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Retention and degradation of co-applied atrazine and fipronil was studied in laboratory constructed bio-augmented biobeds containing rice straw-compost (BM) and compost replaced with 10% rice husk ash [RHABM(10%)] or 1% wheat straw biochar [WBCBM(1%)] biomixtures. Atrazine (5000 µg, 50% WP) and fipronil (5000 µg, 0.3 G) were co-applied in 100 mL water. After 30 days, 7.31, 4.65, and 11.21 µg g−1 atrazine and 21.59, 7.41, and 37.20 µg g−1 fipronil remained undegraded in the top 3–4 cm of BM, RHABM(10%), WBCBM(1%) biobeds, respectively, suggesting that degradation of both pesticides significantly varied (p < 0.05) among the three biobeds. After 60 days 94.5%–98.3% of initially applied atrazine and 80.3%–86.9% fipronil degradation was observed. Hydroxyatrazine and sulphone were detected as the metabolites of atrazine and fipronil, respectively. Out of 5000 µg of initially applied pesticides, BM, RHABM(10%), and WBCBM(1%) biobeds accounted for 95.2%, 93.1%, and 95.2% of atrazine + hydroxyatrazine and 62.8%, 67.0%, and 71.5% of fipronil + sulphone degradation, respectively. Maximum amounts of recovered atrazine (68.8%–81.1%) and fipronil (89.8%–94.6%) were retained in the 0–5 cm sections of the biobeds. No significant effect of co-applied atrazine + fipronil was evident on the microbial parameters. This study suggested that RHA/WBC-mixed rice straw-compost biomixtures can be exploited for the detoxification of these pesticides in bio-purification systems. [ABSTRACT FROM AUTHOR]

Biochars have received much attention as efficient adsorbents for water pollutants. Besides, the chemical treatment of biochars performed to increase the adsorption capacity usually causes secondary chemical pollution and increases the cost of the process. The biomass feedstock utilised in biochar preparation impacts significantly the surface properties and adsorption capacity. Thus, the need to prepare new biochars from new feedstock with potentially high uptake capacities. Herein, we prepared new biochar (POBC) from Platanus occidentalis waste leaves (POL), which was utilised for the ultrasonic-aided adsorption of bromophenol blue (BRB) and thiazolyl blue tetrazolium bromide (TTB). The FTIR, SEM, EDX, TGA, BET, pHpzc, and elemental characterisations of POBC revealed potent surface characteristics desirable for efficient dye adsorption. An increase in the surface area from 14.31 m2/g to 31.94 m2/g and the pore volume from 0.0214 cm3/g to 0.0326 cm3/g was obtained after the conversion of the POL to POBC. Besides, the SEM images of POBC revealed a highly porous surface structure of the adsorbent. The Freundlich and pseudo-second-order model presented the best fit to the isotherm and kinetics based on the high coefficient of determination (R2 > 0.9) and low sum square errors (SSE < 0.31). The heterogeneous surface nature of POBC was inferred from the independent-oriented site model. The monolayer adsorption capacity of 45.03 mg/g and 48.8 mg/g were obtained for BRB and TTB, respectively. Thermodynamics showed an endothermic, feasible, and random uptake, and POBC displayed efficient potentials to be reused. The obtained results revealed that novel POBC is an efficient low-cost biochar with high adsorption capacity for dyes. [ABSTRACT FROM AUTHOR]

