Modeling Date Palm Trunk Fibers (DPTF) Packed Bed Adsorption Performances for Cadmium Removal from Aqueous Wastewater

In this study,the potential of a low-cost bio-adsorbent,taken directly from Date Palm Trunk Fibers(DPTF)agricultural wastes,for cadmium ions removal from wastewaters is examined.The performances of this adsorbent are evaluated by building breakthrough curves at different bed heights and flow rates while keeping other parameters,such as the initial feed concentration,pH,and particle size,constant.The results indicate that the maximum cadmium adsorption capacity of DTPF can be obtained from the Thomas model as 51.5 mg/g with the most extended mass transfer zone of 83 min at the lowest flow rate at 5 ml/min.The saturation concentrations(NO)and the rate constant(kab)obtained from the BDST(bed depth service time)model are 7022.16 mg/l and 0.0536 l/mg.min,respectively.Using the Yon-Nelsen Model,it is found that operating at a lower flow rate leads to a larger value of the elapsed needed time to reach a 50%breakthrough.The Wolborska model indicates that the bed capacity increases with decreasing the flow rate,and the adsorbent can achieve a greater external mass transfer kinetic coefficient(2.271/min)at a higher flow rate.

Assessment of Cadmium and Lead in Dried Sewage Sludge from Lubigi Feacal Sludge and Wastewater Treatment Plant in Uganda

Sludge contains organic and inorganic compounds including traces of heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), chromium (Cr) and others. These metals restrict the use of sludge in agriculture because their accumulation is harmful to the environment and particularly the food chain. Cadmium and lead are among the most common heavy metals found in municipal wastewater treatment plant sludge. They are capable of bioaccumulation in plant tissues like roots and leaves and are non-biodegradable and therefore they remain in the sludge which is disposed on land or used as fertilizers on farms. The presence of heavy metal pollutants serves as a great threat to soils and also makes plants grown on such soils unfit for animal and human consumption as they may have detrimental effects to animal and human life. For instance, Pb and Cd are known to be human carcinogens. This study therefore aimed to investigate the levels of Cd and Pb in the treated dry sludge from Lubigi Feacal Sludge and Wastewater treatment plant located in Kawempe division, Kampala city, Uganda so as to ascertain its safety for use on agricultural lands. Two batches of samples were collected and analyzed at Government Analytical laboratory in Wandegeya, Uganda. The acid digested sludge samples were analyzed using Atomic Absorption Spectroscopy (AAS) method. The average concentrations of Pb found in collected sludge samples, batch 1 (11.912 mg/kg dm) and batch 2 (5.304 mg/kg dm) were far below the Environment Protection Agency (EPA) maximum permissible concentration (840 mg/kg) for any land application. Cadmium was not detected in all the sludge samples collected;there is an implication that it is either completely absent in the sludge generated by the plant or present but far below detectable levels. The sludge generated from Lubigi fecal sludge and wastewater treatment plant is therefore safe for application on agricultural lands as far as Pb and Cd concentrations are concerned.

Removing cadmium from electroplating wastewater by waste saccharomyces cerevisiae

The appropriate condition and scheme of removing cadmium from electroplating wastewater were investigated by adsorption-precipitation method using waste saccharomyces cerevisiae(WSC) as sorbent. Effect factors on biosorption of cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae and precipitation process of waste saccharomyces cerevisiae after adsorbing cadmium were studied. The results show that removal rate of cadmium is over 88% after 30 min adsorbing under the condition of cadmium concentration 26 mg/L, the dosage of waste saccharomyces cerevisiae 16.25 g/L, temperature 18 ℃, pH 6.0 and precipitation time 4 h. Biosorption-precipitation method is effective to remove cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae. The SEM, infrared spectroscopy and Zeta-potential of the cells show that chemical chelating is the main adsorption form; electrostatic attraction, hydrogen bonding and van der Waals force all function in adsorption process; and ―NH2―,―C=O―,―C=O―NH―,―CH3, ―OH are the main adsorption groups.

Study on Cadmium Resistant-Bacteria Isolated from Hospital Wastewaters

In hospital, a variety of substances are in use for medical purposes as diagnostics and researches. Among them, heavy metals which are not biodegradable by chemical reactions have bioaccumulation properties. Cadmium is a toxic pollutant that enters hospital wastewaters by different ways. However, isolated bacteria from hospital effluents have high resistance to antimicrobial agents and therefore the ability to uptake cadmium and other metals. So, their use is recommended for wastewater bioremediation. In this study, twelve cadmium-resistant bacteria were isolated from hospital wastewaters and identified. The cadmium-resistant isolates characterized include both Gram-negative [75%] and Gram-positive [25%]. The Minimum Inhibitory Concentration of hospital wastewaters isolates was determined in solid media and was ranged from 250 to 950 micrograms/milliliters. All the isolates showed co-resistance to zinc and mercury. They were also antibiotic resistant and tolerated up a significant concentration of NaCl. The cadmium-resistant species Klebsiella pneumoniae and Pseudomonas aeruginosa were the most resistant to cadmium. The species Klebsiella pneumonia also resists to the highest concentrations of zinc and mercury. The results of toxicity tests on Vibrio fischeri, showed that the DI50 [15 min] as low as 0.07 carried away 50% luminescence inhibition.

