Chemical equilibrium modeling of copper precipitation in a hyper-concentrated solid-liquid system

Rapid progress has been made recently in the understanding of heavy metal sorption and speciation on sediment and soils. One aspect that was overlooked in the previous studies was the process of pollutant transformation and transportation in hyper-concentrated solid-liquid systems. In this paper, batch experiments on copper sorption in association with loess at high sediment concentrations were conducted. However, some reaction mechanisms were difficult to determine experimentally due to the limitations of speciation extraction methods. In an additional study, the MINTEQA2 chemical equilibrium model was used to calculate the speciation and precipitation of copper sorption by loess to give quantitative predictions and detailed information about the reaction process. The experiments and the modeling simulation were made under the same sorption conditions, with sediment concentrations ranging from 50 to 200 kg/m³ and adsorbates of CuSO₄ and Cu(NO₃)₂, in order to compare their results. The modeling results clearly supported the experimental results, fully explained the mechanisms of the effects of chemical form and sediment concentration on the copper sorption, and strengthened the dominant role of carbonates among the main components of loess in the process of copper sorption.     

废啤酒酵母吸附水溶液中Cu2+的性能及机理研究

用废啤酒酵母吸附水溶液中Cu2+,考察了溶液pH值、Cu2+浓度和吸附时间对Cu2+吸附的影响。结果表明：废啤酒酵母吸附Cu2+在4-6个小时内达到吸附平衡,酸性条件利于吸附,以pH为5时最佳,吸附等温曲线符合Langmuir模式。用电位滴定及FTIR分析的方法确定生物吸附剂主要含有磺酸基、羧基及氨基等功能团。生物吸附剂对Cu2+的吸附以单分子层的化学吸附为主,功能团在不同的pH条件下呈现不同的电离性能,在吸附过程中发挥重要作用。     

Sorption of Cu(II) and Cd(II) by extracellular polymeric substances (EPS) from Aspergillus fumigatus

Sorption of Cu(II) and Cd(II) onto the extracellular polymeric substances (EPS) produced by Aspergillus fumigatus was investigated for the initial pH of the solution, EPS concentrations, contact time, NaCl concentration, initial metal ion concentration and the presence of other ions in the solution. The results showed that the adsorption of metal ions was significantly affected by pH, EPS concentrations, initial metal concentration, NaCl concentration and co-ions. The sorption of Cu(II) and Cd(II) increased with increasing pH and initial metal ion concentration but decreased with an increase in the NaCl concentration. The maximum sorption capacities of A. fumigatus EPS calculated from the Langmuir model were 40 mg g⁻¹ EPS and 85.5 mg g⁻¹ EPS for Cu(II) and Cd(II), respectively. The binary metal sorption experiments showed a selective metal binding affinity in the order of Cu(II) > Pb(II) > Cd(II). Both the Freundlich and Langmuir adsorption models described the sorption of Cu(II) and Cd(II) by the EPS of A. fumigatus adequately. Fourier transform infrared spectroscopy (FTIR) analysis revealed that carboxyl, amide and hydroxyl functional groups were mainly correlated with the sorption of Cu(II) and Cd(II). Energy dispersive X-ray (EDX) system analysis revealed that the ion-exchange was an important mechanism involved in the Cu(II) and Cd(II) sorption process taking place on EPS.     

Effect of clay,organic matter and CaCO3 content on zinc adsorption by soils

Summary Zinc adsorption was studied in suspensions of six soils of different physicochemical characteristics in dilute ZnSO₄ solutions. At low concentrations, Zn²⁺ adsorption was described by the Langmuir adsorption equation. The calculated Langmuir adsorption maxima were related positively to clay and carbonate content and negatively with organic matter content of soils. Multiple regression analysis revealed that zinc adsorption maxima can be predicted with good precision from information in soil survey reports. When the added Zn²⁺ exceeded the adsorption maximum, the solid phase of zinc controlling its concentration in solution was either zinc hydroxide or carbonate so long as soil carbonates were present. The values of zinc potential also indicated that soils retain Zn²⁺ more strongly than Zn(OH)₂ or carbonate. Postgraduate student Professor of Soils. Professor of Soils.     

