Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass

The biosorption of Pb(II), Cd(II), and Co(II), respectively, from aqueous solution on green algae waste biomass was investigated. The green algae waste biomass was obtained from marine green algae after extraction of oil, and was used as low-cost biosorbent. Batch shaking experiments were performed to examine the effects of initial solution pH, contact time and temperature. The equilibrium biosorption data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetics models (pseudo-first order and pseudo-second order). The results indicate that Langmuir model provide best correlation of experimental data, and the pseudo-second order kinetic equation could best describe the biosorption kinetics of considered heavy metals.     

具超强汞富集能力基因工程菌生长情况的研究

对具超强汞富集能力的基因工程菌在重金属汞离子存在的水体中的生长状况进行了研究。实验所采用的基因工程菌由于外源基因的表达而对Hg^2 产生了一定的耐受力,而且这种耐受力经IPTG诱导后还能得到进一步的增强,耐受能力从Hg^2 浓度5mg／L提高到15mg／L。IPTG加入的时机对菌体的生长和耐受力的有效诱导是重要的。一般在OD600为0．5～0．8时加入,且加入后还应保证2h左右的诱导时间。实验结果还表明菌体在生长过程中对碳源的要求很低。     

The biosorption of heavy metals from aqueous solution by Spirogyra and Cladophora filamentous macroalgae

The aim of this research was to develop a low cost adsorbent for wastewater treatment. The prime objective of this study was to search for suitable freshwater filamentous algae that have a high heavy metal ion removal capability. This study evaluated the biosorption capacity from aqueous solutions of the green algae species, Spirogyra and Cladophora, for lead (Pb(II)) and copper (Cu(II)). In comparing the analysis of the Langmuir and Freundlich isotherm models, the adsorption of Pb(II) and Cu(II) by these two types of biosorbents showed a better fit with the Langmuir isotherm model. In the adsorption of heavy metal ions by these two types of biosorbents, chemical and physical adsorption of particle surfaces was perhaps more significant than diffusion and adsorption between particles. Continuous adsorption-desorption experiments discovered that both types of biomass were excellent biosorbents with potential for further development.     

Removal of heavy metals from industrial wastewater using microbial fuel cell

Removal efficiency of gold from a solution of pure tetrachloroaurate ions was investigated using microbial fuel cell (MFC) technology. The effects of type of catholyte solution and initial gold concentration on the removal efficiency were considered. Due to its presence at high levels in the gold wastewater, the effect of copper ions on the removal efficiency of the gold ions was also studied. The effects of pH and initial biomass concentration on the gold removal efficiency was also determined. The results showed that after 5 h contact time, 95% of gold removal efficiency from a wastewater containing 250 ppm of initial gold ions at ambient temperature using 80 g/L yeast concentration was achieved. After 48 h of the cell''s operation under the same condition, 98.86% of AuCl₄ ^– ions were successfully removed from the solution. At initial gold concentration in the waste solution of 250 ppm, pH 2, and initial yeast concentration of 80 g/L, 100% removal efficiency of the gold was achieved. On the other hand, the most suitable condition for copper removal was found at a pH of 5.2, where 53% removal efficiency from the waste solution was accomplished.     

Combination of biosorption and photodegradation to remove methyl orange from aqueous solutions

In this study, metal ion‐modified biomass of waste beer yeast was prepared to improve its adsorption capacity for an anionic dye: methyl orange. The adsorption capacities of Fe³⁺‐, Mg²⁺‐, Ca²⁺,‐ and Na⁺‐modified biomass preparations for methyl orange were 90.8, 51.3, 23.0, and 20.6 mg/g, which were 30, 17, 8, and 7 times that of the unmodified biomass, respectively. Adsorption isotherm experiments showed that the Freundlich model gave better fits than the Langmuir model for methyl orange adsorption on Fe³⁺‐, Mg²⁺‐, Ca²⁺‐modified and unmodified biomass, whereas on Na⁺‐modified biomass the Langmuir model gave better fits. The sorption and desorption kinetics of methyl orange on Fe³⁺‐ and Mg²⁺‐modified biomass both fitted well to the pseudo‐second‐order kinetic models, with R≥0.998, and the desorption processes in NaOH solution (pH 12) were very fast in attaining equilibrium, i.e. within 15 min. In order to avoid secondary pollution, the eluent containing the desorbed methyl orange was treated with a photocatalyst: P25. After that, the eluent could be reused, and thus saving a large volume of eluent.     

