Sorption of metolachlor and atrazine in fly ash amended soils: comparison of optimized isotherm models

Adsorption of metolachlor and atrazine was studied in the fly ash (Inderprastha and Badarpur)- amended Inceptisol and Alfisol soils using batch method. Results indicated that sorption of both the herbicides in soil+fly ash mixtures was highly nonlinear and sorption decreased with a higher herbicide concentration in the solution. Also, nonlinearity increased with an increase in the level of fly ash amendment from 0-5%. Three two-parameter monolayer isotherms viz. Langmuir, Temkin, Jovanovic and one imperical Freundlich models were used to fit the experimental data. Data analysis and comparison revealed that the Temkin and the Freundlich isotherms were best-suited to explain the sorption results and the observed and the calculated adsorption coefficient values showed less variability. The study suggested that sorption mechanism of metolachlor and atrazine involved the physical association at the sorbate surface and the nonlinearity in the sorption at higher pesticide or fly ash concentration was due to a decrease in the heat of adsorption and higher binding energy.     

Kinetic and isotherm error optimization studies for adsorption of atrazine and imidacloprid on bark of Eucalyptus tereticornis L.

The aim of this study was to establish the bark of Eucalyptus tereticornis L. (EB) as a low cost bio-adsorbent for the removal of imidacloprid and atrazine from aqueous medium. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD) models were used to describe the kinetic data and rate constants were evaluated. Adsorption data was analysed using ten 2-, 3- and 4-parameter models viz. Freundlich, Jovanovic, Langmuir, Temkin, Koble–Corrigan, Redlich–Peterson, Sips, Toth, Radke–Prausnitz, and Fritz-Schluender isotherms. Six error functions were used to compute the best fit single component isotherm parameters by nonlinear regression analysis. The results showed that the sorption of atrazine was better explained by PSO model, whereas the sorption of imidacloprid followed the PFO kinetic model. Isotherm model optimization analysis suggested that the Freundlich along with Koble–Corrigan, Toth and Fritz-Schluender were the best models to predict atrazine and imidacloprid adsorption onto EB. Error analysis suggested that minimization of chi-square (χ²) error function provided the best determination of optimum parameter sets for all the isotherms.     

Effect of fly ash on sorption behavior of metribuzin in agricultural soils

This investigation was undertaken to determine the effect of two different fly ashes [Kota and Inderprastha (IP)] amendment on the sorption behavior of metribuzin in three Indian soil types. The IP fly ash was very effective in increasing the metribuzin sorption in the soils. The sorption with IP amendment was increased by 15-92%, whereas with the Kota fly ash an increase in sorption by 13-38% was noted. The adsorption isotherms fitted very well to the Freundlich adsorption equation and, in general, slope (1/n) values less then unity were observed. Although both the fly ashes significantly decreased metribuzin desorption, the IP fly ash was comparatively more effective in retaining metribuzin in the soils. Metribuzin sorption in the IP fly ash-amended soils showed strong correlation with the fly ash content and compared to K(f)/K(d) values, K(FA) values (sorption normalized to fly ash content) showed less variation. Metribuzin sorption-desorption did not correlate to the organic carbon content of the soil-fly ash mixture. The study demonstrates that all coal fly ashes may not be effective in enhancing the sorption of metribuzin in soils to the same extent. However, among the fly ashes used in this study, the IP fly ash was observed to be significantly effective in enhancing the sorption of metribuzin in soils. This may play an important role in reducing the run off and leaching losses of the herbicide by retaining it in the soil.     

Effect of fly ash on metsulfuron-methyl sorption and leaching in soils

This investigation was undertaken to determine the effect of amendment of two fly ashes [Kota and Inderprastha (IP)] on sorption behavior of metsulfuron-methyl in three Indian soil types. Kota fly ash (5%) did not show any effect on herbicide sorption while IP fly ash significantly enhanced the sorption. Further studies on metsulfuron-methyl sorption-desorption behavior in 0.5, 1, 2, and 5% IP fly ash-amended soils suggested that effect of fly ash varied with soil type and better effect was observed in low organic carbon content soils. The sorption-desorption isotherms fitted very well to the Freundlich sorption equation and, in general, slope (1/n) values less than unity were observed. Metsulfuron-methyl sorption in the IP fly ash-amended soils showed strong correlation with the fly ash content and compared to the Freundlich sorption constant (K _f), K _FA values (sorption normalized to fly ash content) showed less variation. Metsulfuron-methyl leaching studies suggested greater retention of herbicide in the application zone in IP fly ash-amended soils, but effect varied with soil type and no herbicide leaching was observed in 5% fly ash-amended soils. The study suggested that all coal fly ashes are not effective in enhancing the sorption of metsulfuron-methyl in soils. However, one which enhanced herbicide sorption, could play an important role in reducing its leaching losses.     

