Identification of potential soil adsorbent for the removal of hazardous metals from aqueous phase

The present study attempted to identify the efficient hazardous metal-removing sorbent from specific types of soil, upper and middle layer shirasu, shell fossil, tuff, akadama and kanuma soils of Japan by physico-chemical and metal (arsenic, cadmium and lead) removal characterizations. The physico-chemical characteristics of soil were evaluated using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy techniques, whereas metal removal properties of soil were characterized by analyzing removal capacity and sorption kinetics of potential metal-removing soils. The chemical characteristics revealed that all soils are prevalently constituted of silicon dioxide (21.83–78.58 %), aluminum oxide (4.13–38 %) and ferrous oxide (0.835–7.7 %), whereas calcium oxide showed the highest percentage (65.36 %) followed by silicon dioxide (21.83 %) in tuff soil. The results demonstrated that arsenic removal efficiency was higher in elevated aluminum oxide-containing akadama (0.00452 mg/L/g/h) and kanuma (0.00225 mg/L/g/h) soils, whereas cadmium (0.00634 mg/L/g/h) and lead (0.00693 mg/L/g/h) removal efficiencies were maximum in elevated calcium oxide-containing tuff soil. Physico-chemical sorption and ion exchange processes are the metal removal mechanisms. The critical appraisal of three metal removal data also clearly revealed cadmium > lead > arsenic order of removal efficiency in different soils, except in tuff and akadama soils followed by lead > cadmium > arsenic. It clearly signified that each type of soil had a specific metal adsorption affinity which was regulated by the specific chemical composition. It may be concluded that akadama would be potential arsenic-removing and tuff would be efficient cadmium and lead-removing soil sorbents.     

Adsorption of heavy metals in glacial till soil

The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI), trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero charge (pH _PZC ) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II).     

Quaternary sediments and their weathering history in northcentral Missouri

Quaternary strata in northcentral Missouri were deposited prior to, during, and subsequent to glaciation of the area. Major depositional units are separated by buried soils. The lower Quaternary Whippoorwill formation is derived from local bedrock and has the intensely weathered New Florence soil developed in it. The pre-Illinoian McCredie formation, primarily till, is derived from distant shield and local cratonic rocks. The moderately weathered Kingdom City soil within the formation suggests that an intcrglacial separated two ice advances. The lllinoian Lovcland and Wisconsinan Peoria Loesses are derived from Missouri River outwash. Since glaciation, the welded Yarmouth-Sangamon Soil has developed in till and in lllinoian loess on stable sites but middle and late Sangamon Soils have developed on erosional surfaces. Holocene soils are developed in Wisconsinan loess and alluvium-colluvium.     

Competitive adsorption of Cd,Cu, Pb and Zn by different soils of Eastern China

Simultaneous competitive adsorption behavior of Cd, Cu, Pb and Zn onto nine soils with a wide physical–chemical characteristics from Eastern China was measured in batch experiments to assess the mobility and retention of these metals in soils. In the competitive adsorption system, adsorption isotherms for these metals on the soils exhibited significant differences in shape and in the amount adsorbed. As the applied concentration increased, Cu and Pb adsorption increased, while Cd and Zn adsorption decreased. Competition among heavy metals is very strong in acid soils with lower capacity to adsorb metal cations. Distribution coefficients (K _dmedium) for each metal and soil were calculated. The highest K _dmedium value was found for Pb and followed by Cu. However, low K _dmedium values were shown for Zn and Cd. On the basis of the K _dmedium values, the selectivity sequence of the metal adsorption is Pb > Cu > Zn > Cd and Pb > Cu > Cd > Zn. The adsorption sequence of nine soils was deduced from the joint distribution coefficients (K _dΣmedium). This indicated that acid soils with low pH value had lower adsorption capacity for heavy metals, resulting in much higher risk of heavy metal pollution. The sum of adsorbed heavy metals on the soils could well described using the Langmuir equation. The maximum adsorption capacity (Q _m) of soils ranged from 32.57 to 90.09 mmol kg⁻¹. Highly significant positive correlations were found between the K _dΣmedium and Q _m of the metals and pH value and cation exchange capacity (CEC) of soil, suggesting that soil pH and CEC were key factors controlling the solubility and mobility of the metals in soils.     