矿井废水灌溉对小麦生理特性及重金属积累的影响

以井水灌溉为对照 (CK),采用盆栽试验研究了矿井废水灌溉对小麦生理特性和重金属积累的影响.设置了3个矿区废水灌溉处理:洗煤废水(T₁)、经沉淀处理的洗煤废水 (T₂) 和煤矸石淋溶水 (T₃),于返青期开始进行矿区废水灌溉处理.结果表明： 矿井废水灌溉处理对小麦的生长发育和产量均有不同程度的负面影响.到开花期时,T₁、T₂和T₃处理小麦的单茎质量和叶面积、根系活力和光合速率均显著低于对照(P＜0.05),T₃处理小麦株高和叶绿素含量(SPAD值)显著降低(P＜0.05);T₁、T₂和T₃处理的籽粒产量分别比对照下降15.4%、9.8%和17.8%.此外,矿井废水灌溉处理小麦籽粒中Cr、Pb、Cu和Zn的含量均显著高于对照,表明矿井废水灌溉导致重金属在小麦籽粒中积累.
     

Removal of heavy metals from aqueous solution by common freshwater filamentous algae

Non-living (dried) biomass of five common filamentous algae belonging to Chlorophyta and Cyanophyta (Cyanobacteria) were screened for their metal ion sorption and removal efficiency in a batch system. A considerably higher magnitude of sorption of Pb²⁺ and Cu²⁺ by all the tested algae suggests the prevalence of Pb²⁺- and Cu²⁺-binding ligands in them. The Langmuir isotherm could more appropriately describe metal sorption by the test algae than the Freundlich isotherm. A 1 g l⁻¹ biomass concentration of Pithophora odeogonia and Spirogyra neglecta, respectively removed 97 and 89% Pb²⁺in 30 min from a solution containing 5 mg l⁻¹ initial concentration of Pb²⁺. Metal ion removal by the test algae decreased with increase in metal concentration in the solution. S. neglecta could remove >70% Pb²⁺ even from a solution containing 75 mg Pb²⁺ l⁻¹. S. neglecta and P. oedogonia could remove more than 75% of Pb²⁺ and Cu²⁺ from a multi-metal solution, and therefore have tremendous potential for removing Pb²⁺and Cu²⁺ from wastewaters containing several metal ions simultaneously. Other test algae, namely, Hydrodictyon reticulatum, Cladophora calliceima and Aulosira fertilissima were relatively less efficient in removing metal ions from solution.     

茶废弃物对溶液中重金属的生物吸附研究进展

茶废弃物是农业固体废弃物的一个重要组成部分,来源广泛,数量庞大.由于其具有吸附特性,利用茶废弃物作吸附剂去除废水中的重金属受到了国内外学者的广泛关注.本文从影响因素、吸附机理、吸附剂制备和脱附再生等方面综述了茶废弃物吸附去除溶液中重金属的最新研究进展,认为吸附机理、制备、脱附再生、工艺参数和后处理等是今后实现茶废弃物吸附剂工业化应用的主要研究方向.     

Concentration and annual accumulation values of heavy metals in lake sediments: Their significance in studies of the history of heavy metal pollution

The first part of the paper discusses the significance of using either concentration or accumulation values for expressing the results of investigations of lake sediment cores aimed at studying the history of heavy metal pollution. Neither the values for heavy metal concentration in the lake sediment, whether expressed per gram dry sediment or per gram soluble (organic) sediment, nor the values for their total annual accumulation per unit area of the lake bottom, can, on their own, provide an accurate picture of past pollution conditions, but when considered in combination they render a fairly reliable and detailed interpretation. The second part of the paper deals with Pb, Cd and Hg analyses of cores of varved sediments from several lakes in N. Sweden. Pb and Cd pollution increased during the second half of the 19th century. In most lakes, Hg pollution seems first to have started during the 20th century. Marked increases in both concentration and accumulation of heavy metals took place during the 20th century. For recent decades, the estimated accumulation rates of heavy metals from anthropogenic sources are: Pb 0.5–1.5 µg cm^–2 yr^–1, Cd 15–30 ng cm^–2 yr^–1 and Hg 1–2 ng cm^–2 yr^–1, Higher values were recorded in lakes affected by local emissions.     

