Microbial remediation of cadmium-contaminated soils and its mechanisms: a review / 生物工程学报

Excessive levels of cadmium (Cd) in soil exert serious negative impacts on soil ecosystems. Microorganisms are a common component of soil and show great potential for mitigating soil Cd. This review summarizes the application and remediation mechanisms of microorganisms, microbial-plants, and microbial-biochar in Cd-contaminated soil. Microorganisms such as Bacillus, Acinetobacter, Pseudomonas, and arbuscular mycorrhizal fungi (AMF) can change the biological validity of Cd through adsorption, mineralization, precipitation and dissolution. Different factors such as pH, temperature, biomass, concentration, and duration have significant effects on Cd bioavailability by microorganisms. Pseudomonas, Burkholderia, and Flavobacterium can promote the uptake of Cd2+ by hyperaccumulator through promotion and activation. Biochar, a soil amendment, possesses unique physicochemical properties and could act as a shelter for microorganisms in agriculture. The use of combined microbial-biochar can further stabilize Cd compared to using biochar alone.

Whitening toothpaste containing activated charcoal, blue covarine, hydrogen peroxide or microbeads: which one is the most effective?

Abstract The efficacy of whitening toothpastes is questionable and controversial. Clinicians, patients and researchers have expressed concern with whitening toothpastes due to the risk of wearing the dental structure and the potential for disappointment if the advertised cosmetic results are not achieved. Objective: This study compared the whitening performance of toothpastes with different whitening technologies after initial and continued use. Material and Methods: Ninety bovine incisors were stained using a concentrated solution of black tea. They were randomly distributed into 6 groups, according to the toothpaste whitening technology: activated charcoal (B&W), blue covarine (WAD), hydrogen peroxide (LWA), microbeads (Oral B 3D White Perfection - 3DW) and optimized abrasives (XW4D). They were compared to a traditional toothpaste without a whitening agent (TA - control). Specimens underwent a brushing machine with controlled pressure, time and temperature. A calibrated examiner measured the color using a VITA-Classical scale before the first brushing cycle (T0), after the first brushing cycle (TI), and after a brushing cycle that simulates continuous use (TCU). Whitening performance was evaluated by the difference of shades (ΔSGU) between T0-TI and T0-TCU timepoints, using the Kruskal-Wallis and Dunn's non-parametric test. The Wilcoxon test was used to evaluate the cumulative effect (α=0.05). Results: Statistically significant differences were observed between toothpastes in both TI and TCU (p<0.05). The time of use also had a significant effect (p<0.05). Conclusion: Only WAD and 3DW showed whitening performance after the first use (TI). The greatest whitening performance after continuous use was obtained by WAD, followed by LWA and 3DW. The use of conventional toothpaste (TA) promotes no tooth whitening. Clinical relevance: Microbead abrasives (3DW) and blue covarine (WAD) were the active technology tested that presented the best global tooth whitening performance.

[Adsorption of arsenic [III] on a natural lignocellulosic residue valued activated carbon - such cores dates]

The objective of this study, is the removal of arsenic [three] from contaminated water, by adsorption on activated carbon, prepared from a lignocellulosic natural waste in fact "the dates stones". The effectiveness of adsorption was evaluated for the carbonized raw material at 600[degree]C and after its activation at 900[degree]C. Results of the adsorption capacity tests were found to be 21mg/g for the activated carbon and barely 2mg/g before activation. The satisfactory operating conditions are carried out with pH bordering neutrality and an ambient temperature of 20[degree]C. This result is similar to that found in the litterature but for other biosorbents. The optimal adsorption of arsenic [three] follows the Langmuir and Freundlich models. The kinetics of adsorption is slow, of the second order, with a value of adsorption constant k[ads] equal to 1,16.10[-2] h[-1].

Effect of Charcoal Filter on the Emergence from Sevoflurane Anesthesia in a Semi-Closed Rebreathing Circuit