Effect of fly ash on sorption behavior of metribuzin in agricultural soils

This investigation was undertaken to determine the effect of two different fly ashes [Kota and Inderprastha (IP)] amendment on the sorption behavior of metribuzin in three Indian soil types. The IP fly ash was very effective in increasing the metribuzin sorption in the soils. The sorption with IP amendment was increased by 15–92%, whereas with the Kota fly ash an increase in sorption by 13–38% was noted. The adsorption isotherms fitted very well to the Freundlich adsorption equation and, in general, slope (1/n) values less then unity were observed. Although both the fly ashes significantly decreased metribuzin desorption, the IP fly ash was comparatively more effective in retaining metribuzin in the soils. Metribuzin sorption in the IP fly ash-amended soils showed strong correlation with the fly ash content and compared to K_f/K_d values, K_FA values (sorption normalized to fly ash content) showed less variation. Metribuzin sorption-desorption did not correlate to the organic carbon content of the soil-fly ash mixture. The study demonstrates that all coal fly ashes may not be effective in enhancing the sorption of metribuzin in soils to the same extent. However, among the fly ashes used in this study, the IP fly ash was observed to be significantly effective in enhancing the sorption of metribuzin in soils. This may play an important role in reducing the run off and leaching losses of the herbicide by retaining it in the soil.     

粉煤灰对水溶液中磷的吸附性能及机理

以粉煤灰为吸附剂去除溶液中的磷,考察了其吸附除P动力学特征、热力学特征以及溶液初始pH和粉煤灰投加量对吸附除P效果的影响,并对其吸附除P机理做了初步探讨。结果表明,在给定实验条件下,粉煤灰对P具有较好的去除效果,随着初始P浓度从10 mg/L升高到80 mg/L,平衡吸附量为0.46～2.44 mg P/g粉煤灰,吸附效率从92.2%降低至61.1%;对不同浓度的含P溶液,粉煤灰最适用量为0.6～1.5 g粉煤灰/mg P;相同反应条件下,当温度由25℃升高到45℃时,P初始吸附速率提高了3倍;粉煤灰对P的吸附过程能够较好地拟合Langmuir、Freundlich及D-R吸附等温模型,相关系数均在0.98以上。通过对吸附饱和的粉煤灰进行解析实验发现,初始P浓度较低(<50 mg/L)时,以化学吸附为主,而在初始P浓度较高(>80 mg/L)时,则以物理吸附为主。     

Agro-waste biosorbents: Effect of physico-chemical properties on atrazine and imidacloprid sorption

Low cost agro-waste biosorbents namely eucalyptus bark (EB), corn cob (CC), bamboo chips (BC), rice straw (RS) and rice husk (RH) were characterized and used to study atrazine and imidacloprid sorption. Adsorption studies suggested that biosorbents greatly varied in their pesticide sorption behaviour. The EB was the best biosorbent to sorb both atrazine and imidacloprid with K_F values of 169.9 and 85.71, respectively. The adsorption isotherm were nonlinear in nature with slope (1/n) values <1. The Freundlich constant Correlating atrazine/imidacloprid sorption parameter [K_F.(1/n)] with the physicochemical properties of the biosorbents suggested that atrazine adsorption correlated significantly to the aromaticity, polarity, surface area, fractal dimension, lacunarity and relative C-O band intensity parameters of biosorbents. Probably, both physisorption and electrostatic interactions were responsible for the pesticide sorption. The eucalyptus bark can be exploited as low cost adsorbent for the removal of these pesticides as well as a component of on-farm biopurification systems.     