Mechanisms of metal resistance in plants: aluminum and heavy metals

Plants have evolved sophisticated mechanisms to deal with toxic levels of metals in the soil. In this paper, an overview of recent progress with regards to understanding fundamental molecular and physiological mechanisms underlying plant resistance to both aluminum (Al) and heavy metals is presented. The discussion of plant Al resistance will focus on recent advances in our understanding of a mechanism based on Al exclusion from the root apex, which is facilitated by Al-activated exudation of organic acid anions. The consideration of heavy metal resistance will focus on research into a metal hyperaccumulating plant species, the Zn/Cd hyperaccumulator, Thlaspi caerulescens, as an example for plant heavy metal research. Based on the specific cases considered in this paper, it appears that quite different strategies are used for Al and heavy metal resistance. For Al, our current understanding of a resistance mechanism based on excluding soil-borne Al from the root apex is presented. For heavy metals, a totally different strategy based on extreme tolerance and metal hyperaccumulation is described for a hyperaccumulator plant species that has evolved on naturally metalliferous soils. The reason these two strategies are the focus of this paper is that, currently, they are the best understood mechanisms of metal resistance in terrestrial plants. However, it is likely that other mechanisms of Al and/or heavy metal resistance are also operating in certain plant species, and there may be common features shared for dealing with Al and heavy resistance. Future research may uncover a number of novel metal resistance mechanisms in plants. Certainly the complex genetics of Al resistance in some crop plant species, such as rice and maize, suggests that a number of presently unidentified mechanisms are part of an overall strategy of metal resistance in crop plants.     

Chemical reaction- and particle diffusion-based kinetic modeling of metal biosorption by a Phormidium sp.-dominated cyanobacterial mat

The present study explores the suitability of chemical reaction-based and diffusion-based kinetic models for defining the biosorption of Cu(II), Cd(II) and Pb(II) by Phormidium sp.-dominated mat. The time-course data of metal sorption by the test mat significantly (r² = 0.932-0.999) fitted to the chemical reaction-based models namely pseudo-first-order, -second-order, and the general rate law. However, these models fail to accurately describe the kinetics of metal biosorption due either to prefixed order or unjustifiable change in rate constant and reaction order with varying concentrations of metal and biomass in the solution. The diffusion-based models, namely, the intra-particle diffusion model and the external mass transfer model fitted well to the time-course metal sorption data, thus suggesting involvement of both external and intra-particle diffusion processes in sorption of test metals by mat biomass. However, the Boyd kinetic expression clearly showed that the external mass transfer is the dominant process.     

The accumulation characteristics and potential health risks of heavy metals in vegetables from reclaimed area of China

The reclamation of subsidence area was regarded as a useful pathway to rebuild landscape and ecosystem. However, the elevated concentrations of heavy metals in the reclaimed area may lead to potential environmental and health risks. This study was aimed at investigating the accumulation of heavy metals in the soils and vegetables, and evaluate the potential health risks to human beings via consuming these vegetables. The concentrations of heavy metals (Cd, Cu, Pb, and Zn) were measured by using inductively coupled plasma mass spectrometry. The elevated concentrations of heavy metals were found in the soil from the reclaimed area when compared with the background value. The concentrations of heavy metals were various among the different vegetable species. The heavy metal tolerance could be found in all the selected vegetables. The elevated concentrations of Cu, Pb, and Zn in the edible part of the selected vegetables indicated that the consumption of these vegetables may lead to potential health risk. The intake of soybean, radish, sweet potato, and mugwort may lead to potential health risks due to the elevated target health quotients. Chinese cabbage and pepper were regarded as the suitable vegetables which may help in reducing the potential health risk.     

