Modified polyacrylamide hydrogels and their application in removal of heavy metal ions

Modified crosslinked polyacrylamides having different functional groups were prepared by Mannich reaction using different amine compounds such as ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA) and sulfomethylation reaction. Products were characterized by determination of their basic group content (BGC), hydroxymethyl group content (HMG), equilibrium degree of swelling (EDS) and FT-IR spectra. For Mannich reactions, BGC and EDS changed with amount of employed amine compounds, reaction time and temperature. Sulfomethylation reactions gave products with high BGC and very high EDS. FT-IR spectroscopic analysis confirmed that a parallel hydrolysis reaction occurred along with the expected modification reactions. The products were used for removal of Cu(II), Cd(II) and Pb(II) ion under competitive and non-competitive conditions at different pH. The metal ion removal capacities changed depending their BGC and EDS. While the Mannich products were selective towards Cu(II) ion, the sulfomethylation products were highly selective to Pb(II) ions. The polymers were used several times by regeneration without loss of adsorption capacity and changing of selectivity properties.     

Effects of phosphorus-rich sawdust biochar sorption on heavy metals

ABSTRACT

The aim of this paper is to study the efficiency of typical heavy metals in electroplating sludge in terms of different phosphorus dosages (0.5 wt.%, 1 wt.% and 3 wt.%), initial pH (2, 3, 4, 5 and 6) and adsorption times (1, 3, 5, 7 and 12 h) of biochar. The heavy metal speciation was determined after adsorption to estimate the stability of ion-adsorption precipitation. Results show that phosphorus-modified biochar enhances the removal efficiency of heavy metals. Low mobility of heavy metal speciation was investigated. It is also shown that initial pH has a significant impact on the heavy metal speciation after adsorption.     

生物炭吸附重金属离子的研究进展

生物炭在过去的十几年里受到了广泛关注,由于其低成本、环境友好、可再生等优点,在环境管理方面具有良好的应用前景。本文介绍了生物炭的概念、应用和性质,重点综述了生物炭吸附重金属离子的研究进展,并探讨了目前面临的挑战和应用前景。生物炭是在缺氧或无氧条件下热化学转化生物质得到多孔富碳材料,主要用于土壤改良,可以提高作物产量、实现碳封存以及减少温室气体排放,并且在催化、能源和水处理等方面具有潜在的应用。生物炭制备方法包括热解、气化、水热炭化等,生物炭的性质受生物质原料、制备工艺和技术参数影响。重点介绍了生物炭吸附重金属离子的相关研究,包括生物炭吸附重金属离子的影响因素、吸附机理和改性生物炭的制备。通过吸附动力学、吸附等温线、吸附热力学和表征技术可以揭示表面络合、静电引力、表面沉淀和离子交换等吸附机理。生物炭吸附重金属离子的最新研究主要致力于通过改性提高生物炭的吸附性能,改性方法主要包括物理化学活化以及复合金属氧化物或化合物、功能有机物、纳米粒子等。生物炭吸附重金属离子面临一些问题和挑战,距离实际废水处理应用还有一定差距。     

改性膨润土吸附重金属离子的研究与应用进展

膨润土具有很强的吸附能力,通过对膨润土进行改性,可提高其对重金属离子的去除能力.国内外学者对改性膨润土用于含重金属离子污水的处理进行了广泛的研究.概述了膨润土改性制备方法和表征手段,讨论了影响改性膨润土吸附重金属离子的主要因素.对近年来国内外改性膨润土吸附水体中铬、镉、汞、铅、镍等重金属离子的应用研究进行了综述,并指出了改性膨润土用于重金属废水处理存在的问题和今后的研究方向.     