Using lignimerin (a recovered organic material from Kraft cellulose mill wastewater) as sorbent for Cu and Zn retention from aqueous solutions

Adsorption of copper and zinc in lignimerin (an organic material mainly composed by lignin, carbohydrate fragments and some extractives) and its acid derivative (H-lignimerin), recovered from Kraft cellulose mill wastewater was examined. A Box–Behnken experiment design, used to optimize lignimerin recovery process, revealed that the type of solvent used for precipitation is a determining factor in the amount of substance obtained. Conversely, batch adsorption studies at pH 4.0 revealed that the maximum adsorption capacities, modeled by the Langmuir equation, were 666.7 and 370.4 mmol kg⁻¹ for Cu(II) and Zn(II), respectively in lignimerin and 232.6 and 312.5 mmol kg⁻¹ for Cu(II) and Zn(II), respectively in H-lignimerin. The adsorption of Cu(II) and Zn(II) through deprotonated hydroxyl and carboxylic groups was the dominant mechanism that may explain the adsorption in both materials. The adsorption capacities indicated that lignimerin, with a molecular mass between 50 and 70 kDa, has a potential use as an organic sorbent for removing copper and zinc from liquid resources.     

The Role of CEC and pH in Cd Retention from Soils of North of Iran

Cadmium (Cd) is a critical environmental chemical in which sorption reactions control its entry into soil solution. The aim of the present study was to evaluate Cd sorption characteristics of some soils of the northern part of Iran with a wide range of physicochemical properties. Duplicates of each sample were equilibrated with solutions containing 5 to 500 mg Cd L^?1 with 0.01 M CaCl₂ as background solution. The quantity of Cd retention was calculated as the difference between initial and equilibrated Cd concentration. Sorption isotherms including Freundlich, Langmuir, Temkin, Dubinin-Radushkevich, and Redlich-Peterson were used to evaluate the behavior of Cd sorption. Cadmium sorption data were well fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms. The constant of Freundlich equation (k_F ) and adsorption maxima (b_L ) of Langmuir equation were related to pH and cation exchange capacity (CEC). The maximum buffering capacity (K_d ) was significantly correlated with pH (R² = 0.52, p ≤ 0.001) and calcium carbonate equivalent (CCE) (R² = 0.63, p ≤ 0.001). Redlich-Peterson constants (k_RP and a_RP ) were significantly correlated with pH (R² k_RP = 0.30, p ≤ 0.007) and (R² a_RP = 0.27, p ≤ 0.012). It seemed that pH, CEC, and CCE were the main soil properties regulating Cd retention behavior of the studied soils.     

黑土和棕壤对铜的吸附研究

研究了黑土与棕壤对Cu吸附的热力学和动力学特性．结果表明,在实验所采用Cu^2+浓度范围内,黑土和棕壤对CU^2+的吸附量均随着加入Cu^2+浓度的增加而增加,但黑土对cu^2+的吸附固定能力明显高于棕壤．在吸附平衡液Cu^2+浓度为95mg·kg^-时,棕壤对cu^2+的吸附量接近3720mg·kg^-1,黑土对Cu^2+的吸附量高达6076mg·kg^-1,最大CuCl2浓度(400mg·kg^-1)时,黑土和棕壤对Cu^2+的吸附量分别达到6159．0和4736．6mg·kg^-1．两种土壤对Cu^2+的吸财等量线与Freundlich和Temkin方程均有较好的拟合性,可以用Freundlich方程对其吸附行为进行描述．Langmuir方程不适宜描述两种土壤对Cu^2+的等温吸附过程．黑土和棕壤对Cu^2+的吸附均较快,最初2min内就可以达到平衡后吸附量的90％以上,在15-20min左右吸附基本达到平衡．描述黑土和棕壤动力学过程的最优模型为双常数速率方程,其次为一级动力学方程和Elovich方程。     

Study of multicompound sorption of Lead and Pyrene on a reconstituted soil: batch and fixed bed column tests

