A Box-Behnken design for determining the optimum experimental condition of the fungicide (Vapam) sorption onto soil modified with perlite

In the present study, response surface methodology (RSM) based on the Box-Behnken design (BBD) was employed to investigate the effects of the different operating conditions on the removal of the fungicide (Vapam) onto soil modified with perlite using sorption process. The process parameters such as pH of the fungicide solution (2, 5 and 8), temperature (15, 25 and 35°C), shaking time (2, 13 and 24 h) and the percentage of perlite in the modified soil (0, 2 and 4 %) were investigated using a four-factor-three-level Box-Behnken design at an initial fungicide concentration of C₀ = 1.6 mg/L as a fixed input parameter. A second-order quadratic model suggested the optimum conditions to be as follows: fungicide solution pH of 3.57, temperature of 15°C, shaking time of 3.5 h and 4% of perlite in the modified soil which resulted in the improvement of Vapam sorption. Under optimum conditions, the fungicide (Vapam) removal was predicted 12.88 μg/g by BBD. The confirmatory experiments were conducted and the results revealed that the fungicide removal was 13.14 μg/g which indicated that the predicted and the observed values of response (Vapam removal) were in close agreement. Therefore, the soil modified with perlite holds good potential for Vapam sorption. This is the first report on fungicide Vapam sorption onto soil modified with perlite using statistical experimental design employing response surface methodology.     

Parameter optimization of the fungicide (Vapam) sorption onto soil modified with clinoptilolite by Taguchi method

This study employs the Taguchi optimization methodology to optimize the effective parameters for the pesticide (Vapam) sorption onto soil modified with natural zeolite (clinoptilolite). The experimental factors and their ranges chosen for determination of the effective parameters were: initial Vapam concentration (0.4-1.6 mg/L), initial pH of the pesticide solution (2-12), the percentage of clinoptilolite in the modified soil (0-6 %), temperature (15-35°C) and shaking time (2-24 h). The orthogonal array (OA) L(16) and the bigger the better response category of the Taguchi method were selected to determine the optimum conditions: initial Vapam concentration (1.2 mg/L), initial pH of the pesticide solution (2), the percentage of clinoptilolite in the modified soil (4 %), temperature (15°C) and shaking time (2 h). The results showed that in comparison with other parameters, the initial Vapam concentration was the most effective one for the sorption of this pesticide onto soil, modified with clinoptilolite. Moreover, after determining the optimum levels of the sorption process parameters, confirmation experiments were performed to prove the effectiveness of the Taguchi's experimental design methodology.     

Parameter optimization of the fungicide (Vapam) sorption onto soil modified with clinoptilolite by Taguchi method

This study employs the Taguchi optimization methodology to optimize the effective parameters for the pesticide (Vapam) sorption onto soil modified with natural zeolite (clinoptilolite). The experimental factors and their ranges chosen for determination of the effective parameters were: initial Vapam concentration (0.4–1.6 mg/L), initial pH of the pesticide solution (2–12), the percentage of clinoptilolite in the modified soil (0–6 %), temperature (15–35°C) and shaking time (2–24 h). The orthogonal array (OA) L₁₆ and the bigger the better response category of the Taguchi method were selected to determine the optimum conditions: initial Vapam concentration (1.2 mg/L), initial pH of the pesticide solution (2), the percentage of clinoptilolite in the modified soil (4 %), temperature (15°C) and shaking time (2 h). The results showed that in comparison with other parameters, the initial Vapam concentration was the most effective one for the sorption of this pesticide onto soil, modified with clinoptilolite. Moreover, after determining the optimum levels of the sorption process parameters, confirmation experiments were performed to prove the effectiveness of the Taguchi's experimental design methodology.     

响应面法优化UV／H2O2光氧化法处理高浓度LAS废水

采用响应面法对UV／H2O2光氧化法处理高浓度LAS废水的工艺参数进行了系统研究。根据Box—BehnkenDesign（BBD）设计原理，以初始pH与H2O2投加量、反应时间和温度为主要影响因素，设计4因素3水平共29个实验点的实验方案，并建立了二次响应面拟合模型。方差分析表明，初始pH与H2O2投加量、反应时间和温度以及初始pH和H2O2投加量、H2O2投加量和温度之间的交互作用，对实验结果具有显著性影响。实验得到的光氧化高浓度LAS废水最佳工艺条件，pH为4．0，H2O2投加量为40mmol／L，反应时间为90min，温度为25℃，在此条件下，LAS的平均去除率为98．1％。     

Adsorption and desorption variability of four herbicides used in paddy rice production

This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption-desorption processes. Four soils from Melozal (35° 43' S; 71° 41' W), Parral (36° 08' S; 71° 52' W), San Carlos (36° 24' S; 71° 57' W), and Panimavida (35° 44' S; 71° 24' W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g?1) and were related to soil pH. Molinate showed K(d) values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g?1 and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K(d) values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g?1. MCPA K(d) ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g?1, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.     