Competitive adsorption of heavy metal ions (Pb2+, Cu2+, and Ni2+) onto date seed biochar: batch and fixed bed experiments

In a multicomponent systems, the adsorption of Pb²⁺, Cu²⁺, and Ni²⁺ by date seed biochar exhibited competitive behavior. Compared to single component systems, the adsorption capacities of each ion were reduced by 48–75% in both batch and column experiments. Surface complexation with carboxyl and hydroxyl functional groups played a major role in the removal mechanism. Ion exchange mechanism accounted for 37–40% of the total adsorption compared to 57–72% in single component systems. Modified Langmuir isotherm best described the systems. Adsorption capacities and selectivity follow the order: Pb²⁺> Cu²⁺> Ni²⁺. Multi-stage sequences system is recommended to avoid premature exhaustion of biochar.     

分子筛对重金属废水吸附性能的实验研究

为验证分子筛对重金属废水的处理效果,以实际含锰废水为研究对象,采用13X分子筛,通过实验研究了吸附材料用量、吸附时间、搅拌转速和溶液pH对Ca²⁺、Mn²⁺、Mg²⁺吸附效果的影响。结果表明：吸附材料用量增加对Mn²⁺、Mg²⁺的吸附影响较大;随着吸附时间增长,各金属离子去除率增加;适当的转速有利于金属离子的吸附,但各金属离子对应的最佳转速各不相同;pH提高,能够促进分子筛对金属离子的吸附。13X分子筛对金属离子的吸附机理为离子交换吸附和表面吸附。研究表明,13X分子筛在处理低浓度含锰重金属废水方面表现出良好的应用前景。     

高岭土高温吸附重金属和碱金属的研究进展

高岭土在高温下对碱金属和重金属具有吸附能力,可以解决煤、生物质和垃圾等在燃烧、气化等过程中产生的结渣、积灰、腐蚀以及重金属和超细颗粒物排放等问题。国内外学者已对此进行了长期研究,但仍存在相关的难度和问题,因此本文从高岭土高温结构特征、研究方法、高温吸附机理、高温吸附技术应用效果以及高岭土改性等5个方面介绍了相关重要成果,并结合前人研究成果和作者自身的研究经验,提出了本领域研究的展望。指出缺乏简便而准确的金属蒸气定量发生装置和在线检测装置严重阻碍了高岭土高温吸附的试验研究,亟待开发出对应的新方法或新设备;高岭土高温吸附的同时其结构因为高温也在发生畸变,掌握其中的关联是理解高温吸附行为的关键之一;烟气组分对吸附的影响研究仍不充分,因此目前无法形成复杂烟气组分下的高岭土高温吸附行为规律和数学描述;技术应用过程中,高岭土添加量较大（通常大于3%）,可能对燃烧或气化工艺产生不良影响,抑制了其工业应用;高岭土改性是提升吸附效率、降低高岭土用量的有效方法,改性工艺仍有待深入研究,但因为吸附后高岭土难以分离回收和循环再生,改性成本必须低。     

Preparation of amidoximated polyester fiber and competitive adsorption of some heavy metal ions from aqueous solution onto this fiber

In this study, a fibrous adsorbent containing amidoxime groups was prepared by graft copolymerization of acrylonitrile (AN) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (Bz₂O₂) as initiator in aqueous solution, and subsequent chemical modification of cyano groups by reaction with hydroxylamine hydrochloride in methanol. The grafted and modified fibers were characterized by FTIR, TGA, SEM, and XRD analysis. The crystallinity increased, but thermal stability decreased with grafting and amidoximation. The removal of Cu(II), Ni(II), Co(II), Pb(II), and Cd(II) ions from aqueous solution onto chelating fibers were studied using batch adsorption method. These properties were investigated under competitive conditions. The effects of the pH, contact time, and initial ion concentration on the removal percentage of ions were studied. The results show that the adsorption rate of metal ions followed the given order Co(II) > Pb(II) > Cd(II) > Ni(II) > Cu(II). The percentage removal of ions increased with initial ion concentration, shaking time, and pH of the medium. Total metal ion removal capacity was 49.75 mg/g fiber on amidoximated fiber. It was observed that amidoximated fibers can be regenerated by acid without losing their activity, and it is more selective for Pb(II) ions in the mixed solution of Pb‐Cu‐Ni–Co‐Cd at pH 4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

