Potential Remediation Method Research Articles

Removal of tetracycline in the water by a kind of S/N co-doped tea residue biochar

Tetracycline (TC) is widely present in the environment, and adsorption technology is a potential remediation method. S/N co-doped tea residue biochar (SNBC) was successfully prepared by hydrothermal carbonization method using tea residue as raw material. S was doped by Na2S2O3·5H2O, and N was doped by N in tea residue. The adsorption efficiency of SNBC could reach 94.16% when the concentration of TC was 100 mg L−1. The adsorption effect of SNBC on TC was 9.38 times more than that of unmodified biochar. Tea biochar had good adsorption effect at pH 4–9. The maximum adsorption capacity of 271 mg g−1 was calculated by the Langmuir isotherm model. The adsorption mechanism involved many mechanisms such as pore filling, π-π interaction and hydrogen bonding. The adsorbent prepared in this study could be used as an effective adsorbent in the treatment of TC wastewater.

Investigation of airborne nanoparticles emitted during the laser cleaning process of corroded metal surface

Laser surface cleaning is a promising surface-cleaning technique owing to its numerous benefits, including its noncontact behavior, ease of control, high precision, and no secondary waste generation. However, it cannot prevent airborne nanoparticle emissions during the laser cleaning process. Therefore, the effects of laser-cleaning parameters on airborne nanoparticle generation are analyzed to design potential remediation methods. In this study, the nanoparticles released during the laser cleaning of corroded 304L stainless steel surfaces were investigated. Electrical low-pressure impactor analysis and electron microscopy were conducted to determine how laser parameters influenced the size and amount of emitted nanoparticles. Based on these findings, the feasibility of the filtering emitted nanoparticles using high-efficiency particulate air filters was examined.

Exploring the Potential of Utilizing Aquatic Macrophytes for Enhanced Phytoremediation of Zinc in Artificial Wastewater: Characteristics and Parameter Studies

Heavy metal pollution due to industrialization can threaten the surrounding environment and living organisms. Phytoremediation is a green technique that uses hyperaccumulator plants to eliminate or decrease heavy metals in polluted water bodies. The aim of this study was to investigate the changes in morphology of Pistia stratiotes (water lettuce) and Eichhornia crassipes (water hyacinth) before and after phytoremediation of zinc (Zn) by using scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The SEM images showed the formation of small granular aggregates on the surfaces of the leaf and root. EDX results confirmed the uptake of Zn metal, especially in the plant roots. The FTIR spectra showed the Zn metal binding with several characteristic functional groups (O-H, C-H and C=O bonds). Different parameters were also studied to optimize the Zn uptake rate. Water lettuce achieved 80.1% phytoremediation of Zn after 5 days at optimum conditions (10 ppm of Zn, 6 ppm of sodium chloride and natural solution pH). Meanwhile, water hyacinth reached up to 88% when increasing the sodium chloride up to 9 ppm. In conclusion, Zn phytoremediation using both plants can be a potential remediation method for improving the quality of water.

A Review on Pollutants Found in Drinking Water in Sub-Sahara African Rural Communities: Detection and Potential Low-cost Remediation Methods

Water is the most essential substance that supports various life mechanisms. It is a fundamental and necessary requirement for mankind and all other living creatures on the planet. Therefore, daily drinking water should be clean, readily available, sufficient, and free from harmful substances. However, in many rural areas, most sources of drinking water are assumed to be safe for human consumption, but this is not always the case. This work aims to provide a review of pollutants found in the drinking water of Sub-Saharan rural communities and explore potential low-cost remediation methods. The assessment of water pollutants and their remediation methods has been the primary focus of research for several years. Additionally, the World Health Organisation has established various minimum standards regarding the concentration of common pollutants in water. This review presents the major sources of water, the origin of contaminants, the different types of pollutants, and remediation methods to enhance the current knowledge in the field of rural drinking water contaminants.