Many polluted sites are simultaneously contaminated with polycyclic aromatic hydrocarbons and heavy metals. In the present study, batch and continuous column experiments were performed utilizing self-composition soil to describe the sorption behavior of two contaminants: lead (Pb²⁺) and pyrene (PYR). Operational conditions such as contact time, bed depth, and flow rate were optimized. The effect of soil organic matter content on the process of adsorption of both contaminants was investigated. The presence of PYR in solution at neutral pH (6.0–7.5) decreased Pb²⁺ sorption. Similar behavior was observed for PYR in the presence of Pb²⁺ in solution. At room temperature, batch experimental data conducted as a function of contact time were analyzed using the Langmuir and Freundlich isotherms. Results revealed that Pb²⁺ sorption isotherms were fitted better by the Langmuir model and PYR sorption isotherms were fitted better by the Freundlich model. Column adsorption experiments were carried out at room temperature and under operating parameters (bed depth, flow rate, and initial contaminant concentration). Breakthrough curves were well fitted to the two-site first-order kinetic model with a sum of square errors less than 0.14. The Pb²⁺ adsorption kinetic data were processed also for the Thomas model with a good accuracy.     

Removal of copper(II) using chitin/chitosan nano-hydroxyapatite composite

Polymeric composites made up of nano-hydroxyapatite (n-HAp) with chitin and chitosan have been prepared and studied for the removal of Cu(II) ions from the aqueous solution. The sorption capacity (SC) of n-HAp, n-HAp/chitin (n-HApC) composite and n-HAp/chitosan (n-HApCs) composite were found to be 4.7, 5.4 and 6.2 mg/g respectively with a minimum contact time of 30 min. Batch adsorption studies were conducted to optimize various equilibrating conditions like contact time, pH and selectivity of metal ion. The sorbents were characterized by FTIR, TEM, XRD and SEM with EDAX analysis. The sorption process was explained with Freundlich and Langmuir isotherms respectively. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated to understand the nature of sorption. A suitable mechanism for copper sorption was established and the selectivity of the metal ions for the composites was identified.     

Copper flotation waste from KGHM as potential sorbent for heavy metal removal from aqueous solutions

Sorption affinity of copper flotation waste from KGHM toward Cd(II), Cr(III), Cu(II), and Pb(II) ions was investigated in this work. Batch sorption studies, using single-element synthetic aqueous solutions at various pH (2–12), contact time (10–300 min), initial concentration (100–5000 mg dm^?3; 1–100 mg dm^?3 for Cd(II)) and adsorbent dose (25–200 g dm^?3), were performed. Bonding strength of adsorbed metals was tested from the degree of desorption. The maximum metal removal was observed at pH 5–8, ≥120 min reaction time, and 25 g dm^?3 adsorbent dose. Maximum sorption capacities of studied material were 41.6, 58.8, and 83.8 mg g^?1 for Cr(III), Cu(II), and Pb(II), respectively, for 5000 mg dm^?3 initial concentration, and 0.86 mg g^?1 for Cd(II) for initial concentration of 50 mg dm^?3. Sorption isotherms were very well fitted to Langmuir (Cd, Cr, Pb) and Freundlich (Cu) models. Sorption kinetics was nearly ideally fitted to pseudo-second-order kinetic model. Desorption studies showed that most of Cr(III) (98.5%) and Pb(II) (67.3%) ions remained bound to the surface, indicating that the chemisorption dominated as a controlling process. On the other hand, mostly desorbed were Cd(II) (98.5%) and Cu(II) (90.3%) ions, which indicated that processes like physisorption or precipitation were prevailing.     

Manganese adsorption by sediment in Wadi Tafna,Algeria

The removal of manganese from aqueous solution by sediment in Wadi Tafna, north-western Algeria, was investigated under batch conditions in 2003. Kinetic data equilibrium removal isotherms were measured at 20 °C. The influence of different experimental parameters, such as contact time, manganese concentration and sediment mass on the removal kinetics of manganese was studied. The content of carbonate in sediment increased the adsorption rate, indicating the active phase towards manganese cations. The process followed pseudo-second-order kinetics. Manganese uptake by sediment was quantitatively evaluated using sorption isotherms. In order to describe the adsorption isotherm mathematically, the experimental data of the removal equilibrium were analysed with Langmuir and Freundlich models revealing that the equilibrium data were perfectly represented using both isotherms.     

