Sorption Potential Research Articles

Experimental Modeling of Platinum Biomineralization by Microscopic Fungi Isolated from a Lignite Deposit

Based on scanning electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy, it was shown that platinum sorption by the biomass of microscopic fungi occurs in several stages. Incipient interaction involves physical and chemical sorption and is followed by the reduction of adsorbed platinum ions to a zero-valence state at the expense of metabolic products of microorganisms and eventual aggregation of zero-valence particles to nanometer-sized forms. Model experiments revealed a high platinum sorption potential of the physiologically active biomass of microscopic fungi and their cell envelopes (chitin).

Pyrogenic Materials-Induced Immobilization of Eu in Aquatic and Soil Systems: Comparative Study

Pyrogenic materials produced from various input materials and with valuable characteristics such as high porosity, extensive surface area, and mineral composition represent alternative to traditional carbon-based materials in area of contaminant immobilization, aqueous solutions purification, and soil remediation. Intensification of industry and technological processes brings increased use of lanthanides and thus potential risk of lanthanide penetration into soil and aquatic systems. This study examined the roles of three different pyrogenic materials: microcrystalline cellulose-derived pyrogenic materials (MCPM), organic cotton-derived pyrogenic material (OCPM), and sewage sludge-derived pyrogenic material (SSPM) produced in the process of slow pyrolysis at 430 °C in N2 atmosphere as potential Eu immobilization and sorption materials. Produced materials were characterized by determination of wide range physicochemical properties via elemental analysis, SEM, FT-IR, and sorption potential for Eu in batch sorption experiments. The obtained data confirmed that sorption separation of Eu by OCPM, MCPM, and SSPM from aqueous solution is relatively rapid process with reached equilibrium at 24 h. Batch equilibrium experiments revealed maximum sorption capacities 0.602 mg g−1 for MCPM, 1.761 mg g−1 for OCPM, and 2.586 mg g−1 for SSPM. The presence of co-ions such as Al in system reduced sorption potential about more than 50% for all three studied materials. Column leaching test with artificially contaminated soil and 5% (w/w) amendments of pyrogenic materials showed significant retention ability of MCPM, OCPM, and SSPM for mobile Eu forms compared to control soil. Pyrolysis production of pyrogenic materials and their applications as an effective immobilization and separation tools for wide range of xenobiotics can be innovative method in environmental management and waste assessment.

Possible use of synthesized nano silica functionalized by Prussian blue as sorbent for removal of certain radionuclides from liquid radioactive waste

The Prussian blue functionalized SiO2 (nano-material of SiO2-Fe-CN) was successfully prepared using a novel and simple preparation route. The SiO2 nanoparticles were functionalized by amino group by refluxing with (3-Aminopropyl) trimethoxysilane, iron (III) immobilized the modified nanoparticles through interaction with the amino group, finally, SiO2-Fe-CN nanomaterial produced as a result of potassium ferrocyanide addition. SEM, FTIR and XRD techniques were used for detecting the morphology, particle size, different functional groups and the crystal structure of the prepared nano-materials. The sorption potential of nano-material of SiO2-Fe-CN towards cationic and anionic radioisotopes from aqueous and HNO3 solutions were tested using carrier free method. The experimental results showed that nano-material of SiO2-Fe-CN have high effective retention and recovery for 134Cs, 60Co and 99Mo from nuclear liquid waste. Moreover, sorption of 90Sr/90Y is insignificant using SiO2-Fe-CN nano adsorbent material. It is a promising and efficient nano adsorbent that could be used for upscaling design and application on liquid radioactive waste treatment facility.

Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products

Because of their large surface area and reactivity, nanometric-size soil mineral phases have a high potential for soil organic matter stabilization, contaminant sorption or soil aggregation. In the literature, Fe and Al phases have been the main targets of batch-synthesized nanomineral studies while nano-aluminosilicates (Al and Si phases) have been mainly studied in Andic soils. In the present work, we synthesized secondary nanophases of Fe, Al and Si. To simulate a system as close as possible to soil conditions, we conducted laboratory simulations of the processes of (1) biotite alteration in acidic conditions producing a Al Si Fe Mg K leachate solution and (2) the following neoformation of secondary nanophases by titrating the leachate solution to pH 4.2, 5 and 7. The morphology of the nanophases, their size, crystallinity and chemistry were characterized by TEM-EDX on single particles and their local atomic structure by EXAFS (Extended X-ray Absorption Fine Structure) at the Fe absorption K-edge. The main nanophases formed were amorphous particles 10–60 nm in size whose composition (dominated by Fe and Si) was strongly controlled by the pH conditions at the end of the titration. At pH 4.2 and pH 7, the structure of the nanophases was dominated by the polymerization of Fe, which was hindered by Al, Si, Mg and K. Conversely, at pH 5, the polymerization of Fe was counteracted by precipitation of high amounts of Si. The synthetized nanophases were estimated to be rather analogous to nanophases formed in natural biotite-bearing soils. Because of their small size and potential high surface reactivity, the adsorption capacities of these nanophases with respect to the OM should be revisited in the framework of soil C storage.

Preliminary evaluation of the application of carbon nanotubes as potential adsorbents for the elimination of selected anticancer drugs from water matrices

The presence of anticancer drugs in the environment raises a major concern due to their potentially negative impact on living organisms, as they cause, inter alia, teratogenic, mutagenic, carcinogenic effects on growing cells. The main source of these pharmaceuticals in the environment is the ineffectively treated wastewaters, hence the efficient methods for their removal are required. In this study, we have evaluated for the first time the applicability of different Multi-Walled Carbon Nanotubes (MWCNTs) as alternative adsorbents for the removal of three popular anticancer drugs from water matrices, which are detected in waste/hospital waters at the concentrations even up to μg L−1: cyclophosphamide (CP), ifosfamide (IF) and 5-fluorouracil (5-FU). It was observed that adsorption equilibrium time was reached after 20 min for each compound and CNTs. Moreover, CP has the highest sorption potential (Kd up to 1597 L kg−1) for all CNTs and CNTs with the highest surface area have the greatest adsorption capacity. Isotherms were fitted best to the Freundlich model. Significant influence of pH in the range 4–9 and ionic strength was not observed what may indicate that adsorption is not dependent on fluctuation of basic environmental conditions.

Removal of Zinc onto Several Adsorbents Derived from Waste Activated Sludge of Crumb Rubber Industry (CRI-WAS)

Waste activated sludge of crumb rubber industry (CRI-WAS) is discarded as waste from wastewater treatment processing. Therefore it is necessary to develop and innovate to convert the material becomes valuables and expected to be an economical adsorbent for metal ion remediation from wastewater. The ability of three types of adsorbents prepared from CRI-WAS for the removal of Zn(II) from aqueous solutions has been investigated. The XRF, BET, SEM-EDX, and FTIR analysis were conducted to characterize the PS (pure sludge), WS (washed sludge) and P600 (pyrolysis at 6000C) CRI-WAS types of adsorbents. In the batch system, experimental parameters were investigated, including solution pH, contact time, and adsorbent dose. The data were analyzed by analysis of variance (ANOVA) and a further test Duncan's New Multiple Range Test (DNMRT) at the 5% significance level. The results reveal that all types of adsorbent exhibited good sorption potential at pH 5.0. The P600 has largest adsorption capacity. The maximum adsorption capacity of the adsorbent for Zn(II) was found to be 10.276 mg g-1, 11.042 mg g-1 and 64.169 mg g-1 for PS, WS and P600 CRI-WAS types of adsorbents respectively. The results showed that the adsorption isotherm data were fitted well by the Langmuir isotherm.

