Removal of pesticides from rinsate by adsorption using agricultural residuals as medium

Abstract

The feasibility of using agricultural residual with highly organic matter content ‐ spent mushroom compost (SMC) as adsorption medium for removal of pesticides including carbaryl, carbofuran, and aldicarb with a concentration range of 0–30 mg/L from rinsate was investigated. Bottle‐point method was used to determine adsorption isotherms for single‐pesticide and multi‐pesticides. It was found that SMC might potentially be used for on‐farm treatment of pesticide rinsate. The adsorption capacity of SMC was increased compared to most soils, possibly related to the increased organic matter content. The rapid equilibrium of pesticide solution and SMC was consistent with a physical type of adsorption mechanism. The adsorption of carbamate pesticides on SMC was found to exhibit nonlinear “favorable”; adsorption behavior that could be characterized well by the Freundlich isotherm model. In addition, the multi‐pesticide adsorption tests displayed the characteristics of competitive behavior. The competitive ability of these three pesticides in multi‐components adsorption was in the order carbaryl > carbofuran > aldicarb, which was consistent with the adsorbability of pesticides.     

A comparative study for the sorption of Cd(II) by K-feldspar and sepiolite as soil components, and the recovery of Cd(II) using rhamnolipid biosurfactant

This study investigated the sorption characteristics and recovery of selected heavy metal Cd(II) from K-feldspar and sepiolite, representative soil components, using rhamnolipid biosurfactant. Although the proposed technique was classified as a soil bioremediation process, it can also be applied to treatment of waste waters containing Cd(II) ions with minor modifications. The effect of initial Cd(II) concentration on sorption capacity was characterized by determining the sorption isotherms. Of the four models examined, the Freundlich model showed the best fit for the sorption of Cd(II) on K-feldspar, whereas the Langmuir-model was used successfully to characterize the sorption of Cd(II) on sepiolite. Although a high Cd(II) uptake of 7.49 mmol/kg by K-feldspar was obtained, sepiolite was a superior Cd(II) accumulater, with a maximum Cd(II) uptake of 24.66 mmol Cd(II)/kg. The presence of Cd(II) in the sepiolite or K-feldspar prior to addition of the rhamnolipid generally resulted in less rhamnolipid sorption to sepiolite or K-feldspar. The maximum Cd(II) desorption efficiency by rhamnolipid from K-feldspar was substantially higher than that of sepiolite and determined to be 96% of the sorbed Cd(II), whereas only 10.1% of the sorbed Cd(II) from sepiolite was recovered by rhamnolipid solution.     

雌二醇在土壤/沉积物中的吸附特征及猪粪DOM对吸附的影响

天然类固醇雌激素如17β-雌二醇(E2)在极低质量浓度下(ng.L-1)即可干扰水生生物的生殖功能.为准确预测E2向水体迁移,通过摇床实验研究了E2在中国北方3种不同土壤/沉积物表面的吸附特征,同时探讨了猪粪及其堆肥可溶态有机质(DOM)对E2吸附的影响.结果发现,E2在土壤/沉积物表面吸附符合Freundlich等温吸附方程(R2>0.76),E2在河流沉积物、潮土、黑土皆表现为非线性,其中黑土吸附的非线性最强(n=0.74);吸附系数Kf介于26.2～57.5,并与有机质含量呈显著正相关(P<0.05).猪粪及其堆肥DOM显著抑制E2在土壤/沉积物表面的吸附,其中堆肥DOM的影响尤为显著.研究认为,有机质是土壤/沉积物中吸附E2的主要组分,共存猪粪DOM在较低浓度下可提高E2迁移性,增加E2向地表和地下水的迁移风险.     

Removal of toxic chromium(VI) from aqueous solution by activated carbon using Casuarina equisetifolia

Highly activated carbon from the seed husk of Casuarina Casuarinas equisetifolia, a worldwide famous plant, have been prepared and tested for the removal of toxic Cr(VI) from its aqueous solution. The adsorbent was investigated for influences of initial chromium concentration (75, 100, 125, and 150 mg l^-1), pH, contact time, and quantity of carbon on removal of Cr(VI) from aqueous solution at room temperature (25±2 °C). The adsorption kinetic of Cr(VI) was studied, and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R²≥0.99). The Langmuir and Freundlich models fit the isotherm data well. Furthermore, the Gibbs free energy was obtained for each system and was found to be-5.29 kJ mol^-1 for removal of Cr(IV). The negative value of Δ G° indicates the feasibility and spontaneous nature of adsorption. The results indicate that acidic pH (1.05) supported the adsorption of Cr(IV) on activated carbon. The maximum adsorption capacity of Cr(VI) on activated carbon was about 172.4 mg g^-1 at pH 1.05.     