Phosphorus sorption characteristics of sediment in the Simiyu and Kagera River basins: implications for phosphorus loading into Lake Victoria

As part of a larger study to assess the influence of land use on riverine and atmospheric phosphorus (P) loading to Lake Victoria, P sorption characteristics of eight composite bottom sediment samples from the Simiyu and Kagera rivers were determined using the Langmuir equation. The samples had low to medium Langmuir adsorption maxima (Γ_m), ranging from 107 to 201μg g^?1. Langmuir binding energy co-efficient (K) ranged from 60 to 181μg l^?1 and the equilibrium P concentration at zero sorption (EPC₀) from 0.1 to 2.75μg g^?1. By using Langmuir co-efficients derived from P sorption experiments and soluble reactive phosphorus (SRP) concentrations measured in rivers as well as the in-shore waters of Lake Victoria, it was possible to determine the potential release of SRP into the lake by sediment from the two catchments. For the 2000 water-year, it was estimated that about 28.65 ± 0.89 (mean ± SD) and 66 ± 6.76 tons of SRP were released into Lake Victoria by sediment deposited by the Simiyu and Kagera rivers, respectively. The implications of these results to future management of cultural eutrophication in Lake Victoria are also discussed.     

Arsenic and fluoride removal by potato peel and rice husk (PPRH) ash in aqueous environments

Finding appropriate adsorbent may improve the quality of drinking water in those regions where arsenic (As) and fluoride (F^?) are present in geological formations. In this study, we evaluated the efficiency of potato peel and rice husk ash (PPRH-ash)-derived adsorbent for the removal of As and F from contaminated water. Evaluation was done in batch adsorption experiments, and the effect of pH, initial adsorbate concentration, contact time, and adsorbent dose were studied. Characteristics of adsorbents were analyzed using scanning electron micropcope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Both the Langmuir and Freundlich isotherm models fitted well for F^? and As sorption process. The maximum adsorption capacity of adsorbent for As and F^? was 2.17 μg g^?1 and 2.91 mg g^?1, respectively. The As and Fi removal was observed between pH 7 and 9. The sorption process was well explained with pseudo-second order kinetic model. Arsenic adsorption was not decreased in the presence of carbonate and sulfate. Results from this study demonstrated potential utility of this agricultural biowaste, which could be developed into a viable filtration technology for As and F^? removal in As- and F-contaminated water streams.     

黏土矿物中重金属离子的吸附规律及竞争吸附

采用等温吸附法,研究了重金属铜、铅、镉、镍在膨润土中的吸附特征,发现膨润土对铜、铅的吸附明显强于镉、镍,吸附强度大小顺序为Pb2 >Cu2 >Ni2 >Cd2 。Langmuir和Freundlich方程对这4种金属离子等温吸附的拟合均呈极显著关系。Pb2 、Cd2 、Ni2 分别与Cu2 的双组分竞争吸附表明,黏土矿物对4种离子具有"选择性吸附"。在Pb2 、Ni2 、Cd2 的存在条件下,黏土矿物对Cu2 的吸附产生不同程度的下降;100mg/LCu2 对Pb2 的影响不大,但可完全抑制Ni2 、Cd2 的吸附。建立了IAS和LCA模型来预测Pb2 与Cu2 的双组分竞争吸附,并对LCA模型进行修正,提出了更符合实际情况的竞争吸附模型。文章最后用LCA修正模型对Pb2 与Cu2 的双组分竞争吸附进行了模拟。     

Biosorption of Lead from Industrial Wastewater Using Chrysophyllum albidum Seed Shell

The shell of the seed of Chrysophyllum albidum carbon was used to adsorb lead (Pb) from aqueous solution, the sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration, and particle size on adsorption were also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The first-order rate equation by Lagergren was tested on the kinetic data and the adsorption process followed first-order rate kinetics. Isotherm data were analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms; the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 72.1 mg Pb (II) g^{- 1} at initial pH of 5.0 at 30°C for the particle size of 1.00 to 1.25 mm with the use of 2.0 g/100 ml adsorbent mass. The structural features of the adsorbent were characterized by Fourier transform infrared (FTIR) spectrometry; the presence of hydroxyl, carbonyl, amide, and phosphate groups confirms the potential mechanism adsorption of the adsorbent. This readily available adsorbent is efficient in the uptake of Pb (II) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

