Effect of Saline Water on Soil Acidity, Alkalinity and Nutrients Leaching in Sandy Loamy Soil in Rwamagana Bella Flower Farm, Rwanda

The necessity to saline and sodic waters is sometimes used for irrigating agricultural activities under certain circumstances, but it is important to note that the use of these waters comes with specific considerations and limitations. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments within the soil. This study aimed to assess the effectiveness of saline water on soil acidity, alkalinity and nutrients leaching in sandy loamy soil at Bella flower farm, in Rwamagana District, Rwanda. The water used was from the Muhazi Lake which is classified as Class I (Saline water quality). Column leaching experiments using treated soils were then conducted under saturated conditions. The soil under experimental was first analyzed for its textural classification, soil properties and is classified as sandy loamy soil. The t-test was taken at 1%, 5% and 10% levels of statistical significance compared to control soil. The results indicated that the application of saline water to soils caused an increase in some soil nutrients like increase of Phosphorus (P), Potassium (K+), Magnesium (Mg2+), Sulphur (S), CN ratio and Sodium (Na+) and decreased soil texture, physical and chemical properties and remained soil nutrients. Consequently, the intensive addition of saline water leachates to soil in PVC pipes led to decreased of soil EC through leaching and a raiser Soluble Sodium Percentage (SSP). The rate of saline water application affected the increase accumulation of SAR and Na% in the top soil layers. The study indicated that saline water is an inefficient amendment for sandy soil with saline water irrigation. The study recommends further studies with similar topic with saline water irrigation, as it accentuated the alkalinity levels.

Investigation of the Leaching Behavior of Mortar Pipe Lining in Drinking Water

The leaching behavior of three types of mortars was investigated using a self-design device which could simulate the field conditions of pipe lining. The results by ICP and ESEM measurement show that the developed slag cement mortar is suitable for the lining of cast iron pipe that is used for delivering drinking water.

Chlorination roasting-coupled water leaching process for potash recovery from waste mica scrap using dry marble sludge powder and sodium chloride

The present paper reports the effective utilization of marble sludge powder(MSP)for the recovery of potash values from waste mica scrap using chlorination roasting-water leaching method.Characterization studies indicated the presence of dolomite as the major mineral phase in MSP,whereas muscovite and quartz were observed in the mica sample.The acid leaching studies suggest a maximum of 22%potash recovery under conditions:4 M H2SO4 acid,particle size of^100μm,stirring speed of 600 r/min,leaching temperature of 75℃,and leaching time of 90 min.The chlorination roasting-water leaching process was adopted to achieve the lowest level of 80%-90%potash recovery.The optimum conditions for the recovery of^93%potash from mica(~8.6wt%K2O)requires 900℃ roasting temperature,30 min roasting time,and 1:1:0.75 mass ratio of mica:MSP:NaCl.The roasting temperature and amount of NaCl are found to be the most important factors for the recovery process.The reaction mechanism suggests the formation of different mineral phases,including sylvite(KCl),wollastonite,kyanite,and enstatite,during roasting,which were confirmed by X-ray diffraction(XRD)analyses and scanning electron microscopy(SEM)morphologies.The MSP-blended NaCl additive is more effective for potash recovery compared with the other reported commercial roasting additives.

Chromium leaching mechanism of coal mine water—a modeling study based on Xuzhou-Datun coal mine district

In order to investigate chromium contamination of coal mine water, to analyze chromium leaching mechanism and to evaluate environment pollution potential of coal mine water, we perform site investigations, physical and computer modeling in the Xuzhou-Datun coal mine district. The result of our test samples shows that chromium concentration was 9 μg/L in roof leachate and 3 μg/L in coal leachate. The host rock has a higher pollution potential than that of coal seams. Leaching experiments and XRD test results indicate that chromium is released from the process of transforming illite to kaolinite. The pH, pe and temperature of coal mine water affect the chromium leaching behavior. Modeling results suggest that the adsorption of adsorbents controls chromium concentration in coal mine water. The chromium adsorption ratio is quite low in both an acid and in an alkaline environment. Therefore, coal mine water has a high pollution potential. Under other conditions, chromium adsorption is stronger in a neutral water environment, so that chromium concentrations may be very low.

Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K_(2)CO_(3) roasting and water leaching followed by CaCl_(2) precipitation

Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)roasting and water leaching was investigated.The roasting and leaching conditions were optimized:the leaching efficiencies of vanadium and tungsten were 91.19%and 85.36%,respectively,when 18 equivalents of K_(2)CO_(3)were added to perform the roasting at 900℃ for 2 h,followed by leaching at 90°C for 1 h.Notably,in the described conditions,the leaching rate of silicon was only 28.55%.Titanates,including K_(2)Ti_(6)O_(13)and KTi8017,were also produced.Si removal was achieved in 85%efficiency adjusting the pH to 9.5,and the Si impurity thus isolated was composed of amorphous Si.Tungsten and vanadium were precipitated using CaCl_(2).At pH 10 and following the addition of 0.10 mol of H_(2)O_(2)and 16 equivalents of CaCl_(2),the precipitating efficiencies of tungsten and vanadium were 96.89%and 99.65%,respectively.The overall yield of tungsten and vanadium was 82.71%and 90.87%,respectively.