活性炭吸附处理黄磷化工渗滤液研究

研究了颗粒活性炭对黄磷化工渗滤液中有机物的吸附容量、吸附热力学和动力学。结果表明:颗粒活性炭对渗滤液中有机物的吸附容量几乎不受渗滤液pH值的影响,吸附45min后基本达到平衡。吸附等温线更符合修正的Freundlich模型,表明实验中的吸附主要是多分子层的吸附。拟二级动力学模型能更好的定量描述有机物在颗粒活性炭上的吸附过程,速率常数k2=0.12128g/(mg·min),平衡吸附量qe=5.78748mg/g。     

Adsorption‐desorption hysteresis of α‐endosulfan in tropical soils using isotopic techniques

This study was designed to evaluate the adsorption‐desorption hysteresis of endosulfan (1,2,3,4, 7,7‐hexachlorobicyclo[2,2,1]‐2‐heptene‐5,6‐bisoxymethylene sulfite) in selected tropical soils. Two major tropical soils from Thailand were selected, Rangsit lowland soils (Rangsit series) and Phrabat upland soils (Pakchong series). The soil types were sub‐divided into plow soils, 0–20cm depth from the surface, and subsoils, 20–40cm depth. Adsorption was determined in 24h batch equilibrium, with five different concentrations of ¹⁴C endosulfan ranging from 1.04 to 16.64 ng/mg soils. Four successive desorption studies were performed continuously after three adsorption concentrations, 24h for each successive. Adsorption coefficient values (K _ads) as determined by Freundlich model ranged from 0.02 to 0.14 and found to be higher in Rangsit soils as expected when compared with Phrabat soils. Desorption was hysteresis in every desorption study. Desorption coefficient values (K _des) were higher than adsorption (K _des).     

颗粒物微界面吸附模型的分形修正--朗格缪尔(Langmuir)、弗伦德利希(Freundlich)和表面络合模型

运用分形理论修正了颗粒物微界面吸附模型,建立了朗格缪尔(Langmuir)、弗伦德利希(Freundlich)和表面络合模型的分形吸附等温线方程式．其中,朗格缪尔(Langmuir)吸附等温线的分形表达式为：Γ=ΓmCc^1/m／(b^m Cc^1/m),指数m与颗粒物表面分维Ds的关系如下：m∝ac^D/2-1∝ro^Do-2;表面络合模型的分形表达式为：Γ=ΓmCs^(n/x)/(b^(n/x) Cs^(n/x)),而且lgb=lg(ks／kb) pH,指数x／n与颗粒物表面分维Ds的关系如下：x／n∝0^D/2-1∝r0^D-2;相应的弗伦德利希(Freundlich)吸附等温线的分形形式分别为：Γ=(Γm／bm)Cs^1/n,Γ=(Γm／b^(x/n))Cr^(n/x),通过对献中的数据的模拟初步讨论了分形模型的适用性,结果表明,它们具有更接近于实际的描述微界面吸附过程的能力,通过lg(x／n)=lgk’ (Dn-2)lgro计算出土壤颗粒和尾矿砂颗粒的表面分形维数分别为2．42和2．72。     

外源硅对土壤镉吸附特性的影响

通过吸附等温试验,研究了不同加入量的硅对两种水田土壤吸附镉特性的影响。实验中调节介质的pH值至中性,从而消除了因硅酸盐的加入对土壤pH产生的影响。结果表明:在硅的加入量相同时,pH值较低的土壤对镉的吸附量要低于pH值较高的土壤;镉的加入质量浓度为0～50mg·L-1时,应用Freundlich方程拟合土壤对镉的吸附等温线效果最好;外源硅的加入量在0～120mg·L-1范围内时,随硅的加入量的增加土壤对镉的吸附量会有不同程度的降低。由此推断,对于以往研究发现的外源硅能够降低土壤镉的有效性、缓解植物的镉毒害作用,并非是促进了土壤对镉的吸附,而是可能存在着其他机制,这有待于进一步研究。     

粉煤灰的改性及其对高盐苯胺废水的处理

以盐酸和硫酸作为改性剂,对粉煤灰进行改性。通过正交实验得到最佳改性粉煤灰制备条件为：V（盐酸）∶V（硫酸）=1∶5,浸泡时间6h,活化时间6h,活化温度250℃。在初始苯胺质量浓度为200mg/L、氯化钠质量分数为15%、吸附时间为60min的条件下,采用在最佳条件下制备得到的改性粉煤灰对苯胺进行吸附,吸附量可达4.16mg/g。采用Freundlich方程可更好地对改性粉煤灰吸附苯胺的过程进行拟合。     

Activated carbons derived from oil palm empty-fruit bunches： Application to environmental problems

Activated carbons derived from oil palm empty fruit bunches （EFB） were investigated to find the suitability of its application for removal of phenol in aqueous solution through adsorption process, Two types of activation namely; thermal activation at 300, 500 and 800℃and physical activation at 150℃ （boiling treatment） were used for the production of the activated carbons. A control （untreated EFB） was used to compare the adsorption capacity of the activated carbons produced from these processes. The results indicated that the activated carbon derived at the temperature of 800℃ showed maximum absorption capacity in the aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon at 800℃. It was observed that the adsorption capacity was higher at lower values of pH （2-3） and higher value of initial concentration of phenol （200-300 mg/L）. The equilibrium data fitted better with the Freundlich adsorption isotherm compared to the Langmuir. Kinetic studies of phenol adsorption onto activated carbons were also studied to evaluate the adsorption rate. The estimated cost for production of activated carbon from EFB was shown in lower price （USD 0.50/kg of activated carbon） compared the activated carbon from other sources and processes.