污泥生物炭制备及其对磷的吸附性能研究

以污水污泥、粉煤灰为原料,以质量分数为30%的氯化锌溶液为活化剂,在不同温度下煅烧制备污泥生物炭,用于处理含磷废水。通过单因素静态吸附实验探讨了污泥生物炭对磷的去除效果,并探究了其吸附机理。结果表明：300 ℃制备的污泥生物炭具有较好的除磷效果;扫描电镜（SEM）、比表面分析仪、傅里叶红外光谱仪（FT-IR）对原料和污泥生物炭表征结果显示,污泥生物炭煅烧前后的形貌及表面基团发生了显著改变,煅烧后样品的表面产生了较多微小空隙,比表面积增大,最高可达5.51 m²/g;在磷初始质量浓度为50 mg/L、吸附剂用量为16 g/L条件下,吸附在90 min达到平衡,磷的去除率高达93.73%;吸附过程符合准二级动力学方程及Freundlich等温吸附模型,最大饱和吸附量为9.615 mg/g;整个吸附过程ΔG⁰<0、ΔH⁰<0,是自发进行的放热过程;吸附过程除物理吸附外,同时涉及磷酸盐与吸附剂—OH或C—O共价键发生电子对配位作用,为物理-化学复合吸附;吸附剂第5次吸附为首次吸附量的85.74%,表现出较好的再生性能。     

水凝胶吸附法去除水中重金属离子研究综述

水凝胶是一种具有三维网络结构的高分子材料,因其具有吸附性能强、环境友好、可具备特定功能等诸多优点而倍受环保研究人员的青睐。近年来水凝胶作为一种新型重金属吸附材料在水处理领域中得到了特别的重视,并取得了显著进展。对壳聚糖类、丙烯酰胺类、天然高分子接枝类三类代表性水凝胶的制备及吸附处理重金属废水的研究成果进行了较系统的梳理和总结,并对目前国内外的研究进展进行了分析和讨论,进一步指出了今后的研究重点和方向。     

壳聚糖及其衍生物对重金属吸附性能的研究

壳聚糖分子中含有大量的氨基和羟基,可以进行多种化学改性,得到相应的衍生物。改性前后的壳聚糖对重金属都具有吸附作用,可以作为重金属离子的富集剂。文章综述了近年来壳聚糖及其衍生物在吸附重金属方面的研究进展,对比了不同产品对重金属的吸附容量和选择性,以及它们所适用的条件。文章指出,进一步开发水溶性和螯合能力优良的壳聚糖衍生物是今后研究的方向。     

Smectite organofunctionalized with thiol groups for adsorption of heavy metal ions

The structural characteristics as well as the binding capacity of the functionalized bentonite from Campina Grande (PB), Brazil, were investigated. The sample was modified by acid treatment followed by immobilization of ligands containing thiol (–SH) groups by covalent grafting with surface and interlayer silanol groups. The modification was carried out under anhydrous conditions with (3-mercaptopropyl)trimethoxysilane. The functionalization process changed the hydrophilic nature of the clay mineral into hydrophobic. X-ray diffraction indicated that their original structure had been preserved. The DRIFT spectra demonstrated the presence of organic chains and thiol groups. The BET results indicated decreased porosity and specific surface area after grafting. Organic loading, calculated from TG data was 1.76 mmol g^− 1 of bentonite. The thiol-functionalized bentonite presented binding capacity of Ag⁺ ions about ten times higher compared to the ungrafted sample. These results support a mechanism of adsorption involving primarily ion complexation by the thiol groups (specific) instead of cation exchange (unspecific). The accessibility to the reactive centers was 60–75%. Thus, the adsorption capacity of bentonite can be enhanced by surface modification using organo-functional silane coupling agents. This new hybrid organic–inorganic material may be a good alternative for separation and pre-concentration of heavy metal ions.     