In a bid to develop efficient biochars, we prepared new biochar by the pyrolysis of Ipomoea batatas feedstock for the ultrasonic-aided adsorption of eriochrome black T (EBT) and celestine blue (CB) dyes. The characterisation of the Ipomoea batatas-derived biochar (IBBC) showed potent functional groups, good thermal stability, porous structure and a point of zero charge of 6.41. The pH of 2.0 and 7.0 was found to be optimum for the uptake of anionic EBT and cationic CB onto IBBC, respectively. A decrease in the surface area of IBBC from 96.35 m2/g to 48.43 m2/g and 32.11 m2/g was obtained after the adsorption of EBT and CB, respectively. Thermogravimetric analysis revealed high thermal stability of IBBC up to 350°C. The Energy dispersive X-ray (EDX) spectrum revealed carbon (52.6%), oxygen (24.5%) and potassium (7.1%) as the major component of the biochar. The elemental analysis showed carbon, hydrogen and nitrogen compositions of 55.4%. 2.6% and 1.2%, respectively. Moreover, a biochar yield of 36.2% was obtained. The adsorption of both dye molecules was well correlated by the Freundlich isotherm, supported by the Scatchard model analysis. Kinetics was well fitted to the film diffusion and pseudo-second-order models, while thermodynamics showed an endothermic and spontaneous dye uptake on IBBC. The adsorption capacity of the biochar for EBT and CB was 59.24 mg/g and 63.69 mg/g respectively. Percentage desorption of 87.5% for EBT and 82.3% for CB was achieved during regeneration of the dye-loaded biochar. Moreover, IBBC showed good potentials to be reused for adsorption. The results revealed the potentials of the novel biochar for efficient adsorption of both cationic and anionic dye species. [ABSTRACT FROM AUTHOR]

In recent years, numerous research studies have been performed in the field of pyrolysis and thermochemical biomass transformation into biofuels, i.e. bio oil, biochar and biogas. Additionally, pyrolysis is an efficient and effective conversion technology as compared to other thermochemical technologies due to various socioeconomic benefits. Biomass, and its composition, plays an ultimate role in the determination of pyrolysis products and is an ecofriendly or promising alternative source of renewable energy. This review paper attempts to suggest specific criteria for biomass selection for the pyrolysis process to obtain maximum yield of biooil, biochar and biogas. Lignin, cellulose and hemicellulose are the key constituents present in varying biomass which greatly affect the products of pyrolysis. This review paper summarises biomass resources, types, the composition of biomass, preliminary tests and physical and chemical characteristics for suitable selection of biomass for pyrolysis. [ABSTRACT FROM AUTHOR]

Adsorption capacity of activated biochar derived from Eichhornia crassipes was investigated for the sequestration of Cr (VI) from aqueous solution. Biochar was prepared and activated with different agents viz., 85% phosphoric acid, 0.5% sulphuric acid, 1 M ferric chloride and 10% polyethylenimine. Adsorption parameters were optimised by using Box–Behnken model of Response Surface Methodology (RSM), where the P value lesser than 0.05 and higher F value explained the significance of the model. Concentration and time showed positive effect while pH, biosorbent dosage and biosorbent size represented negative effect on adsorption. The optimum conditions for adsorption of Cr (VI) by activated biochar obtained from the model were pH: 2, biosorbent dosage was 1%, biosorbent size 1 mm, solute concentration of 985 mg/L and equilibrium time of 35 hours. An increase in concentration of solute molecules increased the adsorption of Cr (VI), whereas percent removal was reduced. Equilibrium relationship between sorbent and sorbate was determined using the isotherms Langmuir, Freundlich and Temkin models. Isotherm study was supported by Langmuir where sorption occurs on monolayer. The rate of adsorption and its mechanisms elucidated through kinetic studies. The higher correlation coefficient of 0.9985 reveals the significance of the studied models. Kinetics study fits well with the pseudo-second-order kinetics whereas isotherm study was best described by Langmuir model with maximum adsorption capacity of 50.0 mg g−1 under biochar activated with phosphoric acid (PA-WBC). Among the activation methods PA-WBC showed maximum chromium adsorption due to the influence of H+ ions present on the surfaces which highly favoured the sorption of anions. Hence, this activated biochar can be effectively utilised for the removal of Cr (VI) from industrial waste water, it was further suggested that water hyacinth has the additional advantage that it reduces or even eliminates the diverse impact of the weed on the environment. [ABSTRACT FROM AUTHOR]