PURPOSE: A charcoal filter attached within the anesthetic circuit has been shown to efficiently adsorb halothane or isoflurane, thus hastening anesthetic recovery in low or minimal flow system. This study was intended to demonstrate whether the charcoal filter enhances the recovery time from sevoflurane anesthesia using a semi-closed circuit system. MATERIALS AND METHODS: Thirty healthy patients scheduled for elective surgery under sevoflurane anesthesia were randomly assigned to the charcoal filter or control group. Upon completion of surgery, the end-tidal concentration of sevoflurane was maintained at 2.0 vol%. A charcoal filter was attached to the expiratory limb of the breathing circuit of charcoal filter group subjects. After sevoflurane was discontinued, ventilation was controlled with the same minute volume as the intra-operative period at a fresh gas flow rate of 5 L.min(-1) with 100% O2. The elimination kinetics of sevoflurane from end-tidal concentration, Bispectral index and times of eye opening and extubation were obtained. RESULTS: The exponential time constant (tau) of alveolar sevoflurane concentration in the charcoal filter group was significantly shorter than that in the control group (1.7+/-0.5 vs. 2.5+/-1.1 min, p=0.008). The charcoal filter hastened rapid eye opening (11.1+/-3.8 vs. 14.8+/-3.0 min, p=0.007) and extubation (11.9+/-3.9 vs. 15.3+/-3.2 min, p=0.014), compared to the control group. CONCLUSION: A charcoal filter enhances the recovery from sevoflurane anesthesia with a semi-closed rebreathing circuit.

Removal of Trichloroethylene from water by adsorption on to multiwall carbon nanotubes

Groundwater recourses may be contaminated with trichloroethylene [TCE] which is used in electronic, electric, dry cleaning and other similar industries and often treated by air stripping, which TCE in its vapor form is stripped from groundwater by air and is emitted into the atmosphere without any additional treatments. Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. In this study adsorption of trichloroethylene on multiwall carbon nanotubes has been investigated. The effect of contact time, pH, initial concentration of trichloroethylene and temperature on its adsorption were investigated. Adsorption isotherms and related constants were also determined. Results showed that contact times to reach equilibrium changed from 30 min [for 150 microg/L initial concentration] to 10 min [for 600 microg/L concentrations] at 25 [degree sign]C; the equilibrium times in 40[degree sign] C were 40 min and 15 min, respectively. Multi-wall carbon nanotubes showed to act as a good adsorbent for TCE in a wide range of pH=[3-9]. For pH>9, adsorption decreased due to ionization of oxygen-containing groups. Adsorption test results revealed that TCE adsorption on the studied adsorbents could be better described by Freundlich isotherm

Efecto del carbón activado y ácido indol acético en el desarrollo de protocormos de masdevallia coccinea linden ex lindl. y maxillaria nutans lindl: in vitro / Effect of activated charcoal indol and acetic acid in the development of masdevallia coccinea linden ex lindl y maxillaria nutans lindl. protocorm like bodies under in vitro

En esta investigación se pretende estimular el desarrollo de protocormos de Masdevallia coccinea y Maxillaria nutans bajo condiciones in vitro utilizando diferentes concentraciones de ácido indol acético y carbón activado. El protocolo obtenido es una alternativa de la conservación de orquídeas que se encuentran en vías de extinción, y además permite contribuir con el mejoramiento medioambiental. En la evaluación del desarrollo vegetativo bajo condiciones in vitro de los protocormos de Masdevallia coccinea y Maxillaria nutans, orquídeas en vías de extinción, se obtuvo que solamente Maxillaria nutans alcanzará su desarrollo exitoso mediante el cultivo in vitro en el medio Murashige y Skoog (1962), donde se evaluó el efecto de la interacción entre el carbón activado (0,0; 0,5, 1,0 % (p/v)) y el ácido indol acético (0,0; 0,5; 1,0 mg/L-1). El medio de cultivo empleado fue enriquecido con sacarosa al 3% y el Myo inositol al 0,1 g/L-1. Los protocormos de Masdevallia coccinea evidenciaron que se encontraban inmaduros, situación por la cual no lograron su desarrollarlo vegetativo en el experimento planteado, en atención a que se encontraban en el periodo de latencia. Por esta razón, es de gran importancia tener en cuenta que las cápsulas de las orquídeas deben estar bien maduras, a fin de garantizar que los protocormos que se forman in vitro sean maduros y completen con facilidad su morfofisiológía. Mientras que los protocormos de Maxillaria nutans dieron un mayor rendimiento en su desarrollo vegetativo. En esta investigación se determinó que el efecto de la interacción de 0,5% de carbón activado con 0,5 mg/L-1 de AIA es positivo sobre la tasa de crecimiento para el desarrollo de los protocormos de Maxillaria nutans bajo condiciones in vitro.