Sorption and bioaccumulation behavior of multi-class hydrophobic organic contaminants in a tropical marine food web

While numerous studies have demonstrated the environmental behavior of legacy persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), information regarding sorption and bioaccumulation potential of other widely used organic chemicals such as halogenated flame retardants (HFRs) is limited. This study involved a comprehensive field investigation of multi-class hydrophobic organic contaminants (HOCs) in environmental media and fish in Singapore Strait, an important tropical maritime strait in Southeast Asia. In total, 90 HOCs were analyzed, including HFRs, synthetic musks, PCBs, OCPs, as well as triclosan and methyl triclosan. The results show that the organic carbon normalized sediment-seawater distribution ratios (CSED/CWD) of the studied compounds are comparable to the organic carbon-water partition coefficients (KOC), over a log KOC range of approximately 4–11. The observed species-specific bioaccumulation factors (BAFs), biota-sediment accumulation factors (BSAFs), organism-environment media fugacity ratios (fFISH/fWD and fFISH/fSED) and trophic magnification factors (TMFs) indicate that legacy POPs and PBDE 47 show bioaccumulation behavior in this tropical marine ecosystem, while triclosan, tonalide, dodecachlorodimethanodibenzocyclooctane stereoisomers (DDC-COs), and hexabromocyclododecanes (HBCDDs) do not. Methyl triclosan and galaxolide exhibit moderate biomagnification. Tetrabromobisphenol A (TBBPA) and 1,2-bis (2,4,6-tribromophenoxy)ethane (BTBPE) were detected in environmental media but not in any of the organisms, suggesting low bioaccumulation potential of these flame retardants. The apparently low bioaccumulation potential of the studied HFRs and synthetic musks is likely because of metabolic transformation and/or reduced bioavailability due to the hydrophobic nature of these compounds.

Solubility and water sorption of novel atraumatic restorative treatment materials: A In vitro Study

Objectives: The objective is to determine the solubility (SL) and sorption of novel atraumatic restorative treatment (ART) materials in deionized water or artificial saliva. Materials and Methods: Two compositions of newly developed ART materials were prepared. Individual compositions were prepared separately and placed in 100% humidity at ambient temperature for 24 h. Each was stored in separate vials, either 7 ml of deionized or artificial saliva at ambient temperature for 1, 7, 14, or 28 days. The sorption (S%) and SL% were then determined. Student's t-test was employed to assess the significance level of the differences observed. Results: After 1 day, the mean values for water sorption of the ART-I were 12.1% and ART-II were 16.8% in deionized water (P = 0.01). However, the mean water sorption in artificial saliva for ART-1 was 15.3% and that for ART-II was 18.5% (P = 0.05). The mean SL of ART-I and ART-II was 7.4% and 7.2%, respectively, in deionized water (P = 0.66), and in artificial saliva, it was 7.0% and 6.0%, respectively (P = 0.19). Conclusions: We conclude that water sorption potential of ART-II is more in artificial saliva and SL potential of ART-I was more in deionized water.

Valorization of waste micro-algal biomass - collected from coke oven effluent treatment plant and evaluation of sorption potential for fluoride removal.

Fluoride contamination in groundwater is now becoming a global concern. In the present study, removal of fluoride using dry biomass (DBM) of a micro-algal consortium of Chlorococcum infusionum and Leptolyngbya foveolaurum, collected from a coke-oven effluent treatment plant, Durgapur, India, has been investigated. The large volume of algal bloom in the industrial effluent has created serious disposal issues and caused severe environmental concerns. A biosorption technique has been carried out to valorize the waste algae biomass into a potential adsorbent. Response Surface Methodology (RSM) is used to model and optimize fluoride removal. Maximum fluoride removal (72%) is obtained at pH 4, 5 mg/L initial fluoride concentration, 0.5 g/L adsorbent dose (AD), and 25 °C temperature during one-factor-at-a-time (OFAT) analysis. The optimum condition of removal as specified by RSM is - initial concentration of fluoride: 30 mg/L, pH: 4.5, AD: 3.5 g/L and temperature: 30 °C. FESEM-EDX, FTIR and BET isotherm studies are done to characterize raw and fluoride treated biomass. Lagergren first order kinetic model and Freundlich isotherm model, are found to analyze best kinetic and equilibrium data, respectively. Adsorption capacity of DBM has been found to be 34.36 mg/g. The kinetics of fluoride removal have been well described by COMSOL Multiphysics.

