Fundamental aspects of biosorption of lead (II) ions onto a Rhodococcus opacus strain for environmental applications

Lead is present in different types of industrial effluents, being responsible for environmental pollution. Biosorption of heavy metal ions by biological material is a promising technology with a potential for treating mineral processing wastewater. In this fundamental work, the biosorption of Pb(II) ions from aqueous solutions using the bacteria Rhodococcus opacus was investigated as a function of contact time, initial metal ion concentration and temperature. The equilibrium studies showed that the biosorption is well described through the Langmuir isotherm model in comparison to the Freundlich model in the concentration range studied (20–200 mg/L). The biosorption capacity obtained from Langmuir equation increased from 86.2 to 95.2 mg/g as the temperature was increased from 15 to 35 °C. Experimental data were also tested in terms of biosorption kinetics using pseudo-first order and pseudo-second-order kinetic models. The result showed that the biosorption processes of lead ions followed well pseudo-second-order kinetics and the adsorption rate constant increased with increasing temperature. The activation energy of biosorption (E_a) was determined (30.4 kJ/mol) using the pseudo-second-order rate constants. The positive values of both ΔH⁰ and ΔS⁰ obtained suggest that the biosorption of lead (II) ion on the R. opacus was spontaneous and endothermic in nature.     

Evaluation of equilibrium, kinetic and thermodynamic parameters for biosorption of nickel(II) ions onto bacteria strain, Rhodococcus opacus

The present study explores the ability of Rhodococcus opacus bacteria strain for the removal of nickel(II) under different experimental conditions. The effects of relevant parameters such as solution pH, biomass loading, ionic strength, and temperature on nickel(II) biosorption capacity were evaluated. Although the tests were carried out using synthetic solutions, the results are representative of typical waste effluents from chemical, dyestuffs, battery manufacture, porcelain enameling, metallurgical industries and electroplating circuits. The sorption data followed the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Sips isotherms. The maximum sorption capacity was found to be 7.63 mg g⁻¹ at pH 5. Thermodynamic parameters have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constants for different kinetic models were calculated. The activation energy of biosorption (E_a) was determined as 12.56 kJ mol⁻¹ using the Arrhenius equation.     

Biosorptive removal of Cd and Zn from liquid streams with a Rhodococcus opacus strain

The biosorption abilities of Rhodococcus opacus were studied for cadmium and zinc removal for liquid aqueous streams. The influence of pH, initial metal concentration and time removal were evaluated on the biosorption studies, in a batch scale basis. The Cd²⁺ and Zn²⁺ species uptake capacity by R. opacus has been also compared using Langmuir and Freundlich models. At pH 7.0 and 26 °C C, Cd²⁺ removal achieved a value around 60% from an initial concentration of 15 ppm. On the other hand, Zn removal achieved a value around 88% from an initial concentration of 5 ppm. Kinetics studies revealed that the biosorption process followed a pseudo-second order model for the two metal species (Cd²⁺ and Zn²⁺) and the kinetic constants were 3.90 and 3.37 g mg⁻¹ min⁻¹, for an initial concentration of 15 and 5 ppm for cadmium and zinc, respectively. The results showed that the R. opacus is a potential engineering biosorbent for environmental and extractive metallurgy sustainable applications.     

Heavy metals removal from solution by palygorskite clay

The possible use of palygorskite clay, mined in the Dwaalboom area of the Northern Province of South Africa, as an adsorbent for the removal of metal ions such as lead, nickel, chromium and copper from aqueous solution, was investigated. In this work, adsorption of these metals onto palygorskite has been studied by using a batch method at room temperature. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between experimental data and the model-predicted values was expressed by the correlation coefficient (R²). The Langmuir model represented the sorption process better than the Freundlich one, with correlation coefficient (R²) values ranging from 0.953 to 0.994. The adsorption capacity (Q₀) calculated from the Langmuir isotherm was 62.1 mg Pb(II) g⁻¹, 33.4 mg Ni(II) g⁻¹, 58.5 mg Cr(VI) g⁻¹ and 30.7 mg Cu(II) g⁻¹ at a pH of 7.0 at 25 ± 1 °C for a clay particle size of 125 μm. Kinetic investigations were performed to investigate the rate of adsorption of metal ions. The Lagergren’s first-order rate constants were calculated for different initial concentrations of metal ions. In batch mode adsorption studies, removal increased with an increase of contact time, adsorbent amount and solution pH. Adsorption of metals from the single-metal solutions was in the order: Pb > Cr > Ni > Cu. Data from this study proved that metal cations from aqueous solution can be adsorbed successfully in significant amounts by palygorskite. This opens up new possibilities and potential commercial uses in the palygorskite market.     