The pollution of soils and groundwater by heavy metal pollutants is a widespread environmental problem, particularly in Iran. One cost-effective method to remediate the polluted soils is phytoremediation, in which different plants are used to extract the heavy metals from soil and accumulate them in their organs. In this study, the phytoremediation potential of native plants of Southwestern Iran in removing nickel and lead from polluted soil was assessed separately and in combination with organic amendments of compost and biochar.Hence, the pot experiments were conducted in the greenhouse using soil gathered from the Pazanan oil refineryin Gachsaran, located at Kohgiluyeh and Boyer-Ahmad Province. Then, the hierarchical cluster analysis was applied to classify the different treatments of amendments.The results indicated that the phytoremediation strength of three native species for Ni uptake was C. procera> St. Plumosa > M. sativa; and for Pb uptake was St. Plumosa > C. procera> M. sativa. Also, the utilisation of organic materials originated from urban waste caused to increase in the Ni and Pb accumulation in root and shoot of these species as well as the residual concentration of the metals in soil. Based on the cluster analysis, the treatment of biochar 2% showed the most effect on the residual concentration of heavy metals in soil (1128.00 mgkg−1);the treatment of biochar 1% represented the highest accumulation of metals at the root (158.82 mgkg−1), while all treatments of different amounts of amendments have the same effect on the accumulation of heavy metals in the shoot (151.38 mgkg−1). In general, cluster analysis showed that the organic amendments, especially biochar even at low amounts can improve the phytoremediation capability of the studied native species in removing Ni and Pb from polluted soil. [ABSTRACT FROM AUTHOR]

The thermally modified Parthenium biochar was used as an efficient adsorbent for removal of Cd from water. Parthenium biochar (PBC) prepared at 500°C was thermally activated by re-heating it at 700°C. PBC and thermally modified biochar (TMPBC) was characterised by FTIR, SEM-EDS, BET-surface area and XRD. The surface area of TMPBC (3.44 m2g−1) was higher than PBC (1.89 m2g−1). The optimum conditions for Cd adsorption was found to be pH, 5.0; biochar dose, 2.5 (g L−1); time, 30 min; temperature 25°C; initial Cd concentration, 100 mg L−1. Cadmium removal parameters were assessed using kinetic (pseudo first and second order) and adsorption models (Langmuir, Freundlich, and Redlich-Peterson). Cd removal followed pseudo second order kinetic model. The Cd removal capacity of TMPBC (129.2 mg g−1) was significantly higher than PBC (59.3 mg g−1). Cd removal by TMPBC (97–99%) was also demonstrated for a surface and underground waters. FTIR, XRD and SEM-EDS analysis confirmed the ion exchange and otavite precipitation mechanisms of Cd removal by biochar. The thermal modification technique could be an alternative for commercially available activated carbons; however this needs to be explored with different biomasses and other elements. [ABSTRACT FROM AUTHOR]

Different modified biochars were prepared by impregnating with different metal oxide nanoparticles including AgO, CuO and ZnO onto leaf of lotus tree. The prepared nanocomposites were characterised using X-ray diffraction (XRD) and field emission-scanning electron microscopy (FESEM). The results revealed that the metal oxide affected morphology of the biochars. Graphene sheets were evident especially in the case of Zn-modified biochar. Particle size of biochar, Ag-biochar, Cu-biochar and Zn-biochar revealed to be in the range of 33.5–214.5 nm, 105.3–231.9 nm, 33.5–142.9 nm and 37.2–66.9 nm, respectively. Textural properties of the biochars were determined by using Brunauer–Emmett–Teller (BET) and BJH models based on N2-adsorption-desorption isotherms. Box-Behnken design (BBD) was used to optimise the different effective parameters and to compare the efficiency of the different biochars towards the removal of Cr and Co ions. Isotherms of the biochars were also studied. The adsorption isotherms were fitted to Langmuir and Freundlich models. The biochars obeyed Langmuir adsorption model and their maximum adsorption capacities were 107.5 mg/g for Co2+ ion and 113.6 mg/g for Cr3+. The modified biochar was capable of removing Cr3+ and Co2+ ions up to 78% and 98%, respectively. The modified biochar has also shown excellent photocatalytic performance for the degradation of chromate ion. 81.6% of chromate ion degradation has been achieved with the incorporation of Zn-biochar under sunlight irradiation. Adsorption characteristics of the modified lotus leaf biochar were compared with the previously reported biochars. The results confirmed the superiority of the proposed biochar. [ABSTRACT FROM AUTHOR]