Removal of Some Toxic Ions from Seawater and Wastewater by Sorption onto Natural, Synthetic Hydroxyapatite and Alginate-Hydroxyapatite Composite Nanoparticles: A Comparative Study

The main objective of this paper is to study the removal of Cadmium(II), Lead(II), Chromium(VI), and Mercury(II) ions by sorption onto different natural and synthetic nanoparticles. Special attention has been given to the application of fish bone in nanoform as a useful, inexpensive and eco-friendly alternative material. A comparison between natural hydroxyapatite (fish bone), synthetic hydroxyapatite nanoparticles (HAP) and alginate-hydroxyapatite composite (Alg/Hap) to assess their removal efficiencies to remediate the selected heavy metals has been done. Surface characterization by using different techniques has also been performed to understand the influence of surface characteristics of the adsorbent materials in the removal process. Different parameters (pH, contact time, mass dose and metal ion concentration) have been examined to identify the optimum conditions for remediation of different metals from polluted water. The potential applications of the biosorbents for removal and sorption of these metal ions from seawater and wastewater samples were also investigated and evaluated.

Synthesis of Modified Walnut Shell Biochar and Its Performance of Cadmium Adsorption

Biochar is a functional and environmentally friendly material mainly made from by-products of industrial and agricultural production as raw material, which is cracked at high temperatures and slow speeds. The preparation of biochar requires the thermochemical conversion of biomass in an oxygen-restricted environment. Different raw materials and preparation processes result in biochar with different internal structures and biofunctional groups, which often have different properties. Adsorption of heavy metal pollutants is one of the main research directions for biochar application, and there are still areas that can be improved in the current research for biochar for treating heavy metal wastewater. In this study, we take the treatment of cadmium-containing wastewater as an example, walnut shell biochar (WSBC) as a carrier, iron(VI) compounds as a modifying reagent, and test the performance of cadmium-containing wastewater treatment using simulated cadmium-containing wastewater by adjusting the pyrolysis process and modification method at the same time to find the optimal experimental scheme, and give a reasonable theoretical explanation in relation to the results of the characterization tests, such as SEM, FT-IR, and so on. The characterized results show that iron(VI) compound (K2FeO4)-modified WSBC has a significant ability to remove cadmium contamination in the wastewater (remove 96.62% of cadmium in 1 minute), and its structure is different from other iron compound-modified ones. The aim of this study is to improve the efficiency of cadmium adsorption by specific types of biochar, while realizing the whole process as environmentally friendly as possible.

镉离子对养殖废水生物脱氮性能及功能基因的影响

选取了养殖废水中的重金属污染物镉离子为研究对象,为揭示其对生物脱氮系统的影响。检测氮转化功能基因丰度,确定功能基因与理化参数相关性并分析镉离子胁迫下生物脱氮的驱动因素。实验结果表明,镉离子显著抑制生物脱氮性能,硝化过程对于镉离子的敏感性相比于氨氧化过程更强。细菌16S rRNA和氮转化功能基因的丰度随镉离子浓度的升高而显著降低,其中出水氨氮、好氧末端硝酸盐氮浓度都与功能基因呈较强的相关性。此外,硝化和氨氧化水平、NO_(2)^(-)-N的氧化能力、完全反硝化水平是生物脱氮性能的关键驱动因素,分别对氨氮去除率、亚硝酸盐氮积累率、反硝化阶段硝酸盐氮去除率有显著影响。本研究从分子生物学角度揭示镉离子对于生物脱氮的影响,为金属离子对于生物脱氮系统的影响研究提供了理论依据。

某石煤矿含镉酸性废水处理站改造工程实例

由于环保政策的影响,益阳地区许多小型煤矿已经关闭,但它们矿区周围仍有渗漏的水需要持续处理。本项目在早期阶段由于雨水和含镉废水分流不彻底,处理规模与实际的废水排放量存在较大差异,处理流程不尽完善,废水水质的监测和自动控制相对不足,出水水质稳定性存在问题。此外,污泥处理技术相对落后,实际处理能力不足。针对上述问题,我们对雨水和污水处理分流进行了优化,增加了调节池,采用了新型含镉酸性废水一体化处理设备,选择了更经济的药剂,提升了控制系统的自动化水平,并对污泥处理系统进行了改进,实现运行效果的提升及运行成本的降低。

