efficient for NH4+-N removal.     

Effect of UV radiation and temperature on mineralization and volatilization of coumaphos in water

This study was undertaken to determine the dissipation and degradation of coumaphos [O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate] under different sunlight conditions and at different temperatures. The effect of the ultra violet (UV) component of solar radiation was also studied using quartz tubes in addition to other radiation in the visible range using glass tubes and the results were compared with those obtained under the dark light conditions. Water suspensions of coumaphos were incubated at three temperatures viz. 22°C, 37°C and 53°C in closed systems to study the effect of temperature. Volatilization, mineralization and degradation of coumaphos increased with an increase in temperature and exposure to solar radiation, particularly under the UV component of the solar radiation. Major loss of the pesticide occurred through volatilization. The optimum temperature for the degradation of coumaphos was found to be at 37°C. The data obtained from the mineralization and degradation studies indicated that 53°C crosses the biological range for suitable growth of microorganism. UV radiation exposure along with maintaining temperature at 37°C may prove useful in the dissipation and/or degradation of coumaphos prior to its disposal as waste from cattle dipping vats.     

Bio-optimization of the carbon-to-nitrogen ratio for efficient vermicomposting of chicken manure and waste paper using <Emphasis Type="Italic">Eisenia fetida</Emphasis>

The main objective of the present study was to determine the optimum C/N ratio for converting waste paper and chicken manure to nutrient-rich manure with minimum toxicity. Six treatments of C/N ratio 20, 30, 40, 50, 60, and 70 (T1, T2, T3, T4, T5, and T6, respectively) achieved by mixing chicken manure with shredded paper were used. The study involved a composting stage for 20 days followed by vermicomposting with Eisenia fetida for 7 weeks. The results revealed that 20 days of composting considerably degraded the organic waste mixtures from all treatments and a further 7 weeks of vermiculture significantly improved the bioconversion and nutrient value of all treatments. The C/N ratio of 40 (T3) resulted in the best quality vermicompost compared to the other treatments. Earthworm biomass was highest at T3 and T4 possibly due to a greater reduction of toxic substances in these waste mixtures. The total N, total P, and total K concentrations increased with time while total carbon, C/N ratio, electrical conductivity (EC), and heavy metal content gradually decreased with time during the vermicomposting process. Scanning electron microscopy (SEM) revealed the intrastructural degradation of the chicken manure and shredded paper matrix which confirmed the extent of biodegradation of treatment mixtures as result of the composting and vermicomposting processes. Phytotoxicity evaluation of final vermicomposts using tomato (Lycopersicon esculentum), radish (Raphanus sativus), carrot (Daucus carota), and onion (Allium cepa) as test crops showed the non-phytotoxicity of the vermicomposts to be in the order T3 > T4 > T2 > T1 > T5 > T6. Generally, the results indicated that the combination of composting and vermicomposting processes is a good strategy for the management of chicken manure/paper waste mixtures and that the ideal C/N ratio of the waste mixture is 40 (T3).     

Combustion experiments using pentachlorophenol on a pilot scale and full-scale

Chlorinated phenols are used at many saw mills for impregnation of saw timber. Waste products containing the used compound follow this process. Tests have been performed on pilot and full-scale in order to investigate the possibility of destroying these wastes by combustion.The pilot scale tests with 70 g of pentachlorophenol show that at a transit time of approximately 3 seconds and a combustion temperature of 600°C the unburnt residue was 50 mg/kg fed in pentachlorophenol. At 800°C the residue decreased to 15 mg/kg. No formation of octachlorodioxin could be proved.The full-scale test with a small amount of pentachlorophenol and a large amount of tetrachlorophenol show that at a transit time of approximately 0.9 seconds and a temperature varying during one test between 620–875° (average 760°C), the unburnt residue was 9 mg/kg for tetrachlorophenol and 650 mg/kg for pentachlorophenol. At an increased load the residue increased gradually, being 5.900 mg/kg for tetrachlorophenol and 7.100 mg/kg for pentachlorophenol at a test when the temperature was varied between 460 and 850° (average 620°C). Analyses of chlorinated dioxins show that octachlorodioxin was found in the flue gas at one of the tests. This may indicate a formation.     