Kinetics and isotherm modeling of azoxystrobin and imidacloprid retention in biomixtures

The paper reports the kinetics and adsorption isotherm modeling for imidacloprid (IMIDA) and azoxystrobin (AZOXY) in rice straw (RS)/corn cob (CC) and peat (P)/compost (C) based biomixtures. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intraparticle diffusion models were used to describe the kinetics. The adsorption data were subjected to the Langmuir and the Freundlich isotherms. Results (r²_Adj values) suggested that the modified Elovich model was the best suited to explain the kinetics of IMIDA sorption while different models explained AZOXY sorption kinetics in different biomixtures (PFO in RS?+?C and RS?+?P; PSO in CC?+?P and Elovich in CC?+?C). Biomixtures varied in their capacity to adsorb both pesticides and the adsorption coefficient (K_d) values were 116.8–369.24 (AZOXY) and 24.2–293.4 (IMIDA). The Freundlich isotherm better explained the sorption of both pesticides. Comparison analysis of linear and nonlinear method for estimating the Freundlich adsorption constants was made. In general, r²_Adj values were higher for the nonlinear fit (AZOXY?=?0.938–0.982; IMIDA?=?0.91–0.970) than the linear fit (AZOXY?=?0.886–0.993; IMIDA?=?0.870–0.974) suggesting that the nonlinear Freundlich equation better explained the sorption. The rice straw-based biomixtures performed better in adsorbing both the pesticides and can be used in bio-purification systems.     

粉煤灰砖块对磷酸盐的吸附特性

以建筑废料粉煤灰砖块为吸附剂材料,通过静态吸附实验研究其对磷酸盐的吸附特征,以及磷酸盐初始浓度、吸附剂投加量、pH等因素对吸附反应的影响。Langmuir、Freundlich和Temkin等温模型的分析发现,Langmuir等温式方程最适合描述吸附过程,对磷酸盐的理论饱和吸附容量为44.62 mg/g。利用伪一级动力学模型、伪二级动力学模型和颗粒内扩散模型考察了吸附过程特征,其中伪二级动力学模型为最适于描述粉煤灰砖块对磷酸盐的吸附过程的动力学模型。通过颗粒内扩散模型、Bangham方程及Boyd模型对吸附动力学机理进行的探讨表明,颗粒内扩散速率不是粉煤灰砖块吸附磷酸盐反应的惟一速率控制步,膜扩散速率和颗粒内扩散速率共同影响着吸附反应速率。磷酸盐浓度较低时主要是膜扩散限制吸附反应速率,而磷酸盐浓度较高时则颗粒内扩散成为速率控制步。研究证明,粉煤灰砖块粉末作为湿地基质具有对磷酸盐很强的吸附能力,在减少了固体废弃物的数量的同时又可以实现水污染控制的目的。     

Phenol removal from wastewater by adsorption on zeolitic composite

It is well known that adsorption is an efficient method of removal of various pollutants from wastewater. The present study examines the phenol removal from water by adsorption on a new material, based on zeolitic volcanic tuff. This compound contains zeolitic tuff and cellulose, another known adsorbent, in a mass ratio of 4 to 1. The performances of the new adsorbent composite were compared with those of a widely used adsorbent material, zeolitic volcanic tuff. The adsorbent properties were tested on batch synthetic solutions containing 1–10 mg L^?1 (1–10 ppm) phenol, at room temperature without pH adjustment. The influence of the adsorbent dose, pH and contact time on the removal degree of phenol from water was investigated. The experimental data were modeled using the Langmuir, Freundlich, and Temkin adsorption isotherms. The Langmuir model was found to best represent our data revealing a monolayer adsorption with a maximum adsorption capacity between 0.12 and 0.53 mg g^?1 at 25 °C, for 2.00 g of adsorbent, depending on the initial phenol concentration. The adsorption kinetic study was performed using a pseudo-first- and pseudo-second-order kinetic models illustrating that phenol adsorption on zeolite composite is well described by pseudo-first kinetic equations. Our results indicated that phenol adsorption on the new adsorbent composite is superior to that on the classic zeolite.     

Adsorptive removal of an acid dye by lignocellulosic waste biomass activated carbon: equilibrium and kinetic studies

Chemically prepared activated carbon material derived from palm flower was used as adsorbent for removal of Amido Black dye in aqueous solution. Batch adsorption studies were performed for the removal of Amido Black 10B (AB10B), a di-azo acid dye from aqueous solutions by varying the parameters like initial solution pH, adsorbent dosage, initial dye concentration and temperature with three different particle sizes such as 100 μm, 600 μm and 1000 μm. The zero point charge was pH 2.5 and the maximum adsorption occurred at the pH 2.3. Experimental data were analyzed by model equations such as Langmuir, Freundlich and Temkin isotherms and it was found that the Freundlich isotherm model best fitted the adsorption data and the Freundlich constants varied from (K_F) 1.214, 1.077 and 0.884 for the three mesh sizes. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated for the adsorption processes and found that the adsorption process is feasible and it was the endothermic reaction. Adsorption kinetics was determined using pseudo first-order, pseudo second-order rate equations and also Elovich model and intraparticle diffusion models. The results clearly showed that the adsorption of AB10B onto lignocellulosic waste biomass from palm flower (LCBPF) followed pseudo second-order model, and the pseudo second-order rate constants varied from 0.059 to 0.006 (g mg⁻¹ min) by varying initial adsorbate concentration from 25 mg L⁻¹ to 100 mg L⁻¹. Analysis of the adsorption data confirmed that the adsorption process not only followed intraparticle diffusion but also by the film diffusion mechanism.     

