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This study systematically investigated the photocatalytic activity of dissolved state biochar (DSB) with different pyrolysis temperature to the degradation of atorvastatin (ATV), a medicine widely used to combat hyperlipidemia. It was found that the photocatalytic efficiency of DSB increased with the decrease of pyrolysis temperature, that is, DSB300 (DSB with 300 °C of pyrolysis temperature) had the greatest photocatalytic activity in same condition, which was attributed to the dual role of DSB300 as heterogeneous photocatalyst and photosensitizer. The mineral components were responsible for the heterogeneous photocatalytic activity of DSB300. Organic carbon components could synergistically enhance the heterogeneous photocatalytic activity by enhancement of electron-hole separation, and contribute to the formation of singlet oxygen ( 1 O 2 ) and triplet-excited state ( 3 DSB*) as well. The identification of intermediate products and X-ray photoelectron spectroscopy (XPS) analysis of irradiated DSB300/ATV revealed that cross-coupling reaction between ATV and DSB existed in the photodegradation process of ATV. The detailed photodegradation pathways of ATV were proposed, which was triggered by oxygen insertion of pyrrole ring and hydroxyl addition. Meanwhile, the modification of DSB300 under irradiation was evidently attenuated with ATV as shown by multiple characterizations, which helped to keep the stability of DSB300 in photochemical reaction process., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this work, a novel, economical and effective vessel-like biochar-based photocatalyst Bi 2 S 3 /BiOBr/BC was synthesized by a facile one-pot solvothermal method for the first time. A series of characterization analyses demonstrated the successful preparation of photocatalyst Bi 2 S 3 /BiOBr/BC. Furthermore, diclofenac (DCF) as the target contaminant was applied to elucidate the enhanced photocatalytic performance (93.65%, 40 min) under energy-saving visible LED light irradiation. Comparison experiments among different photocatalysts and photoelectrochemical tests results illustrated that excellent photocatalytic performance of Bi 2 S 3 /BiOBr/BC 10% might be attributed to the electrons transfer of biochar and higher charge separation efficiency of heterojunction structure. Besides, lower electrical energy per order value indicated photocatalyst/visible LED light system was more energy-saving. Proper photocatalyst dosage (0.6 g/L) and relatively acidic water environment (pH = 5.0) would be beneficial to DCF photodegrdation by Bi 2 S 3 /BiOBr/BC. Good reusability and stability of Bi 2 S 3 /BiOBr/BC were verified via five consecutive recycle experiments. Furthermore, the role of active species was determined through trapping experiments and O 2 - and h + dominated the photodegradation reaction to mineralize DCF molecules. Eleven main intermediates and four possible photodegradation pathways were proposed by HRMS analysis. Accordingly, photocatalyst Bi 2 S 3 /BiOBr/BC would provide potential technical support for emerging pollutant removal in water matrix., Competing Interests: Declaration of Competing Interest All authors declare that there are no competing interests, financial or otherwise, and approve to submit to Journal of Hazardous Materials., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The aim of the present study was to investigate the photocatalytic performance of biochar (BC)-incorporated Zn-Co-layered double hydroxide (LDH) nanostructures in gemifloxacin (GMF) degradation as a model pharmaceutical pollutant. The as-prepared Zn-Co-LDH@BC showed high photocatalytic efficiency due to the enhanced separation of photo-generated charge carriers using cobalt hydroxide as well as inhibiting the agglomeration of LDH nanostructures by incorporation of BC. According to the results, 92.7% of GMF was degraded through photocatalysis in the presence of Zn-Co-LDH catalyst. The photocatalytic performance of BC-incorporated Zn-Co-LDH was highly dependent on the solute concentration and photocatalyst dosage. The addition of ethanol caused more inhibiting effect than that of benzoquinone (BQ), indicating the major role of • OH in decomposition of GMF compared to the negligible role of O 2 •- . A greater enhancement in the photocatalytic degradation of GMF was obtained when the photoreactor containing Zn-Co-LDH@BC nanostructures was oxygenated. Less than 10% drop in the removal efficiency of GMF was observed within five successive operational runs. The results of chemical oxygen demand (COD) analysis indicated the COD removal efficiency of about 80% within 200 min, indicating the acceptable mineralization of GMF. The reaction pathways were also proposed for the photocatalytic conversion of GMF under UV light irradiation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study was conducted to understand the effects of ultraviolet (UV) irradiation on the physicochemical properties and the hexavalent chromium (Cr(VI)) removal ability of biochar. Structural and morphological analysis showed that UV irradiation increased the specific surface area of biochar and added a large amount of oxygen-containing functional groups (e.g., carboxyl, lactonic, and hydroxyl) to biochar's surface. Batch sorption experimental results showed that UV-modified biochar (UVBC) produced at the pyrolysis temperature of 300 °C, the irradiated time of 24 h, and the irradiation distance of 40 mm exhibited excellent Cr(VI) removal ability (from 1.11 mg/g for BC to 20.04 mg/g for UVBC, a 18.1-fold increase). The adsorption kinetics and adsorption isotherm data agreed well with the pseudo-second-order model and Freundlich model, respectively. Experimental and modeling results suggest that the oxygen-containing functional groups and specific surface areas of biochars were notably increased by UV irradiation, which enhanced Cr(VI) adsorption by surface complexation. X-ray photoelectron spectroscopy (XPS) analysis of UVBC before and after reaction with Cr(VI) showed that reduction occurred during Cr(VI) adsorption. The energy consumption of UV modification is 2.7 MJ per gram of UVBC produced, which is comparable to that in activated carbon. The results showed that the method of UV modification of biochar is a very novel and effective method for the adsorption of Cr(VI) in solution.