Biochar supported nanoscale zero-valent iron for the kinetics removal and mechanism of decabromodiphenyl ethane in the sediment.

The extensive applications of decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, have induced its accumulation in sediment, which may have a great negative impact on the ecological environment. In this work, the biochar/nano-zero-valent iron materials (BC/nZVI) were synthesized to remove DBDPE in the sediment. Batch experiments were carried out to investigate the influencing factors of the removal efficiency, and kinetic model simulation and thermodynamic parameter calculation were performed. The degradation products and mechanisms were probed. The results indicated that the addition of 0.10g·g-1 BC/nZVI to the sediment with an initial concentration of 10mg·kg-1 DBDPE could remove 43.73% of DBDPE during 24h. The water content of the sediment was a critical factor in the removal of DBDPE, which was optimal at 1:2 of sediment to water. The removal efficiency and reaction rate were enhanced by increasing dosage, water content, and reaction temperature or decreasing initial concentration of DBDPE based on the fitting results of the quasi-first-order kinetic model. Additionally, the calculated thermodynamic parameters suggested that the removal process was a spontaneously and reversibly endothermic reaction. The degradation products were further determined by GC-MS, and the mechanisms were presumed that DBDPE was debrominated to produce octabromodiphenyl ethane (octa-BDPE). This study provides a potential remediation method for highly DBDPE-contaminated sediment by using BC/nZVI.

Mixed bacteria passivation for the remediation of arsenic, lead, and cadmium: Medium optimization and mechanisms

Lead(Pb), cadmium(Cd), and arsenic(As) are highly bioaccumulative and hazardous to human health. In this study, the effectiveness and mechanism of mixed bacteria applied to Pb, Cd, and As complex contaminated soil were investigated. According to the one factor per time (OFT) method, the optimal medium consisted of 10 g/L corn pulp dry powder, 10 g/L glucose, 3.8 g/L dipotassium hydrogen phosphate, 0.5 g/L sulfate, 1 g/L trisodium citrate at pH 7.2. The gradient test showed that the key fermentation process conditions were the optimal inoculum level of 1% and incubation temperature of 37 ℃. Then the mixed bacteria agent was used to treat the Pb(II), Cd(II), and As(III) contaminated soil. The adsorption amounts of Pb(II), Cd(II), and As(III) by the mixed bacteria were 10.39 μg/g, 1.65 μg/g, and 67.03 μg/g, respectively. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy(XPS) analyses showed that the remediation mechanism of three metals by mixed bacteria involved in extracellular polymer adsorption, biomineralization, and oxidation. This study would provide a potential remediation method for the multi-heavy metal polluted soil.

Constructing Ni4/Fe@Fe3O4-g-C3N4 nanocomposites for highly efficient degradation of carbon tetrachloride from aqueous solution

Catalytic hydrodechlorination is one of the most potential remediation methods for chlorinated organic pollutants. In this study, Ni4/Fe@Fe3O4-g-C3N4 (NFFOCN) nanocomposites were synthesized for carbon tetrachloride (CT) removal and characterized by SEM, XPS and FTIR. The characterization results demonstrated that the special functional groups of g-C3N4, especially NH groups, effectively alleviated the aggregation of nanoparticles. In addition, the C and N groups of g-C3N4 enhanced the catalytic dechlorination of CT by providing binding sites. The experimental results showed that NFFOCN could effectively remove CT over a wide initial pH range of 3–9, and the CT removal efficiency reached 94.7% after 35 min with only 0.15 g/L of NFFOCN at pH 5.5. The Cl−, SO42−, and HCO3− promoted the removal of CT, while HA and NO3− had the opposite effect. Furthermore, good sequential CT removal by NFFOCN nanocomposites was observed, and the CT removal efficiency reached 77.3% after four cycles. Based on the identification of products, a possible degradation pathway of CT was proposed. Moreover, the main mechanisms regarding CT removal included the direct reduction of nZVI (about 40.51%), adsorption (around 34.79%), and hydrodechlorination of CT by Ni0 using H2 (about 19.40%).