Lead sorption in calcareous soils

The sorption of lead by three soils that differed in texture and calcium carbonate content was studied at three different temperatures. Lead sorption was found to conform to both Freundlich and Langmuir isotherms. Soil adsorption maxima were derived from the reciprocal of the slope obtained by a least-squares fit of Langmuir plots for each soil. The highest adsorption capacity was exhibited by CaCO(3)-rich soil (773.55 mmol Pb kg(-1)). Raising the temperature from 298 K to 308 and 318 K increased the sorption capacity of all of the soils.     

“氧化镁/活性炭”新型吸附剂的制备及其对Cr(VI)的吸附研究

以氯化镁和造纸草浆黑液为原料,采用物理活化法制得“氧化镁/活性炭”新型吸附剂,其比表面积（BET）为388.96 m²/g、总孔容积为0.40 mL/g。测定了这种吸附剂对水中Cr(VI)的吸附性能,考察了吸附时间、pH值、吸附剂投加量、初始浓度等因素对Cr(VI)的吸附量和脱除率的影响,研究所得吸附水溶液中Cr(VI)的最佳条件为：吸附时间为120 min,吸附剂投加量为2 g/L,pH值为2。“氧化镁/活性炭”新型吸附剂对Cr(VI)的吸附过程符合Freundlich等温式。     

改性玉米秸秆吸附Cu2+的动力学和热力学

本研究用ZnCl2作为活化剂,使用功率640 W的微波照射4 min的方法制备改性玉米秸秆。考察投加量、pH、吸附时间对吸附性能的影响,并对等温吸附特征、吸附动力学和热力学进行了系统研究。结果表明:投加量为0.2 g,pH为6,改性玉米秸秆对Cu2+具有很好的吸附效果,吸附在8 h后达到平衡。该吸附过程符合Langmuir及Freundlich等温吸附模型和准二级动力学方程,其反应的吉布斯自由能△G<0,为自发反应过程。     

Sorption of carbendazim and linuron from aqueous solutions with activated carbon produced from spent coffee grounds: Equilibrium,kinetic and thermodynamic approach

Spent coffee grounds (SCG) have been used for the production of activated carbon (AC) by impregnation with different ratios of phosphoric acid at 600?°C, Xp (H₃PO₄/coffee): 3:1^30%, 4:1^30%, 3:1^50% and 4:1^50%. The obtained AC was characterized by BET, FTIR and SEM. BET surface area corresponds to 803.422 m² g^?1. The influences of the main parameters such as contact time, the pesticides initial concentration, adsorbent dose, pH and temperature on the efficiency of separation process were investigated during the batch operational mode. Results were modeled by adsorption isotherms: Langmuir, Freundlich and Temkin isotherms, which gave satisfactory correlation coefficients. The maximum adsorption capacities calculated from the Langmuir isotherms were 11.918?mg g^?1 for carbendazim and 5.834?mg g^?1 for linuron at room temperature. Adsorption kinetics of carbendazim and linuron have been studied by the pseudo-first-order, the pseudo-second-order and the intraparticle diffusion model. The results of adsorption kinetics have been fitted the best by pseudo-second-order model. The resulted data from FTIR characterization pointed to the presence of many functional groups on the AC surface. SCG adsorbent, as an eco-friendly and low-cost material, showed high potential for the removal of carbendazim and linuron from aqueous solutions.     