To decrease the secondary pollution of volatile organic compounds (VOCs) during adsorbent regeneration by microwave, electrodeless lamp was added in the microwave field to oxidize VOCs in the gas phase. Ultraviolet has a significant improvement on mineralization of VOCs generated from adsorbate during adsorbent regeneration. However, the mechanism and main influence factors on the degradation of VOCs are not clear. The effect of microwave power, regeneration time, airflow rate, and humidity content on the mineralization of adsorbed tetracycline during adsorbent regeneration was studied. Ozone concentration and ultraviolet irradiation intensity were also measured to analyze the mechanism of the microwave-ultraviolet adsorbent regeneration method. Although the electrodeless lamp adsorbed microwave and competed with the regenerated adsorbent, the mineralization percentage of tetracycline increased about 10% with the presence of electrodeless lamp at the same microwave power supply. Besides, humidity content also takes an important role on enhancing the mineralization of tetracycline. The mineralization of tetracycline in the microwave-ultraviolet field consists of three major parts: pyrolysis, ozone oxidation, and free radical oxidation. More than 50% adsorbed tetracycline can be oxidized into H 2 O and CO 2 during regeneration in 5 min. These results support the potential use of electrodeless lamp to treat VOCs in the gas phase to decrease the risk of secondary pollution during adsorbent regeneration.

Coconut shell based biochar was modified by ultraviolet irradiation with UV light at a wavelength of 365 nm in order to enhance the adsorption capacity for volatile organic compounds (VOCs). The breakthrough curves of biochars for adsorbing two typical VOCs (benzene and toluene) were examined. The results showed that the adsorption capacity of modified biochar was greatly increased. The saturation adsorption capacity of modified biochar for benzene and toluene was increased to 122.80 mg·g -1 and 236.36 mg·g -1 , comparing to that of the pristine biochar (7.27 mg·g -1 and 7.98 mg·g -1 , respectively). The breakthrough time of modified biochar for benzene and toluene (390 min and 620 min) was also drastically prolonged as compared to the raw biochar (1 min and 2 min). The characterization analysis of biochars suggested that the carboxylic groups and external surface area were largely enriched, which might be the main factor responsible for the enhanced adsorption of the two VOCs on the modified biochar. The processes of adsorbing benzene and toluene at different concentrations on modified biochar were fitted by Yoon-Nelson, Thomas and BDST models. The result demonstrated that these three models could provide good fitting and the correlation coefficients were all above 0.992. The TG-DTG result proved that ultraviolet irradiation had little effect on the thermal stability of biochar. The modified biochar after adsorption saturation could be reused after thermal regeneration and the regenerated char also had high adsorption capacity after five times of repeated utilization.