Comparison of particle emissions from small heavy fuel oil and wood-fired boilers

Flue gas emissions of wood and heavy fuel oil (HFO) fired district heating units of size range 4–15 MW were studied. The emission measurements included analyses of particle mass, number and size distributions, particle chemical compositions and gaseous emissions. Thermodynamic equilibrium calculations were carried out to interpret the experimental findings.In wood combustion, PM1 (fine particle emission) was mainly formed of K, S and Cl, released from the fuel. In addition PM1 contained small amounts of organic material, CO₃, Na and different metals of which Zn was the most abundant. The fine particles from HFO combustion contained varying transient metals and Na that originate from the fuel, sulphuric acid, elemental carbon (soot) and organic material. The majority of particles were formed at high temperature (>800 °C) from V, Ni, Fe and Na. At the flue gas dew point (125 °C in undiluted flue gas) sulphuric acid condensed forming a liquid layer on the particles. This increases the PM1 substantially and may lead to partial dissolution of the metallic cores.Wood-fired grate boilers had 6–21-fold PM1 and 2–23-fold total suspended particle (TSP) concentrations upstream of the particle filters when compared to those of HFO-fired boilers. However, the use of single field electrostatic precipitators (ESP) in wood-fired grate boilers decreased particle emissions to same level or even lower as in HFO combustion. On the other hand, particles released from the HFO boilers were clearly smaller and higher in number concentration than those of wood boilers with ESPs. In addition, in contrast to wood combustion, HFO boilers produce notable SO₂ emissions that contribute to secondary particle formation in the atmosphere. Due to vast differences in concentrations of gaseous and particle emissions and in the physical and chemical properties of the particles, HFO and wood fuel based energy production units are likely to have very different effects on health and climate.     

Uptake,depuration and biotransformation of anthracene by the scud Pontoporeia hoyi

Uptake, depuration and biotransformation rates of ¹⁴C-anthracene were determined for Pontoporeia hoyi, the dominant benthic invertebrate in the Great Lakes, at 4°, 7°, 10° and 15°C. The uptake rate constants for anthracene increased from 136±22 h^?1 (n=4, $\text{X}\text{?}\text{±1}\text{SD}$) to 215±45 h^?1 (n=4) over the temperature range studied and were seasonally dependent. The depuration rate constant at the apparent optimum temperature of 7°C was 0.015 h^?1 for anthracene. The biotransformation ability of P. hoyi is low, and degradation of anthracene was undetectable even after exposures of 48 h. The bioconcentration factor can be predicted from the uptake and depuration kinetics to be approximately 16,800 at 4°C. These experiments imply that P. hoyi may be very important in food chain biomagnification of some toxic organics.     

Bioavailability and dissipation of fluridone under controlled conditions

Abstract

Bioavailability of fluridone, l‐methyl‐3‐phenyl‐5‐[3‐(trifluoromethyl) phenyl]‐4(1H)‐pyridinone, as affected by soil temperature, soil moisture regime, and duration of incubation was investigated in three soil types by grain sorghum (Sorghum bicolor [L.] Moench cv. Abu Sabien) chlorophyll bioassay. Initial loss of fluridone was rapid and dissipation followed first‐order kinetics under most of the incubation treatments investigated. Soil moisture, in general, had a greater impact than soil temperature on dissipation of fluridone. The herbicide dissipated faster at the fluctuating room temperature (18–24°C) than at the constant 10°C in Sonning sandy clay loam (O.M. = 1.2%) and Erl Wood sandy loam (O.M. = 2.5%) but not in Shropshire loamy peat (O.M. = 33%). In the two mineral soils, bioassay‐detectable residues from an initial rate of 1.00 μg/g were least (0.00 ‐ 0.10 μg/g) at 1/2 field capacity (FC) and greatest (0.16 ‐ 0.37 μg/g) at 1/4 FC, 400 days after treatment. At 10°C, the DT₅₀ values (days) at 1/4 FC and 1/2 FC were, respectively, 147 ± 16 and 69 ± 6 for Erl Wood soil, and 257 ± 28 and 51 ± 12 for Sonning soil. In Shropshire soil, concentrations of bioavailable fluridone were least at each bioassay date when soil moisture was maintained at FC, at both temperatures of incubation. At 10°C, herbicide concentrations in the organic soil from an initial rate of 10.00 μg/g were 0.95 and 4.69 μg/g, respectively, at FC and 1/4 FC.     