Evaluation of nitroglycerin and cyclosporin A sorption to polyvinylchloride- and non-polyvinylchloride-based tubes in administration sets

We report the sorption evaluation method for injectable drugs administered using set tubes to evaluate the quality of the administration sets. The evaluation method using a peristaltic pump, so called pump method, was used for the kinetic sorption study. Nitroglycerin (NTG) and cyclosporin A (CSA) were selected as model drugs. The parameters of drug-diluted concentrations and flow rates were adapted to the clinically relevant values. Polyvinylchloride (PVC)- and non-PVC (PU and PO)-based tubes were cut to a fixed length of 1 m after removing the accessories in the administration sets. NTG and CSA were analyzed using high-performance liquid chromatography (HPLC) methods with ultraviolet (UV) detection. After the drug analyses, NTG and CSA sorption levels were calculated from the percentage values of the subtracted drug concentrations in samples from those in the diluted solutions. The average sorption levels and each sorption level at each sampling point were considered to compare the sorption levels in all administration set tubes. Both drugs showed high sorption levels in PVC- and PU-based administration set tubes. However, the drugs showed a minimum sorption potential of < 10% on PO-based tubes, which could be clinically acceptable. This suggests that the sorption evaluation methods for NTG and CSA could be promising standards for endorsing administration set tubes and for evaluating newly developed or designed polymeric alternatives. Additionally, PO could be an alternative and next-generation polymeric material for manufacturing administration set tubes.

Transformation of C60 fullerene aggregates suspended and weathered under realistic environmental conditions

The occurrence, fate and behaviour of carbon nanomaterials in the aquatic environment are dominated by their functionalization, association with organic material and aggregation behaviour. In particular, the degradation of fullerene aggregates in the aquatic environment is a primary influence on their mobility, sorption potential and toxicity. However, the degradation and kinetics of water suspensions of fullerenes remain poorly understood.In the present work, first, an analytical method based on liquid chromatography and high-resolution mass spectrometry (LC-HRMS) for the determination of C60 fullerene and their environmental transformation products was developed. Secondly, a series of C60 fullerene water suspensions were degraded under relevant environmental conditions, controlling the salinity, the humic substances content, the pH and the sunlight irradiation. Up to ten transformation products were tentatively identified, including epoxides and dimers with two C60 units linked via one or two adjacent furane-like rings. Fullerenols were not observed under these environmentally relevant conditions.The kinetics of generation of each transformation product were studied with and without simulated sunlight conditions. The ionic strength of the media, its pH and the humic substances content were observed to modulate the kinetics of generation.

Elucidation of mechanism involved in adsorption of Pb(II) onto lobeira fruit (Solanum lycocarpum) using Langmuir, Freundlich and Temkin isotherms

Novelty statement This manuscript entitled “Elucidation of adsorption mechanism of Pb(II) onto lobeira fruit (Solanum lycocarpum) using a Langmuir, Freundlich and Temkin isotherms” by Cleide Sandra Tavares Araujo et al. describes the sorption potential of lobeira fruit (Solanum lycocarpum) for removing Pb(II) from aqueous solution using a factorial experimental design as optimization strategy and Langmuir, Freundlich and Temkin models have been used to fit adsorption isotherms. The Solanum lycocarpum known popularly as “lobeira-do-cerrado”, wolf fruit or “jurubebao”, is a lignocellulosic typical species of the “cerrado” (kind of Brazilian savannah), with wide distribution, mainly in anthropized areas, has been little explored for adsorption studies. The optimization using a factorial design enabled the optimization of the procedure to be carried out with a reduced number of experiments, thus requiring a lower quantity of reagents and showed has advantages, such as, the low cost of sorbent, high efficiency and the minimization of chemical sludge. So allowed the adsorption of lead by lobeira fruit an inexpensive and easily available raw material may be used for different industrial applications to lower the cost of wastewater treatment and has potential applications for the removal of Pb(II) from wastewater. The sorbent is an alternative material for chemical remediation and is economic and environmental friendly.