A new method of ultraviolet light (UV) activated persulfate (PS) oxidation was investigated to regenerate granular activated carbon (GAC) in drinking water applications. The improvements in iodine and methylene blue numbers measured in the GAC after ultraviolet- (UV) activated persulfate suggested that the GAC preloaded with natural organic matter (NOM) was chemically regenerated. An experimental matrix for UV-activated persulfate regeneration included a range of persulfate doses and different UV wavelengths. Over 87% of the initial iodine number for GAC was restored under the optimum conditions, perfulfate dosage 60 g/L and UV exposure 1.75 × 10(4) mJ/cm(2). The persulfate dosages had little effect on the recovery of the methylene blue number, which was approximately 65%. Persulfate activation at 185 nm was superior to activation at 254 nm. UV activation of persulfate in the presence of GAC produced acid, lowering the solution pH. Higher persulfate concentrations and UV exposure resulted in greater GAC regeneration. Typical organic and inorganic byproducts (e.g., benzene compounds and sulfate ions) were measured as a component of treated water quality safety. This study provides a proof-of-concept that can be used to optimize pilot-scale and full-scale UV-activated persulfate for regeneration of NOM-saturated GAC., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A sequential adsorption/photocatalytic regeneration process to remove tartrazine, an azo-dye in aqueous solution, has been investigated. The aim ofthis work was to compare the effectiveness of an adsorbent/photocatalyst composite-TiO2 deposited onto activated carbon (AC) - and a simple mixture of powders of TiO2 and AC in same proportion. The composite was an innovative material as the photocatalyst, TiO2, was deposited on the porous surface ofa microporous-AC using metal-organic chemical vapour deposition in fluidized bed. The sequential process was composed of two-batch step cycles: every cycle alternated a step of adsorption and a step of photocatalytic oxidation under ultra-violet (365 nm), at 25 degreeC and atmospheric pressure. Both steps, adsorption and photocatalytic oxidation, have been investigated during four cycles. For both materials, the cumulated amounts adsorbed during four cycles corresponded to nearly twice the maximum adsorption capacities qmax proving the photocatalytic oxidation to regenerate the adsorbent. Concerning photocatalytic oxidation, the degree of mineralization was higher with the TiO2/AC composite: for each cycle, the value of the total organic carbon removal was 25% higher than that obtained with the mixture powder. These better photocatalytic performances involved better regeneration than higher adsorbed amounts for cycles 2, 3 and 4. Better performances with this promising material - TiO2 deposited onto AC - compared with TiO2 powder could be explained by the vicinity of photocatalytic and AC adsorption sites.

The aim of this paper was to investigate the feasibility of using gamma irradiation to inhibit the microbial activity of biological powder activated carbon (PAC) without impacting its adsorptive properties. First of all, the range of dose of gamma rays required to produce abiotic PAC was selected on the basis of heterotrophic plate counts (HPC) inactivation and methylene blue (MB) adsorption kinetics. Doses inferior to 10 kGy were not sufficient to inhibit the culture of heterotrophic bacteria. On the other hand, doses superior to 15 kGy were demonstrated to affect the adsorption rate of MB. Consequently, a dose comprised between 10 and 15 kGy was selected for further investigation. In order to validate the adequacy of the range of dose (i.e. 10-15 kGy), adsorption characteristics were tested by monitoring the removal kinetics of refractory dissolved organic carbon (RDOC). No significant differences were observed between irradiated and non-irradiated biological PAC for the adsorption of RDOC. Irradiated, non-irradiated and virgin PAC were also evaluated in terms of abundance of viable (using the LIVE/DEAD BacLight method) bacteria and in terms of heterotrophic biomass activity. The results of the BacLight method demonstrated that attachment of the biofilm on the PAC was not impacted by the irradiation and heterotrophic activity measurements demonstrated that the latter could be radically reduced in the range of dose selected. In conclusion, when using a proper dose, the gamma irradiation of colonized activated carbon drastically reduced the heterotrophic activity on activated carbon without significantly impacting its adsorptive behaviour.