Numerical simulation of the thermal destruction of some chlorinated C1 and C2 hydrocarbons

We have numerically modeled the breakdown of small quantities of several chlorinated hydrocarbons (CH3Cl, CH2Cl2, CHCl3, CCl4, C2H3Cl, and C2H5Cl) in a lean mixture of combustion products between 800 and 1480 K. This simulates the fate of poorly atomized waste in a liquid-injection incinerator. Kinetics calculations were performed using the CHEMKIN and SENKIN programs, with a reaction mechanism that was developed at Louisiana State University to model flat-flame burner experiments. A 99.99-percent destruction efficiency was attained in one second at temperatures ranging from 1280 to 960 K, with CCl4 requiring the highest temperature for destruction and C2H5Cl the lowest. For all compounds except C2H5Cl, there was a range of temperatures at which byproducts accounted for several percent of the elemental chlorine at the outlet. The more heavily chlorinated compounds formed more byproducts even though the amount of elemental chlorine was the same in all cases. The sensitivity of results to residence time, equivalence ratio, temperature profile, and the presence of additional chlorine, was examined for the case of CHCl3.     

Modeling adsorption kinetics of trichloroethylene onto biochars derived from soybean stover and peanut shell wastes

Trichloroethylene (TCE) is one of the most hazardous organic pollutants in groundwater. Biochar produced from agricultural waste materials could serve as a novel carbonaceous adsorbent for removing organic contaminants from aqueous media. Biochars derived from pyrolysis of soybean stover at 300 °C and 700 °C (S-300 and S-700, respectively), and peanut shells at 300 °C and 700 °C (P-300 and P-700, respectively) were utilized as carbonaceous adsorbents to study batch aqueous TCE remediation kinetics. Different rate-based and diffusion-based kinetic models were adopted to understand the TCE adsorption mechanism on biochars. With an equilibrium time of 8–10 h, up to 69 % TCE was removed from water. Biochars produced at 700 °C were more effective than those produced at 300 °C. The P-700 and S-700 had lower molar H/C and O/C versus P-300 and S-300 resulting in high aromaticity and low polarity accompanying with high surface area and high adsorption capacity. The pseudo-second order and intraparticle diffusion models were well fitted to the kinetic data, thereby, indicating that chemisorption and pore diffusion were the dominating mechanisms of TCE adsorption onto biochars.     

Adsorption of chloridazon from aqueous solution on modified kerolite-rich materials

The adsorption of chloridazon (5-amine-4-chloro-2-phenylpyridazin-3(2H)-one) on kerolite samples heated at 110°C (K-110), 200°C (K-200), 400°C (K-400), 600°C (K-600) and acid-treated with H₂SO₄ solutions of two different concentrations (0.25 and 0.5 M) (K-0.25 and K-0.5, respectively) from pure water at 25°C has been studied by using batch and column experiments. The adsorption experimental data points were fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f) of the samples; K_f values ranged from 184.7 mg kg^?1 (K-0.5) up to 2253 mg kg^?1 (K-600). This indicated that the heat treatment given to the kerolite greatly increases its adsorption capacity for the herbicide whereas the acid treatment produces a clear decrease in the amount of chloridazon adsorbed. The removal efficiency (R) was also calculated; R values ranging from 52.8% (K-0.5) up to 88.3% (K-600). Thus, the results showed that the 600°C heat-treated kerolite was more effective in relation to adsorption of chloridazon and it might be reasonably used in removing this herbicide from water.     

Primary product distribution from the Cl-atom initiated atmospheric degradation of furan: Environmental implications

Furan is an aromatic hydrocarbon present in both urban and rural atmospheres, which is emitted mainly by biomass burning and the combustion of fossil fuel. Reaction of furan and Cl atoms may be important in areas where chlorine atom concentrations are potentially high such as marine and coastal regions or continental atmospheres where industrial activity emits molecular chlorine or photo-labile Cl-containing compounds. To assess the importance of this reaction and to investigate whether any unique chlorine-containing product is formed the products of the reaction of Cl atoms with furan have been determined under atmospheric conditions. For the study two different sampling/detection methods have been used: (1) Solid-Phase MicroExtraction, with subsequent analysis by thermal desorption, and gas chromatography with mass spectrometry or flame ionization detection (SPME/GC-MS/FID), and 2-“in situ” with long path fourier transform infrared spectroscopy (FTIR). The yields of primary reaction products in the absence of NO were: 5-chloro-2(5H)-furanone (64.5±10.7)%, E-butenedial (11±3)%, 5-hydroxy-2(5H)-furanone (⩽2.4%) and Z-butenedial (1.6±0.5)%. Other products generated by secondary reactions were 2(3H)-furanone (2.8±1.9)%, HCl (21.1±3%) and CO. Maleic anhydride was detected with a yield of about 2%, however, this yield may be a combination of both primary and secondary reactions. All errors are ±2σ. The observed products confirm that addition of Cl atoms to the double bond of furan is the dominant reaction pathway.     