Sorption of Zn,Cd and Cr on calcite. Application to purification of industrial wastewaters

Batch and column sorption studies of Zn, Cd and Cr were conducted on calcite to determine its retention capacity for these elements commonly present in industrial effluents and to explore its behaviour as a purification filter in a continuous flow system. The Langmuir model was found to describe the sorption processes best, and the results show that calcite is suitable for the purification of industrial wastewaters down to the concentration limits prescribed by current legislation, with sorption capacities depending on the metal sorbed in the order Cr>Zn>Cd.X-ray photoelectron spectroscopy (XPS) analyses were performed with the samples: calcite–Cr, calcite–Zn, calcite–Cd and pure calcite to determine the sorption mechanisms of these metals on calcite. The results show that Cd precipitates on calcite surface after a first step of Cd adsorption via exchange with Ca, the Zn retention on calcite occurs by precipitation as hydrozincite, Zn₅(OH)₆(CO₃)₂, and Cr precipitates on calcite as a coating of oxide hydrocarbonate.     

Tailings Weathering and Arsenic Mobility at the Abandoned Zgounder Silver Mine,Morocco

The abandoned Zgounder Mine (Morocco) was exploited for Ag from 1982 to 1990 and generated nearly 490,000 t of mill tailings before it was closed without being reclaimed. The tailings contain low concentrations of sulfide (mainly as pyrite, sphalerite, and galena) and carbonates (mainly dolomite). Silicates (muscovite, albite, chlorite, labradorite, actinolite, and orthoclase) occur in high concentrations. The most abundant trace elements are As, Ti, Fe, Mn, Zn, and Pb. We studied the geochemical behavior of the mine wastes to identify the main factors controlling drainage water chemistry. Particular emphasis was put on sorption phenomena to explain the low As concentrations in the leachates despite significant As levels in the tailings. Weathering cell tests carried out on various tailings produced two types of contaminated drainage: acidic and neutral. The kinetic test leachates contained high concentrations of some contaminants, including As (0.8 mg L^?1), Co (11 mg L^?1), Cu (34 mg L^?1), Fe (70 mg L^?1), Mn (126 mg L^?1), and Zn (314 mg L^?1). Acidity and contaminants in the leachates were controlled by dissolution of soluble salts and Fe hydrolysis rather than sulfide oxidation. Batch sorption tests quantified the significance of As sorption, and sequential extraction showed that most of the As sorption was associated with the reducible fractions (Fe and Mn oxides and oxyhydroxides).     

Simultaneous uptake of metals by activated sludge

The adsorption of three metal ions, Cu, Cd and Zn, in a bicomponent mixture system by activated sludge was investigated. Two-metal sorption system efficiency was evaluated by replacing simple isotherm curves by 3-D sorption isotherm surfaces. In order to describe isotherm surfaces mathematically, three empirical models were used. The isotherms indicated a competitive uptake with Cu being preferentially adsorbed followed by Cd and Zn. For instance, at C_f[Cd]=0.9 mmol/l and with 0.5 and 2 mmol/l Cu in the system, the Cd uptake was 0.17 and 0.08 mmol/g, respectively. Therefore, a 53% decrease of Cd biosorption was observed when Cu was present at the highest concentration. On the other hand, 0.9 mmol/l Cd caused a reduction of 54% on the Cu uptake [q(Cu)=0.28 mmol/g] in comparison with the results obtained when Cd was present at 0.225 mmol/l [q(Cu)=0.13 mmol/g]. The interference of Zn with the Cu and Cd uptake was much less pronounced and was observed at much higher ratios of Zn:Cu and Zn:Cd concentrations. 83% of the total metal uptake was due to Cu when the residual concentrations of Cu and Zn were the same (e.g., either 0.5 or 1 mmol/l each one). On the other hand, when the residual concentrations of Cd and Zn were the same (e.g., either 0.5 or 1.5 mmol/l each one), about 71% of the total metal uptake was due to Cd uptake.     