Synthesis of sulfhydryl chitin and its adsorption properties for heavy metal ions

This article discusses the preparation of the water‐insoluble adsorbent sulfhydryl chitin (s‐chitin), by treatment of the chitin with sulfhydryl acetic acid in the presence of sulfuric acid as a catalyst. Its structure was confirmed by elemental analysis, FTIR spectra analysis and near‐IR spectra analysis. We also investigated the adsorption properties of sulfhydryl chitin for Cu^II, Cd^II, Pb^II, Cr^III, and Ni^II. Based on the research results of adsorption capacity, the effect of pH value on adsorption, adsorption kinetics experiments, and selective adsorption experiments were observed. It has been shown that the s‐chitin has much better adsorption for Pb^II, Cu^II, and Cd^II than chitin itself. The adsorption capacities of s‐chitin for Pb^II, Cu^II, and Cd^II were 108.3, 94.7, and 57.1 mg/g, respectively. It also had good adsorption properties for heavy metal ions. The adsorption capacities were also affected by the acidity of medium. The adsorbed Cu^II, Cd^II, and Pb^II could be eluted by diluted chlorhydric acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 151–155, 2000     

纤维素纳米纤维及其改性产物吸附重金属的研究进展

重金属污染是目前全世界面临的一个重大挑战,传统治理方法成本高、效率低等缺陷已不符合当今社会可持续发展战略。纤维素纳米纤维（cellulose nanofiber,CNF）因可再生、活性高、比表面积大和密度低等优点,在重金属吸附领域显示出巨大的应用潜力。本文主要综述了CNF的化学改性方法及其改性产物在水体系重金属离子吸附中的应用进展。首先对CNF的改性进行了系统的综述,主要包括化学接枝改性（羧基化、氨基化、巯基化、磷酸基化、磺酸基化和醛基化和硅烷化等）与接枝共聚改性。其次从结构设计方面重点阐述了改性CNF以气凝胶、水凝胶和复合膜等不同形态对水体系中重金属离子进行吸附的应用研究。最后,对CNF基重金属吸附剂的优缺点进行了讨论,指出了CNF基重金属吸附剂在局限性和适用性等方面的挑战,展望了CNF在水体系重金属离子去除领域的发展方向。     

The adsorption of PAHs, BTEX, and heavy metals on surfactant-modified desulfurization sorbents in a dry scrubber

The injection of dry Ca-based sorbents for removing acid gases had been investigated previously. However, the utilization of Ca-based sorbents for adsorbing other air pollutants was rarely examined. The objective of this study was to investigate the reduction of organic compounds polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) and heavy metals by using the desulfurization sorbents in a dry scrubber integrated with a fabric filter. Four surfactants, calcium lignosulfonate, sodium lignosulfonate, alkyl naphthalene sodium sulfonate and β-naphthalene sodium sulfonate condensates, were used as additives to modify the surface characteristics of desulfurization sorbent calcium hydroxide (Ca(OH)₂). Modifying the desulfurization sorbents with surfactants showed different effects on removal of PAHs, BTEX, and heavy metals, and exploited the potential of Ca-based sorbents for adsorbing air pollutants other than SO₂.     

Mechanism transformation of cyclohexene-thiophene competitive adsorption in FAU zeolite