Preparation and characterization of silica gel/chitosan composite for the removal of Cu(II) and Pb(II)

Silica gel/chitosan composite (SiCS) was prepared via., sol-gel method by mixing silica gel and chitosan and cross-linked with bifunctional cross-linker glutaraldhyde. The SiCS composite was characterized using FT-IR, SEM-EDAX, XRD and BET methods. The sorption of copper and lead ions onto SiCS has been investigated. The SiCS composite was found to have excellent metal sorption capacity than the silica gel (Si) and chitosan (CS). The sorption experiments were carried out in batch mode to optimize various parameters viz., contact time, pH, initial metal ion concentration, co-ions and temperature that influence the sorption. Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models were applied to describe isotherm constants. Equilibrium data agreed well with the Freundlich isotherm model. Thermodynamic studies revealed that the nature of sorption is spontaneous and endothermic. The SiCS removes metals by means of adsorption and complexation. Sorption capacity of SiCS is compared with other sorbents which suggest that this composite was useful for removing copper and lead from aqueous solution.     

Effect of Dissolved Organic Matter from Wheat Straw or Swine Manure on the Cu Adsorption in Three Chinese Soils

Batch equilibration experiments were conducted to evaluate the effects of dissolved organic matter (DOM) from wheat straw (DOMw) and swine manure (DOMs) on copper (Cu) adsorption and behavior in Haplic Phaeozems, Haplic Acrisol, and Eutric Fluvisol in China. Results showed that the Cu adsorption isotherms were well fitted with both Langmuir and Freundlich equations. The Cu maximum potential adsorption capacity of the three soils followed the order of Eutric Fluvisol > Haplic Phaeozems > Haplic Acrisol. DOMw and DOMs increased the Cu adsorption capacity in Haplic Phaeozems and Haplic Acrisol, and the promoting role of DOMs on Cu adsorption was obviously higher than that of DOMw. Increasing DOM concentration of DOMw and DOMs promoted the Cu adsorption in Haplic Phaeozems and Haplic Acrisol. However, this promoting effect weakened with increasing DOM concentration. Moreover, DOMw and DOMs inhibited the Cu adsorption in Eutric Fluvisol, and this inhibitory effect significantly increased with increasing DOM concentration. The results may be used to assess the potential environmental contamination of the studied soils and to control the application of organic fertilizers.     

Copper accumulation byAspergillus awamori

Aspergillus awamori accumulated Cu2+ from aqueous solutions. The level of copper uptake was dependent on the ambient metal concentration. The process consisted of two phases: a fast initial phase and a slower secondary phase. Chelation of these ions occurs by chemical, equilibrated and saturable mechanism, following the mathematical models of Langmuir and Freundlich, with better performance on the Langmuir model. Data transformation allowed us to calculate the kinetic constants of the sorption reaction.     

Influence of hydrogen cations on kinetics and equilibria of heavy-metal sorption by algae—sorption of copper cations by the alga Palmaria palmata (Linnaeus) Weber & Mohr (Rhodophyta)

The influence of hydrogen cations on kinetics and equilibria of sorption of copper cations by the marine alga Palmaria palmata (Linnaeus) Weber & Mohr was studied under static conditions. The competitive effect of the H⁺ cations is described, which influenced the uncertainty of evaluation of the alga sorption capacity. Under static conditions, the variation of the Cu²⁺/H⁺ concentration ratio during sorption was found nonmonotonic. The Langmuir isotherm model was used to determine the sorption capacity of the alga, namely 12.4 mg g^?1 of dry algae mass. A similar value was determined from the kinetic parameters of the ionic exchange which is considered a pseudo-second-order chemical reaction. The consistent results indicated that the mathematical models used correctly described the equilibria and kinetics of the ionic exchange between algae and solutions.