Single and binary component sorption of the fission products Sr2+, Cs+ and Co2+ from aqueous solutions onto sulphate reducing bacteria

This study investigates the removal of the fission products Sr²⁺, Cs⁺ and Co²⁺ in single and binary metal solutions by a sulphate reducing bacteria (SRB) biomass. The effect of initial concentration and pH on the sorption kinetics of each metal was evaluated in single metal solutions. Binary component equilibrium sorption studies were performed to investigate the competitive binding behaviour of each metal in the presence of a secondary metal ion. Results obtained from single metal equilibrium sorption studies indicated that SRB have a higher binding capacity for Sr²⁺ (q_max = 416.7 mg g^?1), followed by Cs⁺ (q_max = 238.1 mg g^?1), and lastly Co²⁺ (q_max = 204.1 mg g^?1). Among the binary systems investigated, Co²⁺ uptake was the most sensitive, resulting in a 76% reduction of the sorption capacity (q_max) in the presence of Cs⁺. These findings are significant for future development of effective biological processes for radioactive waste management under realistic conditions.     

Biosorption of Cu(II) and Pb(II) from aqueous solutions by dried activated sludge

The biosorption of Cu(II) and Pb(II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial metal ion concentration and temperature. The results showed that both the heavy metals uptake processes followed the pseudo-second-order equation. The equilibrium data fitted very well to both Langmuir and Freundlich adsorption models. The main mechanism of Cu(II) and Pb(II) biosorption on dried activated sludge was their binding with amide I group.     

Effect of mining chemicals on biosorption of Cu(II) by the non-living biomass of the macrophyte Potamogeton lucens

The present work investigates the effect of some compounds commonly discharged from mineral processing plants on biosorption of heavy metals by the non-living biomass of the freshwater macrophyte Potamogeton lucens. Studies of sorption of Cu (II) in the presence of metal ions, surfactants, EDTA and cyanide were carried out at laboratory scale. The results show that copper adsorption by ion exchange on the biomass is not affected by equimolar concentrations of copper/sodium, copper/calcium or copper/iron. Non ionic surfactants (e.g. pine oil) do not modify biosorption, but the negative groups of anionic surfactants (e.g. sodium oleate) compete with the surface groups of the biomass for the free copper ions in solution. EDTA and cyanide react with copper ions producing soluble complexes that do not adsorb onto the biomass. The biosorption process is suitable for wastewater treatment when the heavy metal species are free in solution. Effluents containing metal sequestering compounds that produce soluble or precipitated species are not able to be treated by carboxyl groups based biosorbents.     

Changes in Efficiency and Hydraulic Parameters During the Passive Treatment of Ferriferous Acid Mine Drainage in Biochemical Reactors