In recent years, there are many concerns about the potential risks of contamination of emerging compounds in water resources and their adverse effects on human health and the environment. Today, the production and use of drug compounds for the treatment of human and animal diseases is increasing. The aim of this study was to investigate the effect of the biosorbent prepared from pine bark on the removal of tetracycline from aqueous solutions. In this study, the effect of various variables including pH (2–12), adsorbent dose (1–2 g)), tetracycline concentration (50–500 mg/L), contact time (10–120 min)) and temperature (10–50°C) as well as the structural properties of biochar were examined. The isotherms, kinetics and thermodynamics of the adsorption process were also evaluated. The residual concentration of tetracycline after adsorption by DR5000 spectrophotometer of the Hack Company at 292 wavelengths was read. Using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods, it was found that the biochar structure has many pores for adsorption and also has functional groups including hydroxyl, carbonyl and amine, which increases the adsorption capacity. Maximum removal of tetracycline (89.5%) was achieved in 15 minutes, pH 5.1 and dose 1 g. In this study, the removal efficiency of tetracycline increased with increasing temperature and adsorbent dose and decreased with increasing contaminant concentration. The adsorption isotherm of tetracycline at maximum adsorption capacity (58.47 mg/g) is consistent with the Langmuir model and the adsorption kinetics follows the pseudo- second order model. According to the results of this study, it was found that biochar produced from pine bark is a cheap and efficient adsorbent in the removal of tetracycline antibiotic and can be used to remove this antibiotic in hospital wastewaters. [ABSTRACT FROM AUTHOR]

Chrome tanning in India leads to severe contamination of soil and water. Due to the indiscriminate disposal of effluent from tanneries, several thousand hectares of agricultural lands have been degraded over several decades in Tamil Nadu. Several researchers were involved in developing remediation technologies for chromium contamination.Adsorption and desorption of Cr on soil determine the mobility of Cr and its environmental impact. There are several studies regarding the adsorption/desorption of Cr. A strategic study regarding the mechanism of adsorption/desorption of Cr to the context of remediation technologies is essential. A better understanding of the adsorption and desorption mechanism of Cr aids in developing a suitable remediation strategy. Therefore, in the present investigation, the adsorption Cr on soil and some critical factors affecting the adsorption were studied. The Cr adsorption on soil recorded maximum and was best illustrated by the Freundlich isotherm (R2 = 0.994) than the Langmuir isotherm (R2 = 0.841). Amongst the bio-amendments, biochar was found to enhance the adsorption of Cr on the soil. The co-contaminants such as cadmium and lead significantly reduced the adsorption of Cr. Further, a desorption study was carried out with different desorption agents such as NaOH, CH3COONH4and EDTA. It was found that NaOH exhibited higher desorption efficiency than the other agents. The results reveal that adsorption and desorption mechanisms aids in predicting the toxicity of Cr. This study also shows that the soil pH, bio-amendments, and co-contaminants in the contaminated soil may play a significant role in the remediation process. [ABSTRACT FROM AUTHOR]