Application of response surface methodology to the removal of the antibiotic tetracycline by electrochemical process using carbon-felt cathode and DSA (Ti/RuO2-IrO2) anode

The removal of antibiotic tetracycline (TC) from water by electrochemical advanced oxidation process (EAOP) was performed using a carbon-felt cathode and a DSA (Ti/RuO(2)-IrO(2)) anode. The influence of applied current, initial pH and initial TC concentration on TC removal efficiency was investigated. Response surface methodology (RSM) based on Box-Behnken statistical experiment design (BBD) was applied to analyze the experimental variables. The positive and negative effects of variables and the interaction between variables on TC removal efficiency were determined. The applied current showed positive effect, while the initial pH value and initial tetracycline concentration gave negative effect on TC removal. The interaction between applied current and initial pH value was significant, while the interactions of initial TC concentration with applied current or initial pH were not pronounced. The results of adequacy check confirmed that the proposed models were accurate and reliable to analyze the variables of EAOP. The reaction intermediates were identified by high-performance liquid chromatography-mass spectrometry (LC-MS) technique and a plausible degradation pathway for tetracycline degradation was proposed. The acute toxicity experiments illustrated that the Daphnia magna immobilization rate reached the maximum after 240 min of electrolysis and then decreased with the progress of the reaction.     

Predictability by Box-Behnken model for carbaryl adsorption by soils of Indian origin

This study was undertaken to investigate the adsorption capacity of carbaryl on four Indian soils with different physiochemical properties. A batch adsorption study was carried out in order to evaluate the maximum adsorption capacity of carbaryl using a Response Surface Methodology (RSM). The effects of operating parameter such as initial carbaryl concentration (1–20 mgL^?1), adsorbent dosage (0.5–6 g) and contact time (10–180 min) were examined. The proposed quadratic model for Box-Behnken design fits very well to the experimental data because it may be used to navigate design space according to ANOVA results. The regression co-efficient (R²) of the models developed and the results of validation experiments conducted at optimal conditions strongly suggests that the predicted values are in good agreement with experimental results. Contour and response surface plots are used to determine the interactions effects of main factors and optimal conditions of the process. The experiment can be utilized as a guideline for better understanding of carbaryl adsorption onto soil under different operating conditions. The results show that the forest soil is most efficient in binding carbaryl (Sevin) than the other types of soil tested.     

Optimization of preparation process of activated carbon from chestnut burs assisted by microwave and pore structural characterization analysis

In this study, activated carbon was prepared from Chinese chestnut burs assisted by microwave irradiation with potassium hydroxide (KOH) as activator, and the process conditions were optimized employing Box-Behnken design (BBD) and response surface methodology (RSM). The optimized variables were irradiation time, impregnation time, and mass ratio of alkali-to-carbon, and the iodine adsorption value was used to evaluate the adsorption property of activated carbon. The optimal preparation conditions were determined as follows: irradiation time 17 min, impregnation time 240 min, and mass ratio of alkali-to-char 1.5:1. Meanwhile, the relatively high iodine adsorption value (1141.4 mg/g) was also obtained. Furthermore, the pore structural characterization of activated carbon was analyzed. The analyzed results showed a larger Brunauer-Emmett-Teller (BET) specific surface area (1254.5 m²/g) and a higher microporosity ratio (87.2%), a bigger total pore volume (0.6565 m³/g), but a smaller average pore size (2.093 nm), which demonstrated the obtained activated carbon possessed strong adsorption capacity and well-developed microporous structure. This research could not only establish the foundation of utilizing chestnut burs to prepare activated carbon, but also provide the basis for exploitation of Chinese chestnut by-products.

Implications: Because Chinese chestnut burs are the by-products and usually discarded upon harvesting subsequently, the utilization of chestnut burs as a potential source of activated carbon is of great profit to the chestnut processing industries.     