The objective of this study was to evaluate the effects of different reactive mixtures and hydraulic retention times (HRTs) on hydraulic parameters (hydraulic conductivity, k_sat, and porosity) and the efficiency of passive biochemical reactors (PBRs) for treatment of ferriferous acid mine drainage (AMD). Five 10.7 L PBRs were filled with three reactive mixtures, containing either a carbon-rich substrate (60% w/w) or an inert/neutralizing agent (50% w/w). The PBRs were tested over a 450 day period using two qualities of iron-rich AMD (4 and 1 g L^?1 Fe in AMD1 and AMD2, respectively), and two HRTs, of 5 and 7 days. During the last week of the columns’ operation, a tracer test (5 g L^?1 of NaCl) was also performed, in addition to monthly measurements using the falling head method. Changes in HRT and k_sat were evaluated throughout the experiment. The PBRs increased the pH of AMD influents from 3.5 to 6 and efficiently removed Al, Cd, Cr, Ni, Pb, and Zn (>?90%), whereas Fe was only partially and inconsistently treated. No significant differences were observed among the three tested mixtures, regardless of the HRT or the AMD quality. Results from the tracer test and k_sat measurements showed no significant decrease in the initial values of the hydraulic parameters with time except for column 3, where a slight decrease was observed. Although sorption could have been important during the start-up of the PBRs, post-testing characterization of the spent reactive mixtures showed that the Fe was mainly retained as oxy-hydroxides and sulfides. Given the PBRs’ marginal effectiveness for Fe-rich AMD, pre-treatment removal of the iron is recommended.     

Biological Removal of High Loads of Thiosulfate Using a Trickling Filter Under Alkaline Conditions

Uncontrolled release of thiosulfate can cause high oxygen demand, or generate toxic compounds under anaerobic scenarios. Biooxidation of thiosulfate in a biotrickling filter (BTF) colonized by an alkaliphilic sulfide-oxidizing bacterial consortium was studied at pH ≈10. Inlet thiosulfate concentrations were varied from 3.5 to 21.3 g L^?1, with a residence time of 216 s, emulating conditions encountered in wastewater from mining processes. Sulfate production, oxygen concentration, and biomass in both packing and effluent were periodically analyzed to characterize bioreactor performance. Removal efficiencies near 100 % were obtained during the entire experimental period, with a maximum elimination capacity of 242 g thiosulfate m^?3 h^?1. Although the BTF was able to transfer large amounts of oxygen to biooxidize thiosulfate to sulfate, under high initial thiosulfate loads, thiosulfate was not completely oxidized to sulfate, since biooxidation was conditioned to oxygen supply. Respirometric tests performed to investigate biomass adaptation and activity revealed oxygen consumption values of 0.5 mmol O₂ (g protein)^?1 min^?1 for the period with the highest thiosulfate inlet load.     

微波联合碱改性粉煤灰对铬(Ⅵ)的吸附性能

为了强化改性粉煤灰在重金属废水处理中的吸附效果,利用微波联合碱改性的方法,研究微波温度、微波时间、微波功率等制备条件对改性粉煤灰吸附铬(Ⅵ)的影响以及吸附等温特性。结果表明,粉煤灰改性的最佳制备条件为:微波功率600 W,微波温度60℃,微波时间15 min,吸附量达到0.341 mg/g,较改性前提高50%以上。此改性条件下的粉煤灰进行吸附等温的试验研究结果表明,其对铬(Ⅵ)的吸附符合Freundlich和Langmuir等温吸附模型,此吸附过程为单分子层吸附。粉煤灰具有较高的经济性,可广泛用于含铬(Ⅵ)废水的处理。      

天然膨润土对Cr(VI)的吸附动力学及等温线研究

研究所用膨润土的主要成分为SiO₂和Al₂O₃,属于钙基膨润土,BET表面积为47.98 m₂/g。在恒温及恒定pH条件下,用动态吸附法研究了膨润土对Cr(VI)的吸附特性,结果表明其较好符合Lagergren二级吸附速率方程。利用Langmuir等温线方程和Freundlich等温线方程对动态吸附过程进行拟合,发现其吸附等温反应与Langmuir等温线更适合,属于表面单分子吸附。     

Competitive Removal of Metals from Wastewater by Maghemite Nanoparticles: A Comparison Between Simulated Wastewater and AMD

Maghemite nanoparticles (γ-Fe₂O₃) produced using a recently developed, single-step method proved to be highly effective for selective removal of Cu, Ni, Mn, Cd(II), and Cr(VI) from acid mine drainage (AMD) and simulated wastewater. An average particle size of about 14 nm was estimated for the maghemite nano-particles using transmission electron microscopy. Their adsorption characteristics proved to be highly pH dependent, allowing facilitated selective adsorption of the studied metals, all of which followed the Langmuir adsorption model. In both simulated wastewater and AMD, Cr(VI) adsorption was best at 70 °C and pH = 2.6. Adsorption peaked at pH = 8.5 for Ni(II), 10 for Cd(II), 8.5 for Mn(II), and 6.5 for Cu(II).     