Simultaneous determination of estrogenic odorant alkylphenols,chlorophenols, and their derivatives in water using online headspace solid phase microextraction coupled with gas chromatography-mass spectrometry

A simple online headspace solid-phase microextraction (HS-SPME) coupled with the gas chromatography-mass spectrometry (GC-MS) method was developed for simultaneous determination of trace amounts of nine estrogenic odorant alkylphenols and chlorophenols and their derivatives in water samples. The extraction conditions of HS-SPME were optimized including fiber selection, extraction temperature, extraction time, and salt concentration. Results showed that divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was the most appropriate one among the three selected commercial fibers, and the optimal extraction temperature, time, and salt concentration were 70 °C, 30 min, and 0.25 g/mL, respectively. The developed method was validated and showed good linearity (R ²?>?0.989), low limit of detection (LOD, 0.002–0.5 μg/L), and excellent recoveries (76–126 %) with low relative standard deviation (RSD, 0.7–12.9 %). The developed method was finally applied to two surface water samples and some of these target compounds were detected. All these detected compounds were below their odor thresholds, except for 2,4,6-TCAS and 2,4,6-TBAS wherein their concentrations were near their odor thresholds. However, in the two surface water samples, these detected compounds contributed to a certain amount of estrogenicity, which seemed to suggest that more attention should be paid to the issue of estrogenicity rather than to the odor problem.     

Identification of highly brominated analogues of Q1 in marine mammals

Three novel halogenated organic compounds (HOCs) have been identified in the blubber of marine mammals from coastal New England with the molecular formulae C(9)H(3)N(2)Br(6)Cl, C(9)H(3)N(2)Br(7), and C(9)H(4)N(2)Br(5)Cl. They were identified using high and low resolution gas chromatography mass spectrometry (GCMS) and appear to be highly brominated analogues of Q1, a heptachlorinated HOC suspected to be naturally produced. These compounds were found in Atlantic white sided dolphin (Lagenorhynchus acutus), bottlenose dolphin (Tursiops truncatus), common dolphin (Delphinus delphis), Risso's dolphin (Grampus griseus), harbor porpoise (Phocoena phocoena), beluga whale (Delphinapterus leucas), fin whale (Balaenoptera physalus), grey seal (Halichoerus grypus), harp seal (Phoca groenlandica) and a potential food source (Loligo pealei) with concentrations as high as 2.7 microg/g (lipid weight). The regiospecificity of C(9)H(3)N(2)Br(6)Cl is suggestive of a biogenic origin. Debromination of C(9)H(3)N(2)Br(6)Cl may be significant in the formation of C(9)H(4)N(2)Br(5)Cl.     

Preparation and characterisation of activated carbon from waste tea by physical activation using steam

ABSTRACT

In this study, the feasibility of preparing activated carbon from waste tea by physical activation using steam was investigated. The effects of activation temperature on yield and pore properties of the prepared activated carbon were studied. The yield decreased with increased activation temperature owing to the decomposition of cellulose and hemicellulose. The specific surface area and pore volume of the activated carbon were estimated using the Brunauer–Emmett–Teller method, Langmuir equation, and t-plot method. The specific surface area and micropore volume increased with increases in activation temperature, as additional volatile materials were released. The specific surface area significantly decreased at first but slightly increased with increasing activation time. The maximum specific surface area reached 995 m²/g at an activation temperature of 800 °C with a water flow rate of 0.075 g/min and a constant hold time of 0.5 hr. According to the nitrogen adsorption isotherms, micropores mainly developed when the activation temperature was below 800 °C, and both micropores and mesopores developed when it was above 800 °C. The results showed that activation temperature significantly affected micropore and mesopore volumes, as well as the specific surface area of the activated carbon. Overall, waste tea was found to be an attractive raw material for producing low-cost activated carbon.

Implications: Every year, a large amount of waste tea is generated after extraction. The high carbon content of waste tea showed that it can be used as raw material to produce activated carbon. This study investigated the feasibility of preparing activated carbon from waste tea by physical activation using steam. Temperature and time were found to have clear effects on pore properties. Our proposed method and raw material are more environmentally friendly and involve low cost. Furthermore, this offers a potential solution to the problems of waste tea disposal and low-cost activated carbon production.