Effluent water from dyeing industries is a challenging issue. The purpose of this study was to investigate the adsorption properties of locally available Chinar tree (Platanus orientalis) lingo cellulosic materials as adsorbents for the removal of crystal violet dye from aqueous solution. The study shows that the Chinar leaf powder and Chinar leaf biochar can be used as a potential plant by-product adsorbent for the removal of crystal violet from aqueous solution. The adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and carbon hydrogen and nitrogen analyzer (CHNS). In batch optimization studies, the maximum removal efficiency for the adsorbents was obtained at the optimum levels of contact time (30 min), adsorbent dose (2.5 g L−1), initial dye concentration 20 mgL−1 and pH 6.52. The equilibrium adsorption data were found to follow both Langmuir and Freundlich models and maximum monolayer capacity of Chinar leaf powder and its biochar were found to be 25.88 and 30.01 mg.g−1. Also the Langmuir and Freundlich isotherm model constants RL(0.0425 and 0.00686 for Chinar leaf powder and Chinar leaf biochar, respectively) and n (1.3106 and 1.6103 for Chinar leaf powder and Chinar leaf biochar, respectively) suggesting favorable adsorption of crystal violet on the adsorbents. Kinetic analysis for both adsorbents revealed that adsorption experimental data was best fitted by pseudo-second-order model(R2 = 0.999). Gibb's free energy is −2.14473 to −4.23219 for Chinar leaf powder and −7.18828 to −11.1027 for Chinar leaf biochar showing the process is spontaneous. The enthalpy changes of Chinar leaf powder and its biochar are negative (−20.6611) and positive (22.72549) indicating exothermic and endothermic processes, respectively. Uptake efficiency (>90%) recorded at an equilibrium time of 30 min shows that Chinar leaf powder and biochar were fast and effective adsorbents for the removal of crystal violet. [ABSTRACT FROM AUTHOR]

Pyrolysis of Prunus dulcis was performed in the presence off our catalysts (ZnCl2, Fe2O3, Alumina, and ZSM-5) using a fixed bed tubular reactor. The factors affecting the product yield were premeditated. Prunus dulcisshowed a high heating value of 19.72 MJ/Kg which makes it very efficient for biofuel usage. Biochar obtained showed high carbon content and large heating values. Different pyrolytic product yields were obtained with different catalysts. Among all the catalysts, alumina and ZSM-5 showed a maximum yield of liquid product. FT-IR, GC-MS, and elemental analysis were performed to determine the product yield and bio oil compositions. [ABSTRACT FROM AUTHOR]

The rice husk biochar (RHB), Ca-alginate (CA), and biochar/ca-alginate composites (CA-RHB) was synthesised for the removal of aqueous Cu(II) and Zn(II) and characterised by BET, SEM, EDS, and FT-IR analysis. The adsorption experiments of Cu(II) and Zn(II) ions by RHB, CA, and CA-RHB were studied on effects of initial concentration, pH, and contact time. The purpose of characterisation the adsorption behaviours of Cu(II) and Zn(II) ions on RHB, CA, CA-RHB1, CA-RHB2, CA-RHB3, and CA-RHB4, the Langmuir, Freundlich, Temkin, Redlich-Peterson, Hill and Unilan isotherm models and the pseudo-first-order, the pseudo-second order, Intra-particle diffusion model, Elovich and Avrami kinetic models apply to the experimental adsorption data. The maximum Cu (II) adsorption capacity estimated with Langmuir isotherm modelling was 44.60 mg g−1, for CA, 41.74 mg g−1 for CA-RHB1, 42.62 mg g−1 for CA-RHB2, 35.45 mg g−1 for CA-RHB3, and 31.52 mg g−1 for CA-RHB4, and 10.56 mg g−1 for BMB. The maximum Zn (II) adsorption capacity estimated with Langmuir isotherm modelling was 43.32 mg g−1, for RHB, 25.07 mg g−1 for CA, 22.23 mg g−1 for CA-RHB1, 23.68 mg g−1 for CA-RHB2, 22.03 mg g−1 for CA-RHB3, and 34.41 mg g−1 for CA-RHB4, [ABSTRACT FROM AUTHOR]