A Spatial Mixing Model to Assess Groundwater Dynamics Affected by Mining in a Coastal Fractured Aquifer,China

A linear mixing model method based on principal component analysis (PCA) in three-dimensional space was used to assess groundwater dynamics. PCA was performed on a series of hydrochemical datasets collected from 2009 to 2014 (except in 2010). The results of PCA and a prior conceptual model were used to identify the evolution and potential end-members of water. Then, a mixing calculation code was applied to compute the mixing proportions, and the results were used to reconstruct the mixing process. Deviations were evaluated by comparing the computed and measured concentrations of ions. The accuracy of this method was compared to that of a 2D model that was based on only conservative ions and a 3D model developed in this study that does not consider the water’s physical parameters. The results indicated that the method that considered all of the measured ions, stable isotopes, and physical parameters, performed well. Its accuracy was demonstrated by good agreement between its measured and simulated values. The mean values of deviation for δ¹⁸O, δD, K, Na, Ca, Mg, Cl, and SO₄ were 0.26, 0.51, 0.19, 0.08, 0.21, 0.15, 0.05, and 0.08, respectively. Five water sources and their groundwater dynamics were interpreted using this model; the results demonstrated that mining has had a substantial influence on the groundwater flow system in both the vertical and lateral directions. Above a depth of -375 m, freshwater is the dominant source, and its proportions in most sites exceeds 40%. Seawater has reached a depth of ? 510 m, and its maximum proportion of 82% can be observed at 510-2a. Quaternary water recharged the area between F3 and the prospecting line 2230. Its proportion exceeded 45% at most sites. The recharge depth reached ??510 m at most sites and ??600 m at some sites. Calcium-rich and Mg-rich water were distributed above and below ??510 m, respectively. These distinguishing features indicate that induced ground deformation broke through the Quaternary aquifuge and increased the vertical recharge in the tensional zone, while preventing vertical recharge in the compressive zone at the subsidence center.     

Impact of organic amendments on aerial biomass production,and phytoavailability and fractionation of copper in a slightly alkaline copper mine tailing

In the process of phytoremediation of mine tailing land, the bioavailability of heavy metals is an important factor. Greenhouse experiment was conducted to assess the availability and uptake of copper (Cu) by maize (Zea mays L.) grown on a slightly alkaline Cu-mine tailing amended with commercial compost and chelators. A second objective was to evaluate the distribution of Cu in cultivated Cu-mine tailings. The experimental design consisted of 12 treatments resulting from the combination of four rates (0, 5, 10 and 20%, by humid weight) of peat moss-shrimp wastes compost and three rates (0, 1.2 and 2.4 dm³) of organic complexing agents applied as a 0.0025 M EDTA + 0.001 M citric acid solution before plant harvest. The results showed that compost and chelators had a positive effect on top biomass production of maize. Compared with the control, the application of compost decreased Cu_CAR and increased Cu_ORG whereas the addition of chelating solution increased Cu_SOL and Cu_EXC and decreased Cu_CAR and Cu_ORG. The Cu lability in cultivated tailing and its availability to the maize plant are highly dependent on the metal speciation in tailing. In another series of experiments, sorption of Cu by cultivated mine tailings were examined. The amounts of Cu sorbed and K _d values were highest in tailing amended with highest compost rate, and were positively correlated with tailing organic matter (OM) content and Cu bound to Cu_ORG. The results indicate that peat moss and shrimp waste containing compost could be used as a phytostabilizer by supplying OM and nutrients and as a sorbent by mitigating Cu uptake by maize. This compost is able to improve the phytoremediation of Cu-mine tailings.     