Geotechnical and Geochemical Assessments of Shales in Anambra Basin, Southeastern Nigeria, as Landfill Liners

The use of landfills as containment for municipal solid waste management has received wide acceptance the world over. Its development in countries like Nigeria is constrained by high cost and scarcity of synthetic liners in the local markets. Exploration of the abundant locally available clay deposits in the country’s sedimentary Basins will prove economical, provided it satisfies the standard specifications for design and construction of landfill liners. This study thus evaluates the suitability of shales from three formations (Enugu, Ameki and Imo) within Anambra Basin of Southeastern Nigeria as liner materials. Geotechnical tests such as particle size distribution, Atterberg’s limits, compaction, coefficient of permeability and consolidation were performed on the shale samples. Geochemical analyses involving the inductively coupled plasma emission spectroscopy (ICPES) and cation exchange capacity (CEC) were also conducted; all employing standard methods. Based on the Unified Soil Classification System (USCS), Enugu and Imo shales contain high-plastic inorganic clay, while Ameki shales comprise low–medium-plastic inorganic clay. Coefficient of permeability result ranging from 9.12 × 10−6 to 2.14 × 10−6 cm/s indicates an increase above the standard specification. Expectedly, the cation exchange capacity (CEC), compressibility and plasticity index of the shales are positively related suggesting strong influence of the geotechnical properties on their sorption potentials. Overall assessment revealed that the high hydraulic conductivity and swelling potentials of the shales are not suitable for natural clay liners. Nevertheless, Enugu and Imo shales can further be stabilized chemically to the desired hydraulic conductivity of liners considering other suitable geotechnical properties and their CECs.

Pore characteristics of Damodar valley shale and their effect on gas storage potential

The current global interest in fine grained sedimentary shale rock is driven by its ability to store gas in the pore spaces in them. The current study focuses on the understanding of the gas storage capacity of less explored Damodar Valley shales of India, in light of pore characteristics of organic matter and clay minerals. In this study, four samples were collected from different parts of Damodar valley basin and their geochemical composition, pore structure and adsorption capacity were investigated by XRD studies, rock-eval analyses, low-pressure N2-CO2 adsorption analyses and high-pressure methane adsorption experiment. The samples were also studied to know their hydrocarbon potential. The relationship between mineralogy, organic matter, and pore-structure was analyzed and finally, their effect on methane sorption capacity was discussed. The shale samples are found to be clay rich. The average clay content of the shale samples is 50.69% and average quartz content is 31.65%. Presence of excellent TOC content (4.8%–37.36%) with a predominance of type III organic matter and Tmax varying from 440 °C to 465 °C suggests a very good to excellent hydrocarbon generation potential in all the samples. The correlation between the TOC and VL was found to be positive indicating a positive influence of organic matter on methane sorption capacity of the studied samples. However, a lack of correlation between total clay and CH4-VL indicates that the role of clay minerals on methane sorption behavior of these shales are inconclusive. A positive correlation between CO2 micropore volume, CH4-VL and TOC suggest microporous nature of organic matter within the shale samples and their positive control on methane sorption potential. The negative correlation of clay mineral with CO2 micropore volume suggests a lack of microporosity in the clay minerals of the collected shale samples. It was also observed that thermally mature shale samples have higher micropore volume and surface area, and are prone to higher methane sorption capacity compared to that of less mature shales.