Extraction of metals from complex sulfide nickel concentrates by low-temperature chlorination roasting and water leaching

The recovery of valuable metals from complex sulfide concentrates was investigated via chlorination roasting followed by water leaching. A reaction process is proposed on the basis of previous studies and the results of our preliminary experiments. During the process,various process parameters were studied,including the roasting temperature,the addition of NH_4 Cl,the roasting time,the leaching time,and the liquid-to-solid ratio. The roasted products and leach residues were characterized by X-ray diffraction and vibrational spectroscopy. Under the optimum condition,95% of Ni,98% of Cu,and 88% of Co were recovered. In addition,the removal of iron was studied in the water leaching stage. The results demonstrate that this process provides an effective approach for extracting multiple metals from complex concentrates or ores.

Nitrate Leaching in an Irrigated Wheat-Maize Rotation Field in the North China Plain

Soil water deep drainage and nitrate (NO-3) leaching losses below the root zone were investigated in a 1 ha wheatmaize rotation field under traditional agricultural management that local farmers generally follow in the North China Plain, using the soil water balance method and NO3-N concentration in suction samples. Water drainage, and NO3-N distribution and leaching losses exhibited pronounced spatial and temporal variability. Soil water deep drainage and NO3N leaching loss mostly occurred during the summer maize growing season (rainy season), which coincided with irrigations and significant rainfall. On average, soil water deep drainage was 39 and 90 mm in the 1998/1999 and 1999/2000 cropping years, correspondingly, accounting for 10% and 19% of the total irrigation plus rainfall, respectively. The NO3-N leaching loss from soil and fertilizer N below the root zone ranged from 6 to 17 (averaging 12) and 30 to 84 (averaging 61) kg N ha-1 in 1998/1999 and 1999/2000, correspondingly, equivalent to 1.4%-4.1% and 7.3%-20.3% of N fertilizer applied,respectively. The results indicated that water and fertilizer inputs could be greatly reduced, thus improving water and nutrient use efficiency in this region.

Zinc extraction from zinc oxidized ore using(NH4)2SO4 roasting−leaching process

An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,roasting temperature,and holding time on zinc extraction.The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol^−1.The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry–differential thermal analysis curves.The water leaching conditions,including the leaching temperature,leaching time,stirring velocity,and liquid-to-solid ratio,were discussed,and the leaching kinetics was studied.The reaction rate was obtained under outer diffusion without product layer control;the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol^−1.The maximum zinc extraction ratio reached 96%while the efficiency of iron extraction was approximately 32%under appropriate conditions.This work offers an effective method for the comprehensive use of zinc oxidized ores.

COD_(Cr) leaching rules of municipal solid waste in Songtao Reservoir,Hainan Province,China

By the means of static leaching experiment and dynamic leaching experiment,CODCr leaching rules of dumped MSW(Municipal Solid Waste) in Songtao Reservoir,Hainan Province,China,were studied. And according to academic experience and fitted results of experiment data,the models of CODCr leaching rules in the leaching condition were deduced. The static leaching experiment indicates that,both in water-changing section and no-water-changing section,the ratio of liquid to solid has a remarkable influence on CODCr leaching concentration. The exponential model could be established to approximately describe CODCr leaching rules and the curve fits well. The dynamic leaching experiment indicates that,leaching rules of MSW can be approximately described by power model,which can well fit the leaching experiment data. By the contrast of the static leaching experiment and dynamic leaching experiment,the differences of CODCr leaching rules between the two experiments are significant. By the exponential model,the average static leaching rate of CODCr is calculated as 882.24 mg/(kg·d) for water-changing section and 320.39 mg/(kg·d) for no-water-changing section; by the power model,the average dynamic leaching rate of CODCr is 208.77 mg/(kg·d).

A LEACH-Head Expected Frequency Appraisal Algorithm for Water-Environment Monitoring Networks

Water-environment monitoring network (WMN) is a wireless sensor network based real-time system, which collects, transmits, analyzes and processes water-environment parameters in large area. Both cluster selection mechanisms and energy saving strategies play an important role on designing network routing protocols for the WMN. Since those existing routing algorithms can not be used directly in the WMN, we thus propose an improved version of LEACH, a LEACH-Head Expected Frequency Appraisal (LEACH-HEFA) algorithm, for the WMN in this paper. Simulation results show that the LEACH-HEFA can balance the energy consumption of nodes, rationalize the clustering process and prolong the network lifetime significantly in the WMN. It indicates that the LEACH-HEFA is suitable to the WMN.