The evaluation of protocorms growth of Masdevallia coccinea and Maxillaria nutans under in vitro conditions, endangered orchids, it got only Maxillaria nutans reached its successful development by culture in vitro in Murashige and Skoog (1962), which evaluated the effect of the interaction between the activated carbon (0.0, 0.5, 1,0% (w / v)) and indole acetic acid (0.0, 0.5, 1.0 mg.L-1). The culture medium used was enriched with 3% sucrose and 0.1 g/L-1 Myo inositol. Protocorms of Masdevallia coccinea, showed that they were immature, state why they did not achieve their vegetative development in the experiment raised, considering that they were in the latency period. It is therefore very important to note that the capsules of the orchid should be ripe, to ensure that protocorms formed in vitro are mature and they respond with ease morphphysiology development. While protocorms of Maxillaria nutans, gave a higher yield in its vegetative development. This research found that the interaction effect of 0.5% activated carbon with 0.5 mg/L-1 of IAA is positive on the growth rate for the development of Maxillaria nutans protocorms under in vitro conditions. The protocol obtained in this investigation is an alternative of conservation of orchids that are endangered and can contribute to further environmental improvement.

[Removal of methylene blue dye from synthetic wastewater with bone char]

Dyes are organic materials with complex structures, toxic, carcinogenic, teratogenic, nonbiodegredable properties and the most important pollutants of textile industrial wastewaters. The goal of this study was to survey the feasibility application of bone char [BC] as a sorbent for the removal of methylene blue [MB] from synthetic wastewater. The sub goals of the research were to determine the adsorption isotherm, effects of primary concentration of dye, adsorbent dose, contact time, and pH for the adsorption of MB with BC. BC was prepared under laboratory conditions by using of electrical furnace at 400°C for 2h. The prepared BC was crushed and pulverized by standard ASTM sieves with range of 10-16 mesh [1.18-2 mm]. The chemical composition and solid structure of BC was analyzed using X-ray diffraction [XRD] and scanning electronic microscopy [SEM]. Measurement of the surface area was carried out by N2 gas via BET isotherm and Belsorb software. The concentration of dye was measured by photometric method [663nm]. Predominant composition of BC is calcium hydroxyl apatite [Ca5 [PO4]3OH with 14m2/g surface area. The results of this study showed that increasing of primary concentration of dye, adsorbent dose and pH [5 to12] would lead to increasing of adsorption/removal of MB dye. Equilibration of dye adsorption was reached at lapse of 2h and optimum pH for adsorption of MB with BC found in the rage of 8.5-12. Adsorption of MB with BC complies with freundlich isotherm [R2: 0.99]. Conclusion: Bone char is a cheap component that can be used as an adsorbent in water and wastewater treatment. Based on optimum pH of 8.5-12 found for the removal of MB and the fact that many of textile industrial wastewaters have an alkaline pH, this adsorbent can be used for the removal of dyes from these wastewaters

2, 4 dichlorophenol (2, 4-DCP) sorption from aqueous solution using granular activated carbon and polymeric adsorbents and studies on effect of temperature on activated carbon adsorption.

Adsorption equilibrium, kinetics and thermodynamics of 2,4-dichlorophenol (2,4-DCP), one of the most commonly used chlorophenol, onto bituminous coal based Filtrasorb-400 grade granular activated carbon, were studied in aqueous solution in a batch system with respect to temperature. Uptake capacity of activated carbon found to increase with temperature. Langmuir isotherm models were applied to experimental equilibrium data of 2, 4-DCP adsorption and competitive studies with respect to XAD resin were carried out. Equilibrium data fitted very well to the Langmuir equilibrium model. Adsorbent monolayer capacity 'Q0, Langmuir constant 'b' and adsorption rate constant 'k(a)' were evaluated at different temperatures for activated carbon adsorption. This data was then used to calculate the energy of activation of adsorption and also the thermodynamic parameters, namely the free energy of adsorption, deltaG0, enthalpy of adsorption, deltaH0 and the entropy of adsorption deltaS0. The obtained results showed that the monolayer capacity increases with the increase in temperatures. The obtained values of thermodynamic parameters showed that adsorption of 2,4 DCP is an endothermic process. Synthetic resin was not found efficient to adsorb 2,4 DCP compared to activated carbon. The order of adsorption efficiencies of three resins used in the study found as XAD7HP > XAD4 > XAD1180.

Removal of fluoride by thermally activated carbon prepared from neem (Azadirachta indica) and kikar (Acacia arabica) leaves.