Sorption and distribution of adsorbed metals in three soils of India

The mobility and bioavailability of heavy metals depends on the metal retention capacity of soil and also on the geochemical phases with which metals are associated. Laboratory batch experiments were carried out to study the sorption and distribution of Cd, Ni and Pb in 3 soils differing in their physicochemical properties from India: Oxyaquic Haplustalf (SL1), Typic Haplustalf (SL2) and Typic Haplustert (SL3). The heavy metal adsorption was studied by isotherms and the distribution coefficient (K_D) for each metal was obtained from the linear regressions of the concentration of metal remaining in equilibrium solution and the amount adsorbed. In general, the sorption capacity for all the metals decreased in the order: SL3>SL2>SL1. Among metals, the sorption capacity in all the soils decreased in the order: Pb>>Ni>Cd. Distribution of sorbed metals at various equilibrating concentrations was studied by sequential extraction. Results showed significant differences in the distribution of metals in these soils. At higher additions (such as 200 μM l⁻¹) most of the metals were extracted in their more mobile fractions, exchangeable and/or inorganic in contrast to their original partitioning in soils, where they were preferentially associated with the less mobile residual fraction. Largest percentages of metals extracted in the exchangeable fraction corresponded to those soil–metal systems with smaller K_D values, e.g. Cd, Ni and Pb in SL1 and Cd and Ni in SL2. In neutral and alkaline soils (SL2, pH=7.1, and SL3, pH=8.6) Pb was predominantly extracted from the inorganic fractions and this corresponded to higher K_D values for Pb in these soils. The predominance of metals associated with the exchangeable fraction together with low K_D values indicates higher mobility of metals retained in the acidic soil (SL1, pH=5.2) compared with the others.     

岩溶区典型土壤对Cd2+的吸附特性

文章采用有序批试验,就岩溶区两种典型石灰土（棕色、黑色石灰土）对Cd2+的吸附行为进行研究。试验结果表明:石灰土对重金属Cd2+具有较强的吸附能力（平均吸附率范围89.84~98.84）,黑色石灰土的吸附能力高于棕色石灰土,吸附量随平衡浓度的增加而增大;Langmuir和Freundlich方程均能很好地描述两种石灰土对Cd2+的等温吸附过程,Freundlich方程拟合最优;两种石灰土吸附镉的动力学特征相似,吸附过程可分为快速反应、慢速反应和吸附平衡3个阶段,棕色石灰土对Cd2+吸附动力学的最优模型为Elovich方程和双常数方程（R>0.9）,黑色石灰土仅在Cd2+初始浓度为100 mg/L条件下,Elovich方程、双常数方程和W-M方程的模拟达到较显著水平（R>0.8）;有机质、碳酸钙含量及CEC值是影响石灰土对Cd2+吸附能力的主控因素,铁、铝、硅氧化物含量对Cd2+吸附影响不大;综合热力学、动力学及影响因素分析认为石灰土对Cd2+吸附机理包括土壤颗粒表面官能团的专性吸附及不均匀粒内扩散、静电作用等非专性吸附过程。      