硫酸亚铁焙烧-水浸工艺分离黑铜泥中铜和砷

采用硫酸亚铁焙烧-水浸工艺实现黑铜泥中铜、砷一步分离。考察了铁砷摩尔比(Fe/As)、焙烧温度、焙烧时间、水浸初始pH等对试验效果的影响。较优工艺条件为:焙烧温度400℃、Fe/As=0.3、焙烧时间120 min、水浸温度80℃、水浸时间60 min、水浸液固比7 mL/g、水浸初始pH=4.5,沉砷率高达99%以上,铜浸出率高达96%以上。经XRD分析,沉砷渣主要成分为臭葱石和氧化铁,实现了砷的安全固化处置。

矿渣水泥基复合材料在杂散电流作用下的抗软水溶蚀机理研究

在轨道交通工程运营期间,复杂的服役环境导致混凝土结构耐久性下降。本文主要研究了在杂散电流与软水溶蚀耦合作用下,矿渣掺量、水胶比和杂散电流电压强度对矿渣水泥基复合材料微观结构的影响。结合X射线衍射、热重、扫描电子显微镜和压汞等方法,分析了矿渣水泥基复合材料经溶蚀90 d后的物相组成、Ca(OH)_(2)含量、微观形貌以及孔结构变化。研究结果表明:矿渣掺量越大,矿渣水泥基复合材料内部的Ca(OH)_(2)含量越少,材料的孔隙率越低,结构更均匀致密;随着杂散电流电压强度的增加,矿渣水泥基复合材料内部的Ca(OH)_(2)和AFt含量变少,且AFt和Ca(OH)_(2)等物相边界变得模糊不清;矿渣水泥基复合材料中C-(A)-S-H的含量略有增多,孔隙率略有下降;随着水胶比的增大,矿渣水泥基复合材料内部的Ca(OH)_(2)含量变少,剩余物相含量变少,微观结构变得松散多孔,孔径结构整体粗化,孔隙率增大。

滨海黏质盐渍土饱和泥浆与不同土水比土壤浸提液电导率的响应关系分析

为统一和精准判定耐盐作物种植地块的土壤盐渍化程度,并针对饱和泥浆制备时饱和点的不确定性及其电导率测定的不稳定性等问题,本试验采用室内化验与统计分析方法,系统研究饱和泥浆与饱和土壤溶液两者间含水量和电导率的响应关系,以及饱和泥浆电导率、全盐含量与土水比1∶0.5、1∶1、1∶2.5、1∶3.5、1∶5土壤浸提液电导率与全盐含量的响应和换算关系。结果表明:在滨海黏质盐渍土区,利用计算田间土壤孔隙度得到的饱和土壤溶液含水量、电导率不能直接代替饱和泥浆含水量、电导率,尽管二者的响应关系达到极显著水平;饱和泥浆电导率、全盐含量分别与土水比1∶1和1∶0.5土壤浸提液的数值差异最小,且与土水比1∶0.5~1∶5间各处理土壤浸提液的相应指标均呈极显著的响应关系;饱和泥浆电导率与土水比1∶5土壤浸提液的电导率、饱和泥浆全盐含量与土水比1∶1土壤浸提液全盐含量相关性最高,可分别用最佳拟合线性模型进行换算,模型分别为ECe(mS/cm)=5.406EC1∶5-0.284 4,TSe(g/kg)=0.836 4TS1∶1-0.135 9。

垃圾焚烧飞灰水洗脱氯及重金属Zn的浸出特性研究

以生活垃圾焚烧飞灰为原材料,通过单因素实验和响应面优化实验研究了飞灰脱氯的最佳水洗条件以及飞灰中Zn的最佳浸出条件。结果表明,在最佳水洗条件(水洗温度35℃、水洗时间10 min、水洗液固比10 mL/g)下,飞灰氯离子洗脱率为73.4%,二次水洗后,氯离子洗脱率可达96.8%。酸浸实验中,不同种类酸对飞灰中Zn的浸出效果为盐酸>硝酸>单宁酸(TA)>二乙烯三胺五乙酸(DTPA)>乙二胺四乙酸二钠(EDTA)。采用响应面优化法确定飞灰中Zn的最佳盐酸浸出条件为:浸出液固比10 mL/g,盐酸摩尔浓度2.0 mol/L,浸出时间8 h,此时Zn浸出率可达到70.48%。