Microwave heating was used in the regeneration of methylene blue-loaded activated carbons produced from fibers (PFAC), empty fruit bunches (EFBAC) and shell (PSAC) of oil palm. The dye-loaded carbons were treated in a modified conventional microwave oven operated at 2450 MHz and irradiation time of 2, 3 and 5 min. The virgin properties of the origin and regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue (MB). Microwave irradiation preserved the pore structure, original active sites and adsorption capacity of the regenerated activated carbons. The carbon yield and the monolayer adsorption capacities for MB were maintained at 68.35-82.84% and 154.65-195.22 mg/g, even after five adsorption-regeneration cycles. The findings revealed the potential of microwave heating for regeneration of spent activated carbons., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

This work explores the feasibility of orange peel, a citrus processing biomass as an alternative precursor for preparation of activated carbon (OPAC) via microwave assisted K(2)CO(3) activation. The operational parameters, chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability were investigated. The virgin characteristics of OPAC were examined by pore structural analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurement. The optimum conditions resulted in OPAC with a monolayer adsorption capacity of 382.75 mg/g for methylene blue and carbon yield of 80.99%. The BET surface area, Langmuir surface area and total pore volume were identified to be 1104.45 m(2)/g, 1661.04 m(2)/g and 0.615 m(3)/g, respectively. Equilibrium data were simulated using the Langmuir, Freundlich, Dubinin-Radushkevich, Redlich-Peterson, and Toth isotherms, and kinetic data were fitted to the pseudo-first-order, pseudo-second-order and Elovich kinetic models., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The present study attempts to utilize coconut shell to prepare activated carbon using agents such as steam, CO(2) and a mixture of steam-CO(2) with microwave heating. Experimental results show that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area in excess of 2000 m(2)/g. The activation time using microwave heating is very much shorter, while the yield of the activated carbon compares well with the conventional heating methods. The activated carbon prepared using CO(2) activation has the largest BET surface area, however the activation time is approximately 2.5 times higher than the activation using steam or mixture of steam-CO(2). The chemical structure of activated carbons examined using Fourier transformed infra-red spectra (FTIR) did not show any variation in the surface functional groups of the activated carbon prepared using different activation agents., ((c) 2010 Elsevier Ltd. All rights reserved.)

Granular activated carbon (GAC) was modified by microwave irradiation and electrical heating. The characters and toluene adsorption capacity of modified GAC were studied. The results showed that for microwave heating, with the temperature increasing, the activated carbon's ability of toluene adsorption and content of the surface basic functional group were increased, specific surface area was decreased. After heated at 850 degrees C, GAC had the highest ability for toluene adsorption, at 650 degrees C and 450 degrees C, the ability for toluene adsorption of GAC were similar. For the electrical heating, the same results were obtained. But the GAC modified with electrical heating had lower capacity of toluene adsorption than microwave modified GAC. The SEM photos showed that thermal modification made the porous structure of modified GAC smoother than original GAC, but the structure of GAC shrink at high temperature. Finally, all the experimental data and SEM photos were analyzed; it indicated that due to the difference of heating mechanism and heat transmission direction, the modified GAC have different characters.

This work presents a technique for determining the radon (222Rn) diffusion length in porous materials. A mathematical model that describes the process of radon diffusion in a closed chamber, divided into two sections by a porous building material, is proposed. The derived relations allow evaluating the radon diffusion length in the material from measurements of the radon concentrations in the two sections. Preliminary experimental results are presented for the diffusion lengths of concrete and gypsum obtained by measuring the radon concentration via two standard passive detection methods: electrostatic electret chambers and activated charcoal canisters. The electret measurements were checked by a solid state continuous radon monitor.