硫酸盐还原活性污泥矿化固定酸性矿山废水中的镉

为了实现硫酸盐生物还原法处理酸性矿山废水(AMD)中镉(Cd)的稳定去除,受自然界硫酸盐还原菌诱导的生物矿化现象启发,以驯化的硫酸盐还原活性污泥为种泥,在上流式厌氧反应器内,通过维持进水浓度比COD/SO_(4)^(2-)=2∶1、水力停留时间(HRT)=72h实现了AMD中Cd的稳定矿化,其固化率为100%,且连续36d未见Cd^(2+)的溶出;污泥特性分析表明,硫酸盐还原产生的S2−将废水中的Cd^(2+)转移至污泥中,污泥中的Cd则逐步从不稳定态(可交换态、碳酸盐结合态、铁锰氧化态、硫化物结合态)向稳定态(残渣态)转化,并在污泥表面形成大量离群的微米级镉硫矿;微生物群落结构分析表明,反应器中Desulfovibrio、Desulfuromonas、Acinetobacter、Delftia等丰度明显增加,推测协同代谢实现了Cd的稳定矿化。由此表明,硫酸盐还原活性污泥可通过矿化实现AMD中Cd的稳定去除,为AMD的高效处理及资源回收提供了新思路。

复合生物炭对含镉模拟废水中Cd^(2+)的吸附性能研究

为解决水体中镉离子污染以及固废基材料资源化利用的问题,以小麦秸秆与硼泥等量混合在700℃(氮气驱氧)下煅烧2 h,制备复合生物炭吸附材料(BBm);以BBm为吸附剂,对Cd^(2+)浓度200 mg/L的含镉模拟废水进行Cd^(2+)吸附研究。单因素试验结果表明,随着BBm用量、溶液pH、转速以及吸附反应时间的增加,BBm对Cd^(2+)去除率升高,直至吸附平衡后,去除率稳定;正交试验结果表明,各因素影响由强到弱依次为溶液初始pH值、BBm用量、振荡转速、反应时间,在室温(约25℃)、BBm用量为0.5 g、pH值为8、转速为200 r/min的条件下,对100 mL模拟废水(含镉200 mg/L)吸附180 min,获得去除率99.99%的良好指标;吸附等温拟合结果表明,BBm对Cd^(2+)的吸附过程符合Langmuir等温吸附模型,准二级动力学模型能更好地拟合该吸附过程。

重金属吸附剂巯基丙酰化小麦秸秆的制备与表征

该文以小麦秸秆(WS)、氢氧化钠(NaOH)、L-半胱氨酸(L-Cys)、碳二亚胺盐酸盐(EDC·HCl)、N-羟基琥珀酰亚胺(NHS)为原料,通过化学预处理、酰化反应在WS中引入巯基官能团,制备出重金属吸附剂巯基丙酰化小麦秸秆(MPWS)。通过吸附实验考察了MPWS对水中Cd(Ⅱ)的去除性能,采用单因素实验法确定了MPWS的制备条件,借助红外分析(FTIR)、扫描电镜及能谱分析(SEM-EDS)等表征手段探讨了MPWS的制备机理和吸附机理。结果表明,在WS粒径为0.60 mm,化学预处理NaOH溶液浓度为0.1 mol/L,n(EDC·HCl)∶n(L-Cys)为0.05∶1,m(NHS)∶m(EDC·HCl)为1∶1,m(CWS)∶m(L-Cys)为1∶5,反应介质pH值为10,反应温度为35℃,反应时间为3 h的制备条件下,MPWS对水中Cd(Ⅱ)的吸附性能最好,Cd(Ⅱ)的最高去除率可达94.20%。FTIR和SEM-EDS分析表明,NaOH溶液预处理除去了一定量的半纤维素、木质素,MPWS中成功引入了巯基、胺基、羧基,Cd(Ⅱ)被吸附到MPWS结构中;MPWS对Cd(Ⅱ)的吸附机理主要包括配位作用、离子交换作用、静电吸附作用和物理吸附作用。

工业废水中重金属离子的处理技术研究

由于当代社会的快速发展,环境污染尤其是水污染问题,变得越来越突出。众所周知,重金属的危害十分严重,对人生命健康构成了极大的威胁,因此,找到一种或几种高效的污水处理方法显得尤为重要。与其他污水处理方法相比,物理吸附法因其操作简易、高效、选择性好、成本低廉而应用最为广泛。分子筛材料有着均匀的孔径、高比表面积、高水热稳定性以及可再生的特性,现阶段已然成为处理重金属污水的热门吸附剂。因此本文着重研究工业废水中重金属离子的处理技术研究,为重金属离子降解提供一种可行性方法。