Cyprodinil retention on mixtures of soil and solid wastes from wineries. Effects of waste dose and ageing

In spite of its wide-world economic relevance, wine production generates a huge amount of waste that threatens the environment. A batch experiment was designed to assess the effect of the amendment of an agricultural soil with two winery wastes (perlite and bentonite wastes) in the immobilization of cyprodinil. Waste addition (0, 10, 20, 40, and 80 Mg ha^?1) and different times of incubation of soil-waste mixtures (1, 30, and 120 days) were tested. The addition of wastes improved the soil’s ability to immobilize cyprodinil, which was significantly correlated to total C content in soil-waste mixtures. Longer incubation times decreased the cyprodinil sorption possibly due to the mineralization of organic matter but also as a consequence of the high pH values reached after bentonite waste addition (up to 10.0). Cyprodinil desorption increased as the amount of waste added to soil, and the incubation time increased. The use of these winery wastes contributes to a more sustainable agriculture preventing fungicide mobilization to groundwater.     

Effects of temperature on sorption-desorption processes of imidacloprid in soils of Croatian coastal regions

Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equations, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were non-linear and may be classified as L-type, suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the K( sor ) ( F ) values decreased for all the tested soils as the temperature increased, indicating that the temperature strongly influences the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous processes. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and partitioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature-dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature treatments existed, and it was more pronounced at 20°C in the soils with higher OC content. The study results emphasize the importance of thermodynamic parameters in controlling soil pesticide mobility in different geographical locations, seasons and greenhouse conditions.     

Abiotic reductive dechlorination of chlorinated ethylenes by soil

Abiotic reductive dechlorination of chlorinated ethylenes by soil in anaerobic environments was characterized to improve knowledge of the behavior of chlorinated ethylenes in natural systems, including systems modified to promote attenuation of contaminants. Target organics in the soil suspension reached sorption equilibrium in 2 days and the sorption isotherm of target organics was properly described by the linear sorption model. A modified Langmuir-Hinshelwood model was developed to describe the kinetics of reductive dechlorination of target organics by soil. The rate constants for the reductive dechlorination of chlorinated ethylenes at the reactive surfaces of reduced soils were found in the range between 0.055 (+/- 8.9%) and 2.60 (+/- 3.2%) day(-1). The main transformation products in reduced soil suspensions were C2 hydrocarbons. No chlorinated intermediates were observed at concentrations above detection limits. Five cycles of reduction of the soil followed by oxidation of the soil with trichloroethylene (TCE) did not affect the removal of TCE. The removal was affected by the reductants used and increased in the order: Fe(II) < dithionite < Fe(II) + dithionite.     

Improvement of the hydrocarbon phytoremediation rate by Cyperus laxus Lam. inoculated with a microbial consortium in a model system

Hydrocarbon phytoremediation by Cyperus laxus Lam. growing on perlite and inoculated with hydrocarbon-degrading microorganisms was evaluated. Total petroleum hydrocarbons (TPH) were extracted from weathered soil (60.7 g of TPH kg(-1) of dry soil) and spiked on perlite at initial concentration of 5 g of TPH kg(-1) of dry perlite. Phenological characteristics, total microbial viable counts, hydrocarbon degraders and residual hydrocarbons were determined through 180 days of culture. Phenological characteristics of inoculated plants were improved as compared with non-inoculated plants: root biomass was 1.6 times greater, flowering time was reduced (13%), and the number of inflorescences was 1.5 times higher. The rhizospheric bacterial and fungi counts were higher for planted treatments (inoculated and not inoculated) than for unplanted pots. The maximum phytoremediation rate (0.51 mg of TPH g(-1) of dry plant d(-1)) for inoculated plants was reached at 60 days of culture, and was two times higher than for non-inoculated plants (55% TPH removal). Similar hydrocarbon phytoremediation extent values for inoculated (90%) and non-inoculated (85%) plants were obtained at 180 days of culture. The present study demonstrated that mutual benefits between C. laxus and inoculated hydrocarbon-degrading microorganisms are improved during phytoremediation. It is pertinent to note that this is the first report of hydrocarbon phytoremediation by Cyperus laxus Lam., a native plant growing in highly contaminated swamps.     

响应面法优化克浅十油田废水的混凝沉淀工艺

以克浅十污水处理站原水为研究对象,采用混凝沉淀工艺,探讨优选出的复配混凝剂投加量、助凝剂投加量及静置时间对原水中浊度和总铁去除效果的影响.应用Box-Behnken中心组合实验和响应面分析法,建立混凝剂对处理原水的二次多项式数学模型,确定了混凝沉淀去除原水浊度和总铁的优化工艺参数分别为:复配混凝剂投加量为152.15 mg/L、143.84 mg/L,助凝剂投加量为4.14 mg/L、4.32 mg/L,静置时间为11.77 min、11.22 min.在此工艺条件下回归方程得到的浊度和总铁的去除率预测值与实验值接近,且拟合性良好,误差介于3％～5％之间.通过均值内插法,对比浊度和总铁的多元二次回归方程,推导得出的2组最佳工艺条件均能满足浊度和总铁的去除要求.     

