Aggregate stabilization in kaolinitic soils by low rates of anionic polyacrylamide

Abstract. The stability of aggregates can be improved by amending the soil with charged synthetic polymers. We have evaluated the effects of addition of low rates of anionic polyacrylamide (PAM) on the stability of aggregates from three predominately kaolinitic soils, and investigated whether the applied PAM penetrated into the aggregates or was adsorbed onto exterior surfaces only. Aggregates (6.3–9.5 mm) from the Ap horizons of a Cecil sandy loam and a Cecil loamy sand (Typic Kanhapludult) and from the Bt horizon of a Davidson clay (Rhodic Kandiudult) were treated with a high molecular weight(2 × 10⁷Da), negatively charged (20% hydrolysis) PAM at rates of 0, 10 or 20 kg/ha. The treated aggregate were dried and exposed to 20 mm of high kinetic energy (23.0 kJ/m³) simulated rain. Some of the PAM-treated Cecil loamy sand aggregates (5 or 10 kg/ha) were broken in half to expose untreated aggregate interiors to the rain. Percentage stable aggregates (weight/weight) in the PAM treatments ranged from 52 to 97%, vs. 20-32% in the control. PAM addition significantly increased the percentage of >4 mm sized aggregates compared with the untreated aggregates. PAM was more effective at stabilization in the light to medium textured Cecil soils than in the clayey Davidson. When internal surfaces of PAM treated aggregates were exposed, the percentage of stable aggregates exceeded the amount expected if the polymer was only adsorbed on to external surfaces. This suggested that some PAM had penetrated to some degree into aggregate interiors, thereby stabilizing both external and internal aggregates surfaces. Based on these results it is envisaged that use of PAM could be a viable alternative to the commonly used soil and water conservation practices (e.g. mulching, dyking, contour tillage).     

改性膨胀珍珠岩去除废水中磷酸盐的研究

采用膨胀珍珠岩经过镧系稀土金属元素改性后处理了含磷废水。结果表明:改性后的膨胀珍珠岩对废水中的磷酸盐有明显的去除效果,当废水pH值为6~9,磷浓度为25mg/L,按改性膨胀珍珠岩与磷质量比为50:1来处理含磷废水,反应时间在4h之内,剩余磷酸盐的浓度小于0.5mg/L,磷酸盐的去除率达97%以上。     

Retention of Molybdenum(VI) by Three Finnish Mineral Soils

Abstract

Retention of molybdate by three Finnish mineral soils from 10^?4 and 10^?5 M sodium molybdate solutions at room temperature was investigated at pH 2.3–7.5. In the adsorption experiments 0.02 M KCl was used as ionic medium, and the samples were left to equilibrate for 72 h. The solid: solution ratio was 1:100 (w: v). Maximum adsorption occurred below pH 4.5, where about 60–80 % of added molybdenum was retained. Desorption of the adsorbed molybdenum was measured by adding 50 ml of 0.02 M KCl into weighed soil samples and shaking for 17 h in an apparatus with a mechanical stirrer. In each soil an appreciable amount of Mo was so tightly bound that it could not be removed by KCl treatment.     

电选法回收废印刷线路板中金属Cu的研究

采用破碎机和高压电选机对废印刷线路板中金属Cu进行回收.结果表明,破碎产物粒度<0.9mm时金属的单体解离度较高,可以作为分选的原料.物料在电选过程中的动力学分析表明,影响电选效果的主要因素为电极电压、滚筒转速、电晕电极距及物料粒度.经正交实验优化影响参数后,-0.9+0.074mm粒级的破碎产物一次电选所得精料中Cu的富集情况较好,Cu品位由32.0%富集到63.6%,回收率为78.7%.     

活性炭C40/4吸附甲苯和丙酮吸附性能研究

为探讨活性炭吸附C40／4有机蒸汽的性能曲线规律，在不同温度288．15K，293．15K和298．15K下实验测试了活性炭C40／4吸附有机气体甲苯和丙酮的吸附性能，基于langmuir等温吸附理论，从吸附动态平衡的角度，理论分析了吸附性能曲线中参数与温度之间的关系，提出一个经验的langmuir等温吸附曲线模型，它能很好地描述不同温度下的有机蒸汽在活性炭上的吸附性能曲线，模型计算值与实验测试值之间的误差小于6％，为确定活性炭吸附有机蒸汽的吸附量提供了有效的计算模式，从而为有机蒸汽吸附过程的设计、预测和优化提供有益的支持。     

Behaviour of some pesticides in a nutrient-film and in a rock-wool system

Adsorption of ethoprophos, tetrachlorvinphos and etridiazole onto rock-wool was found to be much weaker than adsorption onto soils. The rates of transformation in water and in water plus rock-wool at 20°C were low. The concentration of etridiazole was measured in a nutrient-film system with recirculating nutrient solution. The decrease was rapid in the first few hours but was more gradual afterwards, to low values at 8 days after application. Etridiazole penetrated poorly into the lower part of a rock-wool system when the solution was trickled near the stem-base of the tomato plants.     

高压静电技术在食品保鲜与加工中的研究进展

介绍了高压静电场技术对食品的作用机理。阐述了静电场技术在食品保鲜、干燥、杀菌和解冻等方面的研究现状。     

杨树根际土壤磷吸附特性的研究

对滨海脱盐土壤上11年生1-69杨根际、非根际土壤磷吸附特性进行了研究。结果表明,I-69杨根系活动能抑制根际土壤对磷的吸附,抑制能力与培养溶液起始磷浓度相关,当培养溶液起始磷浓度为30 mg／L时,抑制能力最大,根际、非根际土壤磷吸附量之差为-15．57 mg／kg;I-69杨根际、非根际土壤磷恒温吸附数据都能很好地用一元 Langmuir方程、Freundich方程和Temkin方程拟合,其中一元Langmuir方程拟合最好;根际土壤磷吸附容量参数Xm,k, k1,k2的值明显低于非根际土壤,相关分析表明,它们与土壤有效磷含量呈显著负相关。     

塿土不同粒级组分K+吸附研究

土各粒级K+吸附特征有很大区别.在一定平衡液浓度下,颗粒越细,土壤固相吸附量越大,不同粒级固相吸附量大小顺序是(＜0.1m)＞(＜1m)＞(1～2m)＞(2～5m),不同粒级土壤有效阳离子交换量也具有相同的变化规律.混合样中不同粒级组分对吸附的贡献可用吸附贡献率表示,土各粒级饱和吸附贡献率大小顺序为(＜1m)＞(1～2m)＞(＞5m)＞(2～5m),其中粘粒部分的饱和吸附贡献率为85%左右.在供试混合土样中＜1m粒级吸附贡献率随平衡液浓度增大呈幂函数形式增大,相反,1～2m、2～5m粒级吸附贡献率随平衡液浓度增大则呈幂函数形式减小.实验证明混合样中不同粒级K+吸附存在交互作用,吸附交互作用大小可用吸附交互作用系数表征,＜1m和1～2m之间存在吸附负交互作用,且随平衡液浓度增大而增强.＜1m和2～5m之间存在吸附正交互作用,且随平衡液浓度增大而减弱.论述了建立土壤多粒级组分吸附方程的必要性,提出了多粒级组分吸附方程q＝ρ(c)rifi(c)