Sorption of Pb(II), Cu(II), Fe(II) and Cr(VI) metal ions onto cross-linked graft copolymers of chitosan with binary vinyl monomer mixtures

Novel adsorbents for sorption of Pb(II), Cu(II), Fe(II) and Cr(VI) metal ions from waste water were synthesized by simultaneous cross-linking and graft copolymerization of chitosan (Ch) with N-isopropyl acrylamide (NIPAM) and its binary comonomers acrylic acid, acrylamide and acrylonitrile in presence of azo-bis(isobutyronitrile) (AIBN) as free radical initiator and N,N′-methylene bisacrylamide (MBA) cross-linker. FTIR, XRD, SEM and TGA/DTA techniques were used to describe the structural aspects of cross-linked graft copolymers. The improvement in swelling properties of the synthesized hydrogels was utilized to explore their potential for sorption of toxic metal ions from aqueous solutions. Metal ion sorption by synthesized cross-linked adsorbents was studied as a function of the change in contact time, pH, temperature and concentration of metal ions from a solution of individual metal ions. Selective sorption of metal ions was performed by immersing polymeric samples in a solution containing four metal ions in the same concentration. Candidate polymers showed preferential sorption of metal ions in order of Cu(II)>Pb(II)>Fe(II)>Cr(VI) ions. Cross-Ch-g-poly(NIPAM-co-AAc), Cross-Ch-g-poly(NIPAM-co-AAm) and Cross-Ch-g-poly(NIPAM), showed best results for sorption of all ions from single and four component solutions.

An optimized transient technique and flow modeling for laboratory permeability measurements of unconventional gas reservoirs with tight structure

Considering the significance of pressure-dependent-permeability in characterizing fluid flow and production from gas reservoirs and the inaccuracy of the conventional transient technique in laboratory permeability measurements of core samples from unconventional reservoirs with tight structure and strong sorption potential, the conventional transient technique is optimized by using two equal-sized gas reservoirs mounted in the up and downstream sides of the experimental setup and creating same magnitude of pressure pulses in each reservoir concurrently. Applicability of the optimized transient technique is examined through both numerical simulation and laboratory tests. A mathematical model is firstly developed to numerically investigate fluid flow behavior in time and space domain. The results from numerical simulation showed that the optimized technique can greatly improve the efficiency and accuracy of the measurement, because a steady flow state as a function of time can be achieved much faster in comparison with the conventional transient technique when the same magnitude of initial pressure difference is established between the two ends of the sample. Given the difference in experimental design and procedures between the conventional and the optimized technique, it is questionable whether currently used analytical solutions developed for the conventional technique for permeability calculation can be applied for the optimized technique. Therefore, an analytical solution, corresponding to the optimized transient technique, has been then theoretically derived. It is finally experimentally verified that accurate permeability results can be obtained based on late-time pressure responses by the derived analytical solution. The optimized experimental method is capable of extending the application of the transient technique into permeability measurements of rocks with tight structure and strong gas sorption potential, providing a more reliable approach for laboratory permeability tests.

Biochar for volatile organic compound (VOC) removal: Sorption performance and governing mechanisms

Sorption is one of the most efficient and low cost strategies for volatile organic compound (VOC) removal, but VOC sorption by biochar has seen limited research. In this work, gas phase sorption experiments were conducted to determine the sorption potential and mechanisms of VOCs onto biochar. A total of 15 biochars produced from 5 common feedstocks at 300, 450, and 600°C were evaluated as sorbents. Three common VOCs (acetone, cyclohexane, and toluene) were chosen as sorbates. The results showed that all the tested biochars had VOC sorption capacity in the range of 5.58–91.2mgg−1. The sorption capacities were mainly influenced by both the surface area of biochar and its noncarbonized organic matter content. The vapor sorption process was exothermic, and the removal of VOCs by the biochars decreased with increasing feedstock temperature. Both the physical adsorption and partition mechanisms played important roles in controlling the VOC removal by the biochars. Biochar maintained its VOC removal ability after five consecutive sorption-desorption cycles, which indicated good reusability. Findings of this work suggest that biochar is a promising alternative sorbent for gaseous VOC removal.