Modeling studies on mono and binary component biosorption of phenol and cyanide from aqueous solution onto activated carbon derived from saw dust

Biosorption is an effective treatment method for the removal of phenol and cyanide from aqueous solution by saw dust activated carbon (SDAC). Batch experiments were achieved as a function of several experimental parameters, i.e. influence of biosorbent dose (5–60 g/L) contact time (2–40 h), pH (4–12), initial phenol concentration (100–1000 mg/L) and initial cyanide concentration (10–100 mg/L) and temperature (20–40 °C). The biosorption capacities of the biosorbent were detected as 178.85 mg/g for phenol with 300 mg/L of initial concentration and 0.82 mg/g for cyanide with 30 mg/L of initial concentration. The optimum pH is found to be 8 for phenol and 9 for cyanide biosorption. The mono component biosorption equilibrium data for both phenol and cyanide were well defined by Redlich–Peterson model and binary component adsorption equilibrium data well fitted by extended Freundlich model. The percentage removal of phenol and cyanide using SDAC was 66.67% and 73.33%, respectively. Equilibrium established within 30 h for phenol and 28 h for cyanide. Kinetic studies revealed that biosorption of phenol followed pseudo second order indicating adsorption through chemisorption and cyanide followed pseudo first order kinetic model indicating adsorption through physisorption. Thermodynamic studies parameters, i.e., enthalpy (Δh₀), entropy (ΔS₀) and Gibb’s free energy (ΔG₀) have also been considered for the system. Thermodynamic modeling studies revealed that the process of cyanide biosorption was endothermic and phenol biosorption was exothermic in nature.     

Application of Freundlich and Langmuir models to multistage purification process to remove heavy metal ions by using Schizomeris leibleinii

The adsorption of iron(III), lead(II) and cadmium(II) ions onto Schizomeris leibleinii, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration to determine the optimum adsorption conditions. Optimum initial pH for iron(III), lead(II) and cadmium(II) ions were 2.5, 4.5 and 5.0 at optimum temperature 30°C, respectively. The initial adsorption rates increased with increasing initial iron(III), lead(II) and cadmium(II) ion concentrations up to 100, 100 and 150 mg l⁻¹, respectively. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. The adsorption of these metal ions to S. leibleinii was investigated in a two-stage mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given ‘quantity of dried algae (X₀)/volume of solution containing heavy metal ion (V₀)’ ratio were calculated using Freundlich and Langmuir isotherm constants. The experimental biosorption equilibrium data for iron(III), lead(II) and cadmium(II) ions were in good agreement with those calculated by both Freundlich and Langmuir models. The adsorbed iron(III), lead(II) and cadmium(II) ion concentrations increased with increasing X₀/V₀ ratios while the adsorbed metal quantities per unit mass of dried algae decreased.     

Determination of heavy metals in eggs of Little Grebe (Tachybaptus ruficollis) around the wastewater treatment ponds,Khon Kaen University

Bird eggs can often be used as a bioindicator of potential effects in environment pollutions. Little Grebe (Tachybaptus ruficollis) lays the eggs around wastewater treatment ponds, Khon Kaen University. The aim of this study is to determine the contamination level of Hg, Pb, Cd, Cr, and Cu in egg content, eggshell and to relate hatching success. Fifteen eggs, four sludge samples, and wastewater samples were collected during September 2016 to April 2017 and were digested and determined using ICP-MS. Clutch size was 1–6 eggs and the weight, width, and length of eggs (mean ± SD) were 11.64 ± 0.91 g., 24.96 ± 0.85 mm, 35.05 ± 1.32 mm, respectively. Hatching success (n = 15) was 96.7%. Cu and Pb were detected at low level in wastewater, and five heavy metals were contaminated in sludge samples. Cu> Cr> Pb> Hg were detected in egg samples (n = 15), and all concentrations in egg content were more than in eggshell. Cr, Cu, Pb, and Hg concentration were not correlated between eggshell and egg content. This study indicated that the heavy metals can be contaminated in sediment, wastewater and can be transferred to egg of Little Grebes. These suggest the ecological risk of heavy metals on other long-living vertebrates living in the area.     