Influence of modified soils on the removal of diesel fuel oil from water and the growth of oil degradation micro-organism

Three soils were modified with two kinds of cationic surfactants in order to increase their sorptive capabilities for organic contaminants. Sorption of diesel fuel oil in water by these modified soils had been investigated. Modified soils can effectively sorb diesel fuel oil from water. The sorption capability of modified soils is: HDTMA-black soil > HDTMA-yellow brown soil > HDTMA-red soil > TMA-black soil > TMA-yellow brown soil > TMA-red soil. Sorption of diesel fuel oil by natural soils and HDTMA modified soils is via partition, the sorption isotherms can be expressed by Henry equation, and logK(SOM) is 2.42-2.80, logK(HDTMA) is 3.37-3.60. Sorption isotherms of TMA modified soils can be expressed by Langmuir equation, the saturation sorption capacities are 1150 (TMA-black soil), 750 (TMA-yellow-brown soil), 171 mg/kg (TMA-red soil), respectively. A diesel fuel oil degradation micro-organism (Pseudomonas sp.) was isolated in the lab. To test the influence of the modified soils on the micro-organism, various growth curves of Pseudomonas in different conditions were drawn. Pseudomonas can grow very well with natural soils and TMA modified soils. The acclimation period of Pseudomonas is reduced. As to HDTMA modified soils, HDTMA loading amount is very important. When HDTMA loading amount is no higher than 0.5 CEC, the micro-organism can grow very well after a long acclimation period.     

Evaluation of epoxiconazole bioavailability in soil to the earthworm <Emphasis Type="Italic">Aporrectodea icterica</Emphasis>

In soil, the determination of total concentration using an exhaustive extraction method has little relevance to evaluate the exposure of an organism to a chemical, because of sorption processes. This study aims to propose a mild extraction method to evaluate the bioavailability of the fungicide epoxiconazole to the earthworm Aporrectodea icterica. Experiments were conducted in soils presenting various textures and organic carbon contents, spiked with formulated epoxiconazole 7 to 56 days prior to their extraction. In parallel, the epoxiconazole concentration was determined in exposed earthworms and the fungicide’s effects were evaluated by measuring weight gain, enzymatic activities and total protein contents. Among the various mild chemical solvents tested to evaluate the environmental availability of the fungicide, the 50 mM hydroxypropyl-β-cyclodextrin solution allowed to extract around 30 % of epoxiconazole. This percentage corresponded to the ratio determined in exposed A. icterica under similar soil conditions. Furthermore, this mild method was demonstrated to be sensitive to soil sorption capacities and to ageing. The mild extraction method was then applied to explore the relationship between total and (bio)available concentrations in soil and in A. icterica, over 7- or 28-day exposure time. This demonstrated the proportionality between epoxiconazole concentration in earthworm and available in soil (up to 96 %, with regression coefficient R ²?=?0.98). Sublethal effects on earthworm remained not significant.     

Influence of the amendment of corn straw on the degradation behaviour of the fungicide dithianon in soil

Degradation studies were conducted with the fungicide (14)C-dithianon under standard conditions for 64 days in soil. The compound is characterized by mineralization losses of approx. 33% and the formation of non-extractable (bound) residues of approx. 63% in 64 days. The microbial activity of the soil was stimulated by an amendment of corn straw simulating post-harvest conditions. This addition of straw decreased the mineralization of the compound initially. At the end of the incubation period, however, the mineralization rate was higher in the straw amended soil compared to the control. The addition of straw increased the amount of radiocarbon in the desorption solutions. Thus higher amounts of incorporated radiocarbon could be found in the biomass of the amended soil. Model calculations show that the straw amendment has a sustained influence on the mineralization of the compound. Potential mechanisms of the effect of dissolved organic matter on the sorption/desorption equilibrium are discussed.     

Removal of Cu and Pb by tartaric acid modified rice husk from aqueous solutions

A study on the modification of rice husk by various carboxylic acids showed that tartaric acid modified rice husk (TARH) had the highest binding capacities for Cu and Pb. The carboxyl groups on the surface of the modified rice husk were primarily responsible for the sorption of metal ions. A series of batch experiments using TARH as the sorbent for the removal of Cu and Pb showed that the sorption process was pH dependent, rapid and exothermic. The sorption process conformed to the Langmuir isotherm with maximum sorption capacities of 29 and 108 mg/g at 27 +/- 2 degrees C for Cu and Pb, respectively. The uptake increased with agitation rate. Decrease in sorbent particle size led to an increase in the sorption of metal ions and this could be explained by an increase in surface area and hence binding sites. Metal uptake was reduced in the presence of competitive cations and chelators. The affinity of TARH for Pb is greater than Cu.     