Gas diffusion coefficient in coal: calculation of tangent slope accuracy through the inflection point determination

This investigation aims to develop an accurate method to calculate the tangent slope (b) - a fundamental parameter to calculate gas diffusion coefficients under different pressures - using inflection point determinations. The authors also studied the different tangent slope behaviours depending on the experimental gas sorption used. The single Langmuir model for individual gases and the extended Langmuir model, for multicomponent gas mixtures were applied to fit experimental gas sorption isotherm data. Two coals were selected in order to minimize and/or avoid the maceral composition and vitrinite mean random reflectance effects. Samples were submitted to three different gas compositions, viz. 99.999% CH₄; 99.999% CO₂; and a gas mixture containing 74.99% CH₄ + 19.99% CO₂ + 5.02% N₂. Results showed that the first and the second derivatives calculated to define the first inflection points represent exactly the final limit of tangent slopes.     

Biosorption of cadmium by green coconut shell powder

The effective removal of heavy metals from aqueous wastes is among the most important issues for many industrialized countries. The traditional treatment methods used to remove heavy metals from wastewaters have certain disadvantages such as incomplete metal removal, high reagent and energy requirements, generation of toxic sludge or other waste products that require disposal. The search for alternative and innovate treatment techniques has focused attention on the use of biological materials for metal removal and recovery technologies. Biosorption has gained important credibility during recent years because of its good performance and low cost.In the present study, the biosorption capacity of powder from coconut shell was studied for cadmium. The adsorption capacity of biomass was investigated by batch experiments. The influence of metal ion concentration and pH were evaluated and the results were fitted using adsorption isotherm models. The kinetic of cadmium biosorption was also investigated.     

Hydrogeochemistry and Contamination of Trace Elements in Cu-Porphyry Mine Tailings: A Case Study from the Sarcheshmeh Mine,SE Iran

Geochemical and hydrochemical investigations were performed to understand the contamination potential of the Sarcheshmeh mine tailings. The geochemical mobility for the tailings is as follows: Cu > Cd > Co > Zn > Ni > Mn > S > Cr > Sn > As > Se > Fe = Bi > Sb = Pb = Mo. Highly mobile and contaminant elements (Cd, Cu, Zn, Mn, Co, Ni, S, and Cr), which significantly correlated with each other, were mainly concentrated in the surface evaporative layer of the old, weathered tailings, due to the high evaporation rate, which causes subsurface water to migrate upward via capillary action. The contamination potential associated with the tailings is controlled by: (1) dissolution of secondary evaporative soluble phases, especially after rainfall on the old weathered tailings, accompanied by low pH and high contamination loads of Al, Cd, Co, Mg, Cr, Cu, Mn, Ni, S, Se, and Zn; (2) processing of the Cu-porphyry ore under alkaline conditions, which is responsible for the high Mo (mean of 2.55 mg/L) and very low values of other contaminants in fresh tailings in the decantation pond; (3) low mobility of As, Fe, Pb, Sb, Mo, and Sn due to natural adsorption and co-precipitation in the tailings oxidizing zone. Speciation modeling showed that sulfate complexes (MSO₄ ⁺, M(SO₄)_(aq), M(SO₄) ₂ ^?2 , and M(SO₄) ₂ ^? ) and free metal species (M⁺² and M⁺³) are the dominant forms of dissolved cations in the acidic waters associated with the weathered tailings. In the alkaline and highly alkaline waters, trace element speciation was controlled by various hydroxide complexes, such as M(OH)⁺, M(OH) ₃ ^? , M₃(OH) ₄ ⁺² , M₂(OH) ₃ ⁺ , M(OH)_2(aq), M(OH) ₄ ^?2 , Me(OH) ₂ ⁺ , Me(OH) ₄ ^? , Me(OH) ₂ ⁺ , Me(OH)_3(aq), and Me(OH) ₄ ^? (where M represents bivalent and Me represents trivalent cations). The speciation pattern of As, Mo, and Se is mainly dominated by oxy-anion forms. The obtained results can be used as a basis for environmental management of the Cu-porphyry mine tailings.