Screening of sorbents for recovery of succinic and itaconic acid from fermentation broths

AbstractBACKGROUNDThe di‐carboxylic acids succinic acid and itaconic acid are promising building block chemicals that can be produced through fermentation, but the processes would benefit from enhancements in product recovery. While sorption has already been studied to some extent for succinate/succinic acid removal, literature on the potential of sorption for itaconic acid recovery is scarce. This work aimed to screen a range of sorbents and/or resins for their capacity to separate both acids from fermentation broths, envisaging both ex situ and in situ product recovery applications.RESULTSStatic batch screening led to a shortlist of four promising products. These were further characterized in terms of dynamic sorption capacity, regenerability, acid recovery, ability to concentrate the product and stability during sorption–desorption cycles. Final tests with real fermentation broth gave unsatisfactory results for succinic acid recovery. For itaconic acid, promising results were obtained both on synthetic solutions and on a real fermentation broth.CONCLUSIONWhile it is doubtful that adsorption will be the process of choice for in situ or ex situ succinic acid recovery, well performing sorbents could be identified for itaconic acid recovery from fermentation broths, offering perspectives for in situ product recovery applications. © 2017 Society of Chemical Industry

Investigating the Relation Between Sorption Tendency and Hydraulic Properties of Shale Formations

Routine measurement of hydraulic diffusivity of ultralow permeability rocks, such as shale, is a prolonged process. This study explores the effects of a sorptive characteristic of the porous medium on hydraulic diffusivities of shale rocks. The examined rock types include Mancos Shale, Catoosa Shale, Eagle Ford Shale, and core samples from the Gulf of Mexico. First, the adsorption isotherms of the selected shale rocks were obtained. Then, the hydraulic properties of the selected shale rocks were determined using Shale/Fluid Interaction Testing Cell, which employs pore pressure transmission technique. The experimental results show that the moisture content of shale is correlated with water activity using a multilayer adsorption theory. It is found that the adsorption isotherms of various shale formations can be scaled using their respective cation exchange capacity (CEC) into a single adsorption curve. Analyzing the transient pore pressure response in the downstream side of shale sample allows calculating the transport coefficients of shale samples. Hydraulic properties of shales are obtained by matching the pore pressure history with one-dimensional coupled fluid flow model. The experimental results indicate that sorptive properties can be inversely related to the hydraulic diffusivity of shale rocks. It is found that with an increase in the magnitude of sorption potential of shale, the hydraulic diffusivity decreases. This study is useful for shale characterization and provides a correlation, which can have various applications including, but not limited to, wellbore stability prediction during well planning.

Mechanistic understanding of crystal violet dye sorption by woody biochar: implications for wastewater treatment.

Dye-based industries, particularly small and medium scale, discharge their effluents into waterways without treatment due to cost considerations. We investigated the use of biochars produced from the woody tree Gliricidia sepium at 300°C (GBC300) and 500°C (GBC500) in the laboratory and at 700°C from a dendro bioenergy industry (GBC700), to evaluate their potential for sorption of crystal violet (CV) dye. Experiments were conducted to assess the effect of pH reaction time and CV loading on the adsorption process. The equilibrium adsorption capacity was higher with GBC700 (7.9mgg-1) than GBC500 (4.9mgg-1) and GBC300 (4.4mgg-1), at pH 8. The CV sorption process was dependent on the pH, surface area and pore volume of biochar (GBC). Both Freundlich and Hill isotherm models fitted best to the equilibrium isotherm data suggesting cooperative interactions via physisorption and chemisorption mechanisms for CV sorption. The highest Hill sorption capacity of 125.5mgg-1 was given by GBC700 at pH 8. Kinetic data followed the pseudo-second-order model, suggesting that the sorption process is more inclined toward the chemisorption mechanism. Pore diffusion, π-π electron donor-acceptor interaction and H-bonding were postulated to be involved in physisorption, whereas electrostatic interactions of protonated amine group of CV and negatively charged GBC surface led to a chemisorption type of adsorption. Overall, GBC produced as a by-product of the dendro industry could be a promising remedy for CV removal from an aqueous environment.