果胶稳定无定形碳酸钙用于模拟含镉废水研究

通过添加果胶作为晶型调控剂,合成果胶稳定的无定形碳酸钙(P-ACC)。利用XRD、SEM、BET吸附法、FTIR及XPS等方法对P-ACC的结构及表面性质进行了分析表征,研究了P-ACC材料对Cd^(2+)的吸附行为,考察了溶液的pH、吸附时间、吸附温度、投加剂量、Cd^(2+)初始浓度等因素对材料吸附性能的影响,探讨了吸附过程的吸附等温线、吸附动力学、吸附热力学行为。结果表明,所合成的P-ACC对Cd^(2+)的最大吸附容量为495.40 mg·g^(-1),吸附过程符合Langmuir吸附等温式和准二级动力学模型;吸附热力学分析表明,吸附是一个自发吸热的过程,所制备的P-ACC对Cd^(2+)具有良好的吸附性能,能在2 h内将初始浓度为2.0 mg·L^(-1)的Cd^(2+)完全去除,为水体中重金属镉污染废水的环境修复提供一个新的研究思路。

氢氧化镁处理含镉废水的研究

以氢氧化镁作为吸附剂处理含镉酸性废水 .结果表明 ,氢氧化镁对Cd2 +的吸附为化学吸附 ,去除率一般可达 98%以上 .氢氧化镁回收后 ,经轻烧处理变成氧化镁 ,仍可以处理含镉废水 。

含氰废水处理方法

综述了含氰废水及其处理方法。重点介绍了处理含氰废水方法—氧化法、酸化回收法、化学沉降法和微生物降解法、自然降解法、碱氯氧化法、双氧水氧化法、高温水解法、电解法、二氧化碳—空气氧化法及纳米二氧化钛光催化氧化法的基本原理。

镉在不同土壤和蔬菜中残留规律研究

研究了镉在不同类型土壤和蔬菜中的残留积累规律.结果表明,含镉污水灌溉是造成农田土壤镉污染主要原因之一.土壤中镉残留量随污水镉浓度增加而增高.土壤镉含量与蔬菜中镉含量呈显著正相关.供试土壤及蔬菜可食部分镉的累积顺序为:粘土>壤土;壤土蔬菜>粘土蔬菜,小白菜(叶)>萝卜(根)>莴苣(茎)>辣椒(果)>豇豆(豆).

脉冲电絮凝处理含镉重金属废水

采用脉冲电絮凝方法处理含镉重金属废水,考察了通电时间、pH值、离子强度、电流密度及占空比等因素对溶液中Cd2+去除效果的影响,并结合相应的计算公式核算了相应的电耗和铝板消耗。实验结果表明,在通电时间为60 min,电流密度为10 mA/cm2,电导率为7.8 ms/cm,占空比2.5,pH值7.82的条件下,Cd2+去除率达到了99.86%,电耗和铝板消耗分别为0.832 kWh/m3和100.7 g/m3。

生物吸附-沉降法去除电镀废水中镉

以水洗废啤酒酵母为吸附剂,采用吸附-沉降法,研究水洗废啤酒酵母对电镀废水中镉的吸附规律及沉降效果。结果表明,在废水中镉含量为26mg/L、pH7、水洗废啤酒酵母用量40g/L(含水约72%)、室温(约18℃)、搅拌速度800r/min、吸附时间30min、沉降3.5h的条件下,废水中镉的吸附率及吸附-沉降后镉的去除率均达96%以上。并采用透射电子显微镜、电动电位及红外光谱分析手段,分析水洗废啤酒酵母对镉的吸附机理。水洗废啤酒酵母对镉的吸附不仅发生菌体表面,也发生在菌体内部。吸附过程存在化学络合、静电吸引、氢键等作用。

ClO_2对医院高浓度含氰废水处理的试验研究

以医院排放的高浓度含氰废水为研究对象 ,采用“硫酸亚铁 +曝气”初级化学处理和ClO2 二级深度氧化处理相结合的处理模式 ,不仅使含氰废水实现无毒化处理 ,而且使高浓度含氰废水实现资源化回收利用。试验表明 ,处理后的废水中CN-浓度达到国家排放标准GB8978 1996中的一级标准 ,为医院高浓度含氰废水的治理提供了一种新的方法。

啤酒酵母吸附镉离子的试验研究

研究了啤酒酵母对镉的生物吸附过程 ,结果表明 ,啤酒酵母吸附镉的速度是非常快的 ;p H对镉的吸附影响较大 ,吸附较佳的 p H范围为 4～ 8,并且啤酒酵母有调节 p H的作用 ,p H为 4～ 8的溶液在吸附反应后 ,其 p H接近于 5 .8;温度、酵母用量、Cd2 +的初始浓度对吸附均有一定的影响。实际含镉废水处理结果表明 ,啤酒酵母处理含镉废水是有效的。