Sorption of surfactants and personal care products in Indian soils

Sorption of three surfactants and personal care products in four types of commonly occurring Indian soils was extensively studied. The soils used in the study were red soil, clay soil, compost soil and sandy soil as classified by American Society for Testing and Materials (ASTM). The three surfactants used in the study were representative of cationic, non-ionic and anionic surfactant groups. The sorption of surfactants followed the descending order: sodium dodecyl sulphate (SDS) > trimethyl amine (TMA) > propylene glycol (PG). The maximum adsorption capacity (Q_max) was obtained in compost soil (28.6 mg/g for SDS; 9.4 mg/g for TMA and 4 mg/g for PG). The rate of adsorption was the maximum in compost soil followed by clay and red soils, and minimum for sandy soils. It is found that the Freundlich model fits the isotherm data better than the Langmuir model. Freundlich coefficient (K _f) increased as the organic content of soils increased. Desorption of target pollutants in tap water was 20–50% whereas acid desorbs 40–90% of target pollutants from soil matrix. It was also found that the adsorption and desorption were significantly affected by the presence of clay and organic matter. The results also indicate that surfactants and personal care products, especially TMA and PG, are highly mobile in sandy soil followed by red soil. Therefore, immobilization of target pollutants is most economical and effective in compost and clayey soils whereas for other type of soils the combination of physiochemical and biological process will be effective option for remediation.     

Single element and competitive sorption of copper, zinc and lead onto a Luvisol profile

The sorption parameters of Cu, Zn and Pb are related to the composition of the different genetic horizons of a Luvisol profile in batch sorption experiments. The affinities of metals towards the soil samples from different horizons followed the same sequence, e.g. Pb≥C>>Zn. By far the highest metal retention was found in the C_k horizon due to the alkaline conditions. It is followed by the A horizon with its high organic matter content, while the lowest sorption capacity was found in the Bt horizon. In the horizons free of carbonate, primarily Pb and Cu were immobilized. The studied soil can be characterized by high amount of organic matter, clay accumulation horizon, as well as calcareous subsoil. This kind of profile development makes soils able to immobilize a significant metal pollution.     

Interactions between Cd,Cu, Pb,and Zn and four different mine soils

The chemical associations of Cd, Cu, Pb, and Zn in four mine soil samples from the Amizour-Bejaia Pb/Zn mine (Algeria) have been investigated by a five-step sequential extraction procedure. Although Cd preferentially binds to carbonates, Cu, Pb, and Zn are mainly associated with the organic and reducible fractions. Batch adsorption experiments with either mono- or multi-metallic solutions are described with the Freundlich isotherm model. Whatever the nature of the soil sample, the sorption behavior for each given metal except Pb is very similar, indicating that the binding sites at the soil surface are progressively occupied by the metal from the solution. On each soil sample, the decreasing order of sorption can be established as Pb >> Cu > Cd > Zn. When the four metals are simultaneously applied to each soil sample, their specific behavior is strongly affected by their interactions and/or competition for the available surface sites: we generally observed isotherm curves with a slight maximum before the plateau at higher solution concentration. Although Cu is only slightly affected by the other metals, in the case of Pb, Cd, and Zn, the sorbed amounts strongly decreased.     

Phosphorus transport in shallow groundwater in peri-urban Kampala, Uganda: results from field and laboratory measurements

To understand Phosphorus (P) sources and transport processes in the subsurface in Bwaise III Parish, Kampala, P attenuation and adsorption capacities of soils were studied in situ and from laboratory measurements. Relationships between sorption parameters and soil matrix properties, rates and mechanism of the adsorption process and soil P fractions were also investigated. P was generally higher in the wet than the dry season, but for both seasons, the maximum was 5 mgP/l. P transport mechanisms appeared to be a combination of adsorption, precipitation, leaching from the soil media and by colloids with the latter two playing an important role in the wet season. The sorption process comprised two phases with the first stage rate constants being about fourfold those of the second stage. The Langmuir isotherm described the sorption data well (R ² ≥ 0.95) with the second soil layer exhibiting the highest sorption maximum (C _max) (average value 0.6 ± 0.17 mgP/gDW). The best prediction of C _max had organic carbon, Ca, available P and soil pH. Residual P consisting mostly of organics was the main fraction in all the layers followed by inorganic HCl-P and NaOH-P in the top and middle layers, respectively. Loosely bound P (NH₄Cl-P) was the least fraction (<0.4% of total P) in all layers indicating the high binding capacity of P by the soils. The study results suggest that P dynamics is related to Ca, Fe and organic carbon content of the soils.     