A natural macroalgae consortium for biosorption of copper from aqueous solution: Optimization,modeling and design studies

In this study, the capacity of a natural macroalgae consortium consisting of Chaetomorpha sp., Polysiphonia sp., Ulva sp. and Cystoseira sp. species for the removal of copper ions from aqueous environment was investigated at different operating conditions, such as solution pH, copper ion concentration and contact time. These environmental parameters affecting the biosorption process were optimized on the basis of batch experiments. The experimentally obtained data for the biosorption of copper ions onto the macroalgae-based biosorbent were modeled using the isotherm models of Freundlich, Langmuir, Sips and Dubinin–Radushkevich and the kinetic models of pseudo-first-order, pseudo-second-order, Elovich and Weber and Morris. The pseudo-first-order and Sips equations were the most suitable models to describe the copper biosorption from aqueous solution. The thermodynamic data revealed the feasibility, spontaneity and physical nature of biosorption process. Based on the data of Sips isotherm model, the biosorption capacity of biosorbent for copper ions was calculated as 105.370 mg g^?1 under the optimum operating conditions. A single-stage batch biosorption system was developed to predict the real-scale-based copper removal performance of biosorbent. The results of this investigation showed the potential utility of macroalgae consortium for the biosorption of copper ions from aqueous medium.     

Effect of wastewater sludge on growth and heavy metal bioaccumulation of two Salix species

Fast-growing tree species, such as willows, can benefit from sludge application. While sludges are good fertilizers, they may contain heavy metals which could reduce productivity and cause environment risks. The aims of the present research were to: i) determine the biomass production of Salix discolor Mühl. and Salix viminalis L. when supplied with various amounts of dried and pelleted sludge and ii) assess the uptake and accumulation of heavy metals. Trials were carried out using unrooted cuttings that were planted in large plastic pots containing sandy soil and grown outdoors for a 20-week period. Five doses of sludge were applied: the equivalents of 0 (T0), 40 (T1), 80 (T2), 120 (T3), 160 (T4) and 200 (T5) kg “available” N ha^-1. Trees which received the highest dosage of sludge showed the best growth. Stem biomass was significantly greater for S. viminalis which had received sludge treatments. The relationship between the total biomass yield Y (g) and the rate of fertilization X (equivalent to kg of “available” nitrogen provided per hectare) is linear. Regression equations of predicted biomass production were established as follows: S. discolor, Y=28.36+0.56X and S. viminalis, Y=39.95+0.64X. For both species, the greatest stem biomass per g of N applied was produced with treatment 4 and 5. Amounts of nitrogen per leaf area (N/LA) and per dry leaf mass (N/DL) were higher for S. viminalis. The metal transfer coefficient did not vary between the species but was significantly different for Cd and Zn. Plants were able to absorb Cd and Zn, but were less able to absorb Ni, Hg, Cu, and Pb. It was concluded that the dried and pelleted sludge is a good fertilizer. S. discolor and particularly S. viminalis can be used as filters for the purification of wastewater sludge as well as for biomass production purposes. R F Huettl Section editor     

NMR studies on heavy metal immobilization in biosorbents and mineral matrices

Magnetic resonance imaging and otherNMR methods have a potential for thenon-destructive observation of environmentallyrelevant processes with both spatial andtemporal resolution. Among other applications,such methods can be used to study transport andimmobilization of paramagnetic heavy metal ionsin biosorbents and other matrices. Thisoverview covers various NMR approaches to studysuch processes and illustrates them withexamples of imaging on alginate-basedbiosorbents and on heavy-metal doped gypsumpastes. Experimental challenges in studies ofother matrices are shortly addressed as well.     

Combining strains of lactic acid bacteria may reduce their toxin and heavy metal removal efficiency from aqueous solution

Aims: The primary objective of this study was to compare the removal of cadmium, lead, aflatoxin B₁ and microcystin‐LR from aqueous solution by Lactobacillus rhamnosus GG, L. rhamnosus LC705, Propionibacterium freudenreichii shermanii JS and Bifidobacterium breve Bbi99/E8, separately and in combination. Methods and Results: The removal of toxins and heavy metals was assessed in batch experiments. The removal of all compounds was observed to be strain specific. The removal of lead by a combination of all the strains used was observed to be lower than could be predicted from the removal by single strains (P < 0·05). A similar trend was also observed with the other compounds studied. Conclusions: The results show that the toxin‐removal capacity of a combination of strains of lactic acid bacteria is not the sum of their individual capacities. Therefore, pure single strains should be used when the goal is to remove single compounds. The use of combinations of strains may be beneficial when several compounds are removed together. This needs to be studied in future experiments. Significance and Impact of the Study: Lactic acid bacteria have been identified as potent tools for the decontamination of heavy metals, cyanotoxins and mycotoxins. The results of this study should be considered when selecting combinations of bacteria for the simultaneous removal of several toxic compounds.