改性玉米秸秆吸附Cu^2＋的动力学和热力学

本研究用ZnCl2作为活化剂,使用功率640W的微波照射4min的方法制备改性玉米秸秆。考察投加量、pH、吸附时间对吸附性能的影响,并对等温吸附特征、吸附动力学和热力学进行了系统研究。结果表明：投加量为0．2g,pH为6,改性玉米秸秆对Cu^2＋具有很好的吸附效果,吸附在8h后达到平衡。该吸附过程符合Langmuir及Freundlich等温吸附模型和准二级动力学方程,其反应的吉布斯自由能△G〈0,为自发反应过程。     

Sorption kinetics and isotherm modelling of imidacloprid on bentonite and organobentonites

Bentonite was modified by quaternary ammonium cations viz. cetytrimethylammonium (CTA), cetylpyridinium (CP), rioctylmethylammonium (TOM) and pcholine (PTC) at 100% cation exchange capacity of bentonite and was characterized by X-ray diffraction, CHNS elemental analyser and Fourier transform infrared spectroscopy. The sorption of imidacloprid on organobentonites/bentonite was studied by batch method. Normal bentonite could adsorb imidacloprid only upto 19.31–22.18% while all organobentonites except PTC bentonite (PTCB), enhanced its adsorption by three to four times. Highest adsorption was observed in case of TOM bentonite (TOMB) (76.94–83.16%). Adsorption kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. For normal bentonite data were best fitted to pseudo-first-order kinetic, while for organobentonites fitted to pseudo-second-order kinetics. Sorption data were analysed using Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherm models. Data were well fitted to Freundlich adsorption isotherm. Product of Freundlich adsorption constant and heterogeneity parameter (K_f.1/n) was in following order: TOMB (301.87) > CTA bentonite (CTAB) (152.12) > CP bentonite (CPB) (92.58) > bentonite (27.25). Desorption study confirmed hysteresis and concentration dependence. The present study showed that the organobentonite could be a good sorbent for removal of imidacloprid from natural water sample also. Percentage adsorption and Distribution coefficient (mL g^?1) value of different adsorbent was in following order: TOMB (74.85% and 297.54) > CTAB (55.78% and 126.15) > CPB (45.81% and 84.55) > bentonite (10.65% and 11.92).     

“氧化镁/活性炭”新型吸附剂的制备及其对Cr（Ⅵ）的吸附研究

以氯化镁和造纸草浆黑液为原料,采用物理活化法制得＂氧化镁/活性炭＂新型吸附剂,其比表面积（BET）为388.96 m2/g、总孔容积为0.40 mL/g。测定了这种吸附剂对水中Cr（Ⅵ）的吸附性能,考察了吸附时间、pH值、吸附剂投加量、初始浓度等因素对Cr（VI）的吸附量和脱除率的影响,研究所得吸附水溶液中Cr（Ⅵ）的最佳条件为：吸附时间为120min,吸附剂投加量为2 g/L,pH值为2。＂氧化镁/活性炭＂新型吸附剂对Cr（Ⅵ）的吸附过程符合Freundlich等温式。     

Removal of acutely hazardous pharmaceuticals from water using multi-template imprinted polymer adsorbent

Molecularly imprinted polymer adsorbent has been prepared to remove a group of recalcitrant and acutely hazardous (p-type) chemicals from water and wastewaters. The polymer adsorbent exhibited twofold higher adsorption capacity than the commercially used polystyrene divinylbenzene resin (XAD) and powdered activated carbon adsorbents. Higher adsorption capacity of the polymer adsorbent was explained on the basis of high specific surface area formed during molecular imprinting process. Freundlich isotherms drawn showed that the adsorption of p-type chemicals onto polymer adsorbent was kinetically faster than the other reference adsorbents. Matrix effect on adsorption of p-type chemicals was minimal, and also polymer adsorbent was amenable to regeneration by washing with water/methanol (3:1, v/v) solution. The polymer adsorbent was unaltered in its adsorption capacity up to 10 cycles of adsorption and desorption, which will be more desirable in cost reduction of treatment compared with single-time-use activated carbon.     

盐泥吸附剂对直接染料的平衡吸附行为和热力学性质研究

以染料废水处理用盐泥吸附剂的开发为目的,在静态吸附条件下,研究了含镁盐泥对直接大红、直接深蓝和直接黑3种直接染料的吸附行为,并对吸附过程的热力学进行了分析。结果表明,吸附平衡数据都能够较好地符合Langmuir和Freundlich吸附等温方程,但Langmuir方程能够更好地描述吸附等温线。在25～30℃范围内,3种直接染料在盐泥上的吸附是一个吸热过程,同时伴随着熵值的增加,反应的吉布斯自由能变小。吸附是物理和化学吸附并存的吸附过程,主要推动力为化学键力（化学吸附）,同时可能存在范德华力（物理吸附）,吸附焓变在74120～87332 kJ/mol之间。