Composition of the biomixture is crucial for the success of a bio-purification system. The rice straw-compost biomixture (BM) was mixed with the rice husk ash (RHA, 5 and 10%), sugarcane bagasse ash (SBA, 5 and 10%) and wheat straw biochar (WBC, 1, 5 and 10%) and adsorption of atrazine and fipronil was studied. Fipronil was more sorbed than atrazine in all biomixtures. Both ashes and biochar increased sorption of atrazine, but the effect varied with the level of the amendment. The adsorption coefficient (Kd) values for atrazine in biomixtures were 6.82 (BM), 8.64 (RHA5%), 8.80 (RHA10%), 7.26 (SBA5%), 7.66 (SBA10%), 8.26 (WBC1%), 26.79 (WBC5%) and 46.68 (WBC10%). Ashes did not have much effect of fipronil sorption [48.92 (BM), 49.68 (RHA5%), 54.04 (RHA10%), 45.35 (SBA5%), 46.11 (SBA10%)]; however, WBC1% biomixture showed 100% fipronil sorption. The adsorption data were subjected to the Freundlich, the Langmuir and the Temkin isotherms. Among the three isotherms used for adsorption data modelling, the Freundlich isotherm best explained the pesticide sorption. This study suggested that ashes/biochar mixed rice straw-compost biomixtures can be exploited in bio-purification systems. [ABSTRACT FROM AUTHOR]

Pharmaceutical and personal care products have received increasing more attention worldwide. Diclofenac was found to be one of the most detected pharmaceuticals in environmental matrixes and has acute toxicity against micro-living organisms. The present study aimed to investigate the application of magnetic gelatin modified peanut shell biochar (PBG) as an environmentally friendly adsorbent for the removal of sodium diclofenac (DCF) in the aqueous phase. Through SEM, EDS, BET, XRD, XPS, and FTIR characterisation techniques, the surface morphology, element components, specific surface area as surface functional groups of PBG were different from the pristine biochar. Batch adsorption experiment showed that PBG performed very high DCF adsorption capacity (qmax = 348.9 mg/g at pH = 6.5, T = 298 K). The adsorption capacity was significantly affected by pH solution with a decrease trend when pH >6. The experimental results could be satisfactorily fitted by Pseudo-second order kinetic model, and Temkin isotherm model. Thermodynamic study indicated that the adsorption process was non-spontaneous and endothermic. Some external agents such as humic acid and common ions exhibited a negative effect on the removal of DCF in the co-solute system. The adsorption capacity of the PBG adsorbent remained at 71.5% even after five cycles of regeneration, which demonstrated the stability and reusability for further removal of DCF. Besides, the proposed adsorption mechanism might contain electrostatic interactions, hydrogen bonds interactions, and π-π interactions. Considering the simple fabrication approach and the excellent adsorption performance, the PBG adsorbent can be evaluated as a potential material for environmental remediation applications. [ABSTRACT FROM AUTHOR]

Using rice straw as a carbon source, photoluminescent carbon nanodots (CNDs) were quickly prepared by pyrolysis under insufficient air flow and ultrasonic methods without the addition of other chemical reagents. This method is simple and environmentally friendly. The prepared CNDs have quasispherical nanoparticles with the average diameter of 5.8 nm observed from TEM image, and have good fluorescence performance with the quantum yield of 5.1%. The CNDs possess a clear correlation between photoluminescence wavelength and intensity and excitation wavelength, as well as good water solubility and salt resistance. In addition, the luminescent CNDs can not only be effectively taken up by HeLa cells and HUVECs but also exhibit low cytotoxicity and good biocompatibility from CCK8 test and laser confocal imaging observations, respectively, making them promising complement to future cellular imaging assay applications. Moreover, the prepared CNDs can be used as ion sensors to selectively and sensitively detect Fe3+ ions in the concentration range of 0–1000 μM with a detection limit of 300 nM. Our proposed strategy for preparing carbon nanodots explores a new way to obtain fluorescent carbon materials and avoid environmental pollution caused by burning straw. [ABSTRACT FROM AUTHOR]