利用垃圾焚烧渣制备陶瓷透水路面砖的试验研究

垃圾焚烧渣是一种危险的固体废弃物,无害化利用垃圾焚烧渣具有重要意义。以垃圾焚烧渣为主要原料,通过高温烧结工艺制备了一种综合性能较佳的透水砖,研究了垃圾焚烧渣的添加量与烧成温度对样品结构与性能的影响规律。结果表明:添加适量的废玻璃及适当提高烧成温度能够改善试样的强度及环境安全性;当垃圾焚烧渣、废玻璃与煤粉(外加)的添加量分别为60%、40%、20%(质量分数)时,在1 200℃下烧成制品的透水系数、抗折强度与抗压强度分别为0.58 mm/s、6.23 MPa和18.58 MPa,其强度和透水系数分别达到了R_(f)4.5与B等级,且制品的Cu^(2+)、Pb^(3+)和Zn^(2+)浸出浓度满足GB 5085.3—2007《危险废物鉴别标准浸出毒性鉴别》要求。XRD与SEM-EDS分析结果表明,由废玻璃熔融而成的高温液相溶解了三氧化二铅、氧化锌和氧化铜,抑制了Cu^(2+)、Pb^(3+)和Zn^(2+)的浸出。提高烧成温度能够降低样品的气孔率,促进三氧化二铅、氧化锌与氧化铜的溶解,进而协同改善制品的环境安全性。莫来石与玻璃相相互胶结,连通气孔均匀分布,赋予了透水砖较高的强度与优良的透水性能。

基于亚临界技术的铬革屑水解工艺研究

通过单因素实验和正交试验优化,亚临界水解铬革屑最优工艺为:温度150℃、液比25、反应时间75 min、CaO用量6%。铬革屑水解率为(83.98±0.16)%。水解过程无废液产生,水解产物主要为多肽、短肽和少量氨基酸。水解产物的铬含量为(34.81±2.29)mg/kg,符合农业部有机肥铬含量标准,具有作为有机肥的应用前景。铬革屑水解产生的铬绝大部分沉积在铬渣中。铬渣浸出液的铬和六价铬含量分别为14.285 mg/L和1.544 mg/L,低于国家标准《危险废物鉴别标准浸出毒性鉴别》的限值,实现了铬革屑无害化处理。

基于作物水分亏缺指数和盐分淋洗系数的新疆棉田节水控盐优化方法

通过灌溉对作物根区土壤水盐环境进行适时适度的调控是促进新疆绿洲农业可持续健康发展的重要举措,其中最为关键的一环当属灌溉制度尤其是灌水定额的优化。为了提高灌水控盐效率,该研究以新疆沙湾市膜下滴灌盐碱棉田为研究对象,以当地传统灌溉制度为对照,在基于作物水分亏缺指数(plant water deficit index,PWDI)评估并实施智能灌溉的基础上开展了2 a(2021与2022)田间灌水控盐试验,通过设置不同的盐分淋洗系数(2021年:1.0与2.0;2022年:1.0、1.4、1.8、2.2与2.6)探讨灌水定额对土壤水盐运移与棉花生长以及水分吸收利用的影响。结果表明,在固定PWDI阈值(评估值超过阈值时开启灌水)的情况下,在一定范围内随着盐分淋洗系数的增大,灌水定额增加,灌水周期延长,灌水总量增大,更多盐分被被淋洗到根区下部甚至根区以下,从而改善根域水盐环境,减轻水盐胁迫,促进棉花生长并增产,但灌溉水利用效率呈缓慢下降趋势。然而,当盐分淋洗系数(灌水定额)增大到一定程度时,长期优越的根域水盐环境导致棉花徒长,即营养生长旺盛而生殖生长迟滞,灌水周期缩短,灌水总量急剧上升,产量不再增加反而有下降趋势,灌溉水利用效率显著降低。综合考虑盐分淋洗、棉花生长与产量以及水分利用效率,当试验区PWDI阈值取为0.5时建议对应的盐分淋洗系数取为2.2。该研究可为新疆盐碱棉田高效生产以及绿洲农业可持续健康发展提供理论依据与技术支撑。

辉钼精矿氧压水浸工艺及动力学研究

采用正交试验确定辉钼精矿氧压水浸的最佳工艺条件,并在最佳工艺条件下进行氧压水浸过程MoS_(2)氧化分解反应的动力学研究。结果表明:最佳工艺条件为矿石粒度D_(90)=46μm、氧压1.1 MPa、温度230℃、液固比7∶1和反应时间1 h;在此条件下,钼转化率最高可达99.77%,铜浸出率为97.56%,铁浸出率为88.71%。在170~230℃浸出温度范围内(其他工艺条件均为上述最佳值),辉钼精矿中MoS_(2)氧化分解反应遵循未反应核收缩模型,该过程主要受化学反应控制,表观活化能为45.71 kJ/mol。