Competition of hydrocarbon compounds with sulfides in gasoline has caused a not very high selectivity of sulfides in adsorption desulfurization so far, resulting in a reduction of catalyst lifetime as well as more sulfur oxide emissions. Tostudy the whole competitive process changing with the increase of the loading, the dynamic competition adsorption mechanism of cyclohexene and thiophene in siliceous faujasite (FAU) zeolite was analyzed by the Monte Carlo simulation. The results showed that with the increase of the loading, thiophene and cyclohexene had different performances before and after the inflection point of 40 molecule/UC. The adsorbates weredistributed ideally at optimal sites during the stage that occurredbefore the inflection point, which is called the optimal-displacement adsorption stage. When approachingthe inflection point, the competition became apparent and the displacement appeared accordingly, some thiophene molecules at S sites (refers to the sites inside the supercages) were displaced by cyclohexene. After the inflection point, the concentration of adsorbates at W sites (refers to the 12-membered ring connecting the supercages) was significantly reduced, whereas the adsorbates at S sites got more concentrated. The stage some cyclohexene molecules displaced by thiophene and inserted into the center of the supercage can be named as the insertion-displacement adsorption stage, and both the adsorption behavior and the competitive relationship became localized when the adsorption amount became saturated. This shift in the competitive adsorption mechanism was due to the sharp increase of interaction energy between the adsorbates. Besides, the increase in temperature and ratio of Si/Al will allow the adsorbates, especially thiophene molecules to occupy more adsorption sites, and it is beneficial to improve the desulfurization selectivity.     

Preparation of SiO2/Si3N4 ceramics with step gradient porosity and heavy metal ion adsorption

Microporous ceramics with slag gradient distribution were prepared by interlayer bonding methods, using silicon dioxide and silicon nitride as the main raw materials. The material performances of gradient ceramics and uniform ceramics were discussed, and the adsorption effects of Cd (Ⅱ), Pb (Ⅱ) between them were compared. The experimental results show a flexural strength of gradient ceramics of 10.67 MPa, bonding strength of the bonding layer of 15.28 MPa, and only a 0.89% difference in the line shrinkage of the gradient layer of different slag contents, indicating that it is feasible to utilize interlayer bonding methods to prepare gradient ceramics. The maximum adsorption quantity of Cd (II), Pb (II) of gradient ceramics can reach 3.48 mg/g and 4.40 mg/g, respectively. For an average slag content of 17.5 wt%, gradient ceramics exhibited high permeability flux equivalent to ceramic with 25 wt% slag content and heavy metal adsorption amount equivalent to ceramic with 20 wt% slag content. Overall, the gradient ceramics prepared by interlayer bonding method can effectively improve the removal efficiency of adsorbent and the overall filtration efficiency.     

Synthesis of activated carbons from black sapote seeds,characterization and application in the elimination of heavy metals and textile dyes

Many different techniques may be used to remove industrial pollutants from wastewater. Adsorption using activated carbon has been reported to be an effective method. This work proposes the use of a vegetable residue (black sapote seeds) as a raw material for its synthesis. These carbons were chemically activated using phosphoric acid and carbonized at 673 and 873 K. Adsorption isotherms were constructed for the textile dyes on the carbons, and this data was treated using Langmuir's equation to quantitatively describe the adsorption process. The synthesized carbons were characterized using FTIR, EA, SEM, Nitrogen adsorption (specific surface areas of 879 and 652 m²·g^-1), and their points of zero charge (2.1 and 2.3). It was possible to adsorb both heavy metals and textile dyes present in aqueous solutions and wastewaters using these activated carbons. Heavy metals were adsorbed almost completely by both carbons. Cationic dyes where adsorbed (58-59.8 mg·g^-1) in greater amounts compared to anionic dyes (10-58.8 mg·g^-1). The amount of anionic dyes adsorbed increased almost 30% by changing the pH of the solutions. One of the carbons was thermally regenerated on three occasions without losing its adsorption capacity and it was proved in a flow system.     

Characterization of an alkali activated lagoon ash and its application for heavy metal retention

The wet disposal of ash, from the coal-fired thermal power plants, involves its mixing with water and its impoundment in the ash ponds or lagoons. This causes the interaction of ash and the alkalies present in it with water over a period and the formation of ash zeolites (i.e. zeolitization of the ash) takes place. In order to simulate such ash-water interactions, alkali activation of a typical lagoon ash, from India, has been conducted. Investigations have been conducted to identify the effect of zeolitization of the ash on its physical, chemical and mineralogical characteristics. Such studies are essential to explore the possibility of application of the lagoon ash, and the zeolitized ash, for various environmental applications, viz. retention and removal of heavy metals from the industrial sludge.