The aim of the current research is to eliminate the Cu(II) ions from aqueous solution using biochar, namely sulphuric acid-modified Annona reticulata seeds (SMARS). The removal process followed the Freundlich and pseudo-first-order models. At optimum conditions, Langmuir adsorption capacity of the SMARS for Cu(II) ions was calculated as 561.1 mg/g. The results of this work indicate that the adsorption was feasible, spontaneous and exothermic, which was controlled by film diffusion. An adsorber has been designed based on Freundlich model. Desorption results indicate that 0.2 N of the hydrochloric acid solution provides the maximum elimination of heavy metals from the Cu(II) ions loaded adsorbent. The column influencing parameters like Cu(II) ions concentration, bed height and flow rate have been experimented. The best operating condition for removal of Cu(II) ions by SMARS in column mode of operation has been recorded as flow rate = 5 mL/min, bed height = 8 cm, adsorbent amount = 16 g, solution pH = 6.0 and at the temperature = 30°C. The column experimental data have been characterised by applying Bed Depth Service Time and Thomas models. The results indicate that the SMARS has exceptional adsorption behaviour in the elimination of heavy metals from the aqueous solution. [ABSTRACT FROM AUTHOR]

Biochars obtained by biomass pyrolysis have been proposed as a soil amendment to improve soil properties and fertility as well as to retain pesticides and other environmental contaminants. The present study investigates the degradation of metribuzin herbicide and its metabolites deamino- (DA), deaminodiketo- (DADK) and diketo- (DK) metribuzin under simulated solar light and dark conditions as well as their mobility using TLC plates coated with soil and soil‒biochar mixtures at 1% and 5% w/w ratio. Biochar was characterised by X-Ray diffraction, porosimetry, scanning electron microscopy and Fourier transform infrared spectroscopy. Degradation under light conditions followed biphasic kinetics, with bi-exponential model fitted better for the soil substrate, while the Gustafson–Holden model was found more appropriate to describe degradation kinetics in 1% soil/biochar mixture. In soil, DA presented the lowest degradation rate (DT50:440.9 h), followed by metribuzin (DT50:208.0 h), DADK (DT50:110.8 h) and DK (DT50:106.5 h). The addition of biochar reduced drastically the degradation or even inhibited the photolytic process for the studied reaction period. The mobility retention factor (Rf) in soil ranged from 0.49 for metribuzin to 0.63 for DADK. The addition of biochar practically immobilises the compounds in the surface layer as Rf ranged from 0.14 to 0.10 for metribuzin and from 0.23 to 0.16 for DADK in soil/biochar mixtures 1% and 5%, respectively. In conclusion, the addition of biochar reduced dramatically the photodegradation rates as well as the mobility of metribuzin and its metabolites due to increased adsorption. [ABSTRACT FROM AUTHOR]

A rapid, effective and sensitive method to quantitatively determine six fungicide residue was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). The target compounds were extracted by using acetonitrile and the sorbent used for clean-up in this modified QuEChERS analytical method were biochar, multiwalled carbon nanotubes (MWCNT) and graphitized carbon black (GCB). Results indicated that the MWCNT (10 mg) was the most effective sorbent in removing pigment. This method was validated on spinach, tomato, cucumber, celery, lettuce, rape, pakchoi, romaine lettuce and eggplant matrices spiked at three concentration levels of 0.01, 0.1 and 1 mg kg−1. It exhibited recoveries between 73.1% and 118.2% with RSD values below 20%. Matrix-matched calibrations were performed with the coefficients of determination >0.9901 between concentration levels of 0.01–1 mg kg−1. The limit of quantity (LOQ) for six pesticides ranged from 0.0036 to 0.011 mg kg−1. The developed method was satisfactorily applied to determine pesticide residues in market vegetable samples. [ABSTRACT FROM AUTHOR]