Engineering-geological mapping of tropical soils for land-use planning and geotechnical purposes: A case study from Jamaica, West Indies

An area of a Tertiary and Cretaceous deposits, 100–310 m above sea level and on predominant 20–45°, highly dissected, concave slopes was investigated to assess its geotechnical characteristics and land use planning implications. Lithologies include turbidites, fluvial conglomerates, breccias, sandstones, mudrocks, carbonates, granodiorite, acid dykes, chloritized and epidotized volcanics, andesite and Holocene fluvial deposits. Bedrock is highly fractured and sheared, hydrothermally altered and highly weathered. Soils are quite variable, with a strong geological control on soil properties. Soils are generally sandy to gravely, with local silts and clays in mudrocks, within Holocene alluvium or in hydrothermally altered and sheared granodiorites. The soils are composed of 0.14–80.00% gravel; 5.36–62.50% sand, 2.33–50.55% silt, 0.17–51.50% clay, and total fine content between 2.50 and 94.50%, with natural moisture between 4 and 44% during the dry season, plastic limit between 6 and 35%, liquid limit between 19 and 83% and plasticity index between 1 and 59%. Sandy soils have residual friction angles between 19 and 39°, PI values less than 35% with cohesion between 1.00 and 5.27 KN/m² for cohesive samples. ASTM classification of soils include soil groups GC, GM, GW, GP, SP, SM, SC, SM, SC, ML, CL and CH.

Based on the characteristics of the terrain, the geotechnical and land use planning problems include high landslide frequency and susceptibility, soil erosion, fluvial and reservoir sedimentation, high debris flow hazard, cut slope failures, potentially expansive clays and silts, seepage erosion and soil piping, differential settlement in interlayered competent and incompetent lithologies, high solution erosion and potential subsidence over limestones, waste water disposal problems and groundwater pollution and seismic induced settlement and ground failures. These phenomena suggest that systematic site investigations should be conducted prior to the utilization of these areas for construction and development in order to minimize the deleterious effects resulting from ground failure.     

Efficacy of Fine-Grained Soil as Landfill Liner Material for Containment of Chrome Tannery Sludge

This paper evaluates the potential use of a fine-grained soil obtained from a site in West Bengal, India, as a suitable landfill liner material for the containment of hexavalent chromium from tanning waste sludge. The physico-chemical properties of the soil were determined. The soil adsorption affinity for hexavalent chromium was also assessed through adsorption batch and breakthrough column tests. The zero point charge (pH_zpc) of the soil was found to be 7.3. The batch kinetics and column tests results indicated that the soil liner possesses a relatively good hexavalent chromium adsorption capacity at natural or slightly alkaline condition. The adsorption results showed that the hexavalent chromium uptake by the soil follows both Langmuir and Freundlich adsorption isotherms. This study also illustrated that the hexavalent chromium breakthrough curve in the column experiment reached equilibrium concentration after 3.5 pore volumes (900 h). Overall, this study showed that the fine-grained soil has the potential for usage as a landfill liner or as a component of a landfill barrier system to prevent chromium contamination from the tannery waste disposal.     

Toluene sorption behavior on soil organic matter and its composition using three typical soils in China

The effect of soil organic matter (SOM) content and composition on sorption behavior of toluene for fluvo-aquic, red and black soils in China was investigated in batch experiments. Tested SOM was fractionated into two primary sorptive domains (‘soft’ and ‘hard’) to explain the dependence of sorption behavior on SOM composition. All the tested soils exhibited similar sorption kinetics and nonlinear sorption isotherms. Soils with high SOM content possessed a high sorptive capacity. Clay minerals also contributed to the sorptive capacity, especially for fluvo-aquic and red soils with low SOM content. In comparison, after removing most ‘soft’ SOM fraction from soils through hydrogen peroxide treatment, the residual ‘hard’ SOM fraction of three soil samples exhibited a slower sorption rate and a less sorption capacity compared to the untreated soil samples. The nonlinear degree of sorption was positively correlated with the content of ‘hard’ SOM for all soil samples. This is explained by the combined effect of SOM content and the composition on toluene sorption rates, sorption capacity and nonlinear degree of sorption of three typical soils in China.     