The present investigation deals with fluoride removal from aqueous solution by thermally activated neem (Azadirachta indica) leaves carbon (ANC) and thermally activated kikar (Acacia arabica) leaves carbon (AKC) adsorbents. In this study neem leaves carbon and kikar leaves carbon prepared by heating the leaves at 400 degrees C in electric furnace was found to be useful for the removal of fluoride. The adsorbents of 0.3 mm and 1.0 mm sizes of neem and kikar leaves carbon was prepared by standard sieve. Batch experiments done to see the fluoride removal properties from synthetic solution of 5 ppm to study the influence of pH, adsorbent dose and contact time on adsorption efficiency The optimum pH was found to be 6 for both adsorbents. The optimum dose was found to be 0.5g/100 ml forANC (activated neem leaves carbon) and 0.7g/100 ml forAKC (activated kikar leaves carbon). The optimum time was found to be one hour for both the adsorbent. It was also found that adsorbent size of 0.3 mm was more efficient than the 1.0 mm size. The adsorption process obeyed Freundlich adsorption isotherm. The straight line of log (qe-q) vs time at ambient temperature indicated the validity of langergren equation consequently first order nature of the process involved in the present study. Results indicate that besides intraparticle diffusion there maybe other processes controlling the rate which may be operating simultaneously. All optimized conditions were applied for removal of fluoride from four natural water samples.

Adsorption studies on wastewaters from cypermethrin manufacturing process using activated coconut shell carbon.

Cypermethrin is a pyrethroid pesticide and is used in the control of a wide range of insects on crops like vegetables, cereals, maize etc. In the present study, the adsorption efficiency of coconut shell based activated carbon for the removal of color and organic matter from cypermethrin pesticide manufacturing industrial wastewater was investigated. Effect of carbon dosage, pH and contact time on the removal of COD was also studied. Equilibrium and kinetic studies were carried out and the data was fitted in Freundlich and Langmuir models. The study proved that activated coconut shell carbon (acc) is an efficient adsorbent for treatment of cypermethrin industrial wastewaters under study.

Scavenging of Ni(II) metal ions by adsorption on PAC and babhul bark.

The removal of toxic nickel metal ions by adsorption, using powder activated charcoal (PAC) and non-conventional adsorbent modified Indian powder babhul bark (PBB), was studied at room temperature. The adsorption isotherms were obtained in a batch reactor. It is observed that, the process of uptake followed first-order adsorption rate expression and obeyed Langmuir and Freundlich models of adsorption. Effects of variations in parameters such as pH, contact time, adsorbent dose, initial Ni(II) concentration and particle size were also studied.

Studies on fluoride removal using adsorption process.

Batch adsorption studies were undertaken to assess the suitability of commercially available activated charcoal to remediate fluoride-contaminated water. The effects of some of the major parameters of adsorption, viz. pH, dose of adsorbent, rate of stirring, contact time and initial adsorbate concentration on fluoride removal efficiency were studied and optimized. The optimum sorbent dose was found to be 2.0 g/100 mL, equilibrium was achieved in 120 minutes and enhanced adsorption was obtained at pH 2. Maximum fluoride removal was observed to be 94% at optimum conditions. Freudlich as well as Langmuir isotherms were plotted and kinetic constants were determined.

Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal

This research focuses on understanding biosorption process and developing a cost effective technology for treatment of heavy metals-contaminated industrial wastewater. A new composite biosorbent has been prepared by coating chitosan onto acid treated oil palm shell charcoal (AOPSC). Chitosan loading on the AOPSC support is about 21 percent by weight. The shape of the adsorbent is nearly spherical with particle diameter ranging 100~150 µm. The adsorption capacity of the composite biosorbent was evaluated by measuring the extent of adsorption of chromium metal ions from water under equilibrium conditions at 25ºC. Using Langmuir isotherm model, the equilibrium data yielded the following ultimate capacity values for the coated biosorbent on a per gram basis of chitosan: 154 mg Cr/g. Bioconversion of Cr (VI) to Cr (III) by chitosan was also observed and had been shown previously in other studies using plant tissues and mineral surfaces. After the biosorbent was saturated with the metal ions, the adsorbent was regenerated with 0.1 M sodium hydroxide. Maximum desorption of the metal takes place within 5 bed volumes while complete desorption occurs within 10 bed volumes. Details of preparation of the biosorbent, characterization, and adsorption studies are presented. Dominant sorption mechanisms are ionic interactions and complexation.

Adsorptive removal of basic dyes from aqueous phase onto activated carbon of used tea leaves: a kinetic and thermodynamic study.

Activated carbon has been prepared from used tea leaves impregnated with H3PO4 (50%, w/v) and carbonized at 300 degrees C. Its adsorption capacity has been tested for the decolourisation of wastewater containing malachite green and methylene blue. The effect of system variables such as concentration, temperature, pH, contact time, adsorbent dosage and particle size was studied. The optimum pH range is 8-10 and dosage required is 1.2 g/L for 100% removal of both malachite green and methylene blue (100 mg/L). Break-through and exchaustive capacities for malachite green and methylene blue are 300.0 and 314.7 mg/g; 275.0 and 290.4 mg/g, respectively. The adsorption data follow Langmuir model as well as Freundlich model.