Sorption of lead in soil as a function of pH: a study case in México

Reactions of lead sorption onto soil are largely affected by properties and composition of soil and its solution. In this study, the lead sorption onto regosol eutric soil from Francisco I. Madero, Zacatecas, Mexico is evaluated at different pH values. Soil samples were suspended in lead solutions of 10, 25, 50, 100, 150, 200, 300, and 400 mg/l (as Pb(NO3)2). The pH was adjusted at 2, 3, 4, and 5.5 with nitric acid for each of the lead solution concentrations. In all the cases the ionic strength was I=0.09 M with calcium nitrate. The solid-liquid-ratios were fixed in 1:100 and 1:200 g/ml. The results show that lead sorption increases when pH increases. Experimental isotherms were adjusted by both Langmuir and Freundlich models. The Langmuir affinity parameter, K, indicates that the lead sorption capacity of Francisco I. Madero soils is largely perceptible to pH changes.     

Synthesis and optimization of spherical nZVI (20–60 nm) immobilized in bio-apatite-based material for efficient removal of phosphate: Box-Behnken design in a fixed-bed column

In the present study, bio-apatite/nZVI composite was synthesized through Fe(III) reduction with sodium borohydride and was fully characterized by FTIR, XRD, SEM–EDX, TEM, BET, BJH, and pH_PZC. Column experiments were carried out for the removal of phosphate as a function of four operational parameters including initial phosphate concentration (100–200 mg L^?1), initial solution pH (2–9), bed height (2–6 cm), and influent flow rate (2.5–7.5 mL min^?1) using a response surface methodology (RSM) coupled with Box-Behnken design (BBD). 2D contour and 3D surface plots were employed to analyze the interactive effects of the four operating parameters on the column performance (e.g., uptake capacity and saturation time). According to ANOVA analysis, the influent flow rate and bed height are the most important factor on phosphate uptake capacity and saturation time, respectively. A quadratic polynomial model was excellently fitted to experimental data with a high coefficient of determination (>?0.96). The RSM-BBD model predicted maximum phosphate adsorption capacity of 85.71 mg g^?1 with the desirability of 0.995 under the optimal conditions of 135.35 mg L^?1, 2, 2 cm, and 7.5 mL min^?1 for initial phosphate concentration, initial solution pH, bed height, and influent flow rate, respectively. The XRD analysis demonstrated that the reaction product between bio-apatite/nZVI composite and phosphate anions was Fe₃ (PO₄)₂. 8H₂O (vivianite). The suggested adsorbent can be effectively employed up to five fixed-bed adsorption–desorption cycles and was also implemented to adsorb phosphate from real samples.

     

Sorptive behavior of sorgoleone in ultisol in two solvent systems and determination of its lipophilicity

Sorgoleone (SGL) exuded by sorghum roots inhibits the development of some weeds. Due to its high hydrophobicity, it is expected that SGL presents low soil mobility and limited allelopathic activity in the field. This work aims to evaluate the sorptivity of sorgoleone in octanol-water and in soil under two solvent systems. The two solvent systems were methanol:water (60:40) (MeOH:H2O) and pure methanol (MeOH). These two solvent systems promote different conditions for SGL solubility. Treatments were arranged in a 2 x 6 factorial (solvent systems x equilibrium concentrations in the solution (EC)). For each solvent, the sorption was achieved by shaking 500 mg of soil with 10 ml of 0, 5, 10, 15, 25, 40, and 60 mg L-1 of SGL solution, during 24 h. After centrifugation, the supernatant was filtered and the SGL concentration was determined by high performance liquid chromatography (HPLC). Data of sorbed amount of SGL were submitted to variance analysis, using a hierarchic factorial model. The data of sorbed amount (x/m) and equilibrium concentration (C) were fitted to the linear (x/m = a + KdC) and to the Freundlich (x/m = KfC1/n) models. The isotherm obtained for the MeOH:H2O system presented linear shape, whereas for the MeOH system a two subsequent linear isotherm was fitted. Sorgoleone is a highly hydrophobic compound, presenting a log Kow of 6.1. The sorption of sorgoleone to the soil was very high. The organic environment stimulated the sorgoleone sorption to the soil.