水稻土中重金属元素Cd、Pb的竞争吸附 ——以长株潭地区水稻土为例

对中国南方的3个水稻土样品进行了Cd、Pb单一离子和混合离子吸附特点的研究。结果表明,3个水稻土样品中Cd、Pb的吸附特点都相似,Langmuir等温方程可很好地描述Cd、Pb的吸附等温线。3个土壤样品中,有较高pH值和较低有机物、CEC浓度、粘土含量、高岭石含量的2个土壤样品对Cd、Pb有较大的吸附量,且其等温吸附拟合的最大吸附量(B)也较大。在两组分混合溶液中,尽管共存离子的存在影响了土壤对单一离子的吸附,同时土壤对Cd的吸附在一定程度上受影响的程度大,但3个土壤样品都表现出对Pb有强的吸附能力。在3个土壤样品中,Langmuir等温方程中Pb的健合能常数(K)都大于Cd的健合能常数(K),混合溶液中的K值高于单一溶液的K值,表明2种金属离子对吸附位点的竞争提高了特定吸附位点的保持力,使金属离子在土壤中特定位点的吸附更加坚固。     

Evaluation of contaminants retention in soils from Viamão District, Rio Grande do Sul State, Brazil

Adsorption is one of the most significant processes in the mobility of soluble pollutants in soils. The aim of this work is to characterize and evaluate the adsorption capacity of soils from Viamão District, Brazil. The studied ions were lead_total, copper_total, sulfate, phosphate, and potassium. The soils were mapped by remote sensing and characterized by granulometrical and mineralogical techniques. The adsorption tests were made by the contact of soil samples with aqueous solutions. The soils adsorption capacity presented the following trend: Pb_total>Cu_total≈PO ₄ ³⁻ >K⁺ ≈SO ₄ ²⁺ . Adsorption in the soils is strongly influenced by clay content. The adsorption of phosphate, copper, and lead was accentuated by the presence of organic matter. Phosphate adsorption was controlled by oxides and organic matter. Both potassium and sulfate showed insignificant adsorption in the studied soils.     

Phosphate sorption desorption characteristics of some ferruginous soils of tropical region in Eastern India

Phosphate sorption and desorption experiments were conducted with four ferruginous soils (alfisols) of Eastern India, in view of the low native phosphate concentrations in tropical Indian soils. From the P-isotherm curve, standard P requirement (SPR) of the soils was determined. Phosphate sorption data were fitted to both Langmuir and Freundlich equations and mean sorption maximum values obtained for the different soil series were in the decreasing order as Matimahal > Anandapur > Mrigindih > Kashipur. The fraction of added P sorbed followed the same trend as SPR, P sorption maximum (P_max), phosphate affinity constant (K), maximum phosphate buffering capacity (MPBC), Freundlich constant K′ and phosphate desorption values. Phosphate sorption maximum was significantly correlated with MPBC, Freundlich 1/n, SPR, clay and different forms of Fe and Al. The value of K (bonding energy) was significantly correlated with MPBC, Freundlich K′ and pyrophosphate extractable Fe and Al. The MPBC was significantly correlated with Freundlich K′, Freundlich constant 1/n, clay, oxalate and dithionite extractable, amorphous and crystalline form of Fe and Al. Freundlich K′ was significantly correlated with Freundlich 1/n, pH_water, clay, dithionite extractable and crystalline form of Fe and Al. The results suggested that the soils having higher amount of extractable and reactive Fe and Al shared higher P sorbtion capacity and such soils may need higher levels of P application     

Citrate sorption and biodegradation in acid soils with implications for aluminum rhizotoxicity

Citrate and other organic acids play an important role in the rhizosphere and pedogenic processes. Although secreting citrate from roots in response to Al and heavy metal stress has been recognized as a central mechanism for plants to avoid toxicity, the efficiency of root citrate on metal detoxification is still contradictory in acid soil with abundant oxide minerals that serve as a potential sorption site for citrate. The objective of this study was to investigate sorption and biodegradation of citrate in subtropical acid soils with different mineralogical properties. A batch experiment was conducted to assess the possible fates (adsorption and biodegradation) of citrate in the three acid soils (Cecil, Creedmoor and Norfolk) under microbial-active and inactive conditions. Citrate adsorption isotherms for all soils were adequately described by the Freundlich equation with the R² value being over 0.90. The Cecil soil had the highest affinity for citrate adsorption among the soils with 99% adsorption observed throughout the citrate concentration range, which was due primarily to the abundant Al and Fe oxides. Citrate sorption to the mineral phase significantly reduced its biodegradation by 56%, 65% and 99% for the Creedmoor, Norfolk and Cecil soils, respectively. The results suggest the efficiency of rhizosphere processes for Al detoxification by root-secreted citrate would be significantly reduced in acid soil with abundant Al and Fe oxides.     

Distribution and sorption of potentially toxic metals in four forest soils from Hungary

Metals of natural and anthropogenic origin behave differently in soils mostly due to their different mobility. In this study, sequential extractions and batch sorption experiments were performed to relate the fractionation of native Ni, Cu, Zn and Pb to the sorption properties of added metals in four soils with contrasting physiochemical characteristics. A significant effect due to sample composition on both the mobility and sorption characteristics of these metals was found. The efficiency of soil components in metal immobilization was in the order of carbonate > organic matter > swelling clay minerals. The partitioning of native metals together with the information gained through the sorption isotherms allows a deeper insight on the fate and behavior of metals in soils with various compositions.     

Sorption behaviour of pentachlorophenol in sub-Saharan tropical soils: soil types sorption dynamics

In order to predict exposure risks as well as appropriate remediation strategies for pesticides in soils, knowledge of pesticides sorption processes onto various representative soils is vital. Hence, laboratory batch experiments were carried out to study sorption of a pesticide, pentachlorophenol (PCP), on five soils obtained from different sub-Saharan agro-ecological zones (AEZs) in order to understand sorption equilibrium, kinetics, and thermodynamics. Experimental data showed that sorption equilibrium was attained within 24 h. The fitting of kinetic results and equilibrium data to different models suggested partly surface adsorption and partly partitioning of PCP within voids of the various soil components. Sorption was mainly attributed to sharing or exchange of valence electrons between negatively charged PCP molecules and positively charged soil sorption sites. The sorption process was spontaneous and accompanied by decreased entropy, but was pH and temperature dependent, reducing with increase in pH and temperature. The various soils’ PCP sorption capacities were directly proportional to their cation exchange capacities. The low PCP sorption observed in these soils suggested high risk of PCP being present in soil water solution, especially at higher temperatures, which can lead to contamination of the aquifer. This risk may be higher for soils obtained from AEZs with warmer natural temperatures.     

水稻土中重金属元素Cd、Pb的竞争吸附——以长株潭地区水稻土为例

对中国南方的3个水稻土样品进行了Cd、Pb单一离子和混合离子吸附特点的研究。结果表明,3个水稻土样品中Cd、Pb的吸附特点都相似,Langmuir等温方程可很好地描述Cd、Pb的吸附等温线。3个土壤样品中,有较高pH值和较低有机物、CEC浓度、粘土含量、高岭石含量的2个土壤样品对Cd、Pb有较大的吸附量,且其等温吸附拟合的最大吸附量（B）也较大。在两组分混合溶液中,尽管共存离子的存在影响了土壤对单一离子的吸附,同时土壤对Cd的吸附在一定程度上受影响的程度大,但3个土壤样品都表现出对Pb有强的吸附能力。在3个土壤样品中,Langmuir等温方程中Pb的健合能常数（K）都大于Cd的健合能常数（K）,混合溶液中的K值高于单一溶液的K值,表明2种金属离子对吸附位点的竞争提高了特定吸附位点的保持力,使金属离子在土壤中特定位点的吸附更加坚固。