Bioremediation of petroleum-contaminated saline soil by Acinetobacter baumannii and Talaromyces sp. and functional potential analysis using metagenomic sequencing

Microbial remediation is a potential remediation method for petroleum-contaminated soil. In order to explore the petroleum degradation mechanism by microorganisms, the oilfield soil was remedied by Acinetobacter baumannii combined with Talaromyces sp. The degradation mechanism was studied by analyzing soil microbial community and functional genes through metagenomics during the degradation process. The result showed the degradation rate of petroleum was 65.6% after 28 days. The concentration of petroleum decreased from 1220 mg/kg to 420 mg/kg. In the co-culture group, Acinetobacter baumannii became the dominant species, the annotated genes of it at the species level accounted for 7.34% while that of Talaromyces sp. accounted for only 0.34%. Meanwhile, the annotated genes of Bacillus, Halomonas, and Nitriliruptor at the genus level were up-regulated by 1.83%, 0.90%, and 0.71%, respectively. In addition, large functional genes were significantly up-regulated, including the peroxisome, P450 enzyme (CYP53, CYP116, CYP102, CYP645), and biofilm formulation, promoting the oxidation and hydroxylation, and catalyzing the epoxidation of aromatic and aliphatic hydrocarbons. Meanwhile, the degrading genes of alkanes and aromatic hydrocarbons were expressed promotionally, and degradation pathways were deduced. In conclusion, the inoculation of Acinetobacter baumannii combined with Talaromyces sp. accelerated the degradation of petroleum in oilfield soil and improved the growth of indigenous petroleum-degrading bacteria. Many functional genes related to petroleum degradation were promoted significantly. These results proved the co-culture of bacteria-fungi consortium contributes to the bioremediation of petroleum-contaminated soil.

Contrasted effects of Metaphire guillelmi on tetracycline diffusion and dissipation in soil

Earthworms are important in soil bioremediation because of their capability of pollutant degradation. However, the trade-off between pollutant dissemination and degradation arising from earthworm activities remains unclear, as well as the potential biodegradation mechanism. Herein, an earthworm avoidance experiment was established to investigate Metaphire guillelmi–mediated tetracycline (TC) diffusion and degradation. The results showed that above 1600 mg kg−1 TC pollution in soil induced avoidance behaviour of earthworms (p < 0.05), below which the random worm behaviour accelerated TC diffusion by 8.2% at most (p < 0.05), resulting in elevated levels of antibiotic-resistant bacteria and genes in the soil. Nevertheless, earthworms enhanced TC degradation regardless of whether their avoidance behaviour occurred (14.6–25.8%, p < 0.05). Compared with in soil, metabolic pathways affiliated with xenobiotic degradation and metabolism in the intestines were enriched (LDA >3). Given the abundant glutathione S-transferases in the intestines and their close relationship with Δ degradation, they may play a key role in intestinal TC biodegradation. In general, earthworms had good tolerance to soil TC contamination and their impact on promoting TC degradation outweighed that accelerating TC diffusion. This work provides a comprehensive view of earthworms as a potential remediation method for TC-contaminated soil.

Phytoremediation of palm oil mill effluent (POME) using water spinach (Ipomoea aquatica Forsk)

Rapid expansion of palm oil industry poses potential threat to terrestrial environment and aquatic ecosystems as it discharges high volume and various forms of solid and liquid waste substances as by-products, known as palm oil mill effluent (POME) during oil processing. Indiscremental disposal of POME is a major source of wastewater contamination which could have catastrophic impact on the environment. Thus, remediation of POME is crucial before it released to the environment. Phytoremediation using aquatic plants including water spinach (Ipomoea aquatica) has potential to improve the quality of POME. This present study investigated the phytoremediation efficiency of POME, which contains high amount of chemical oxygen demand (COD), nitrate, phosphate using water spinach for up to 15 days and described its impact on the growth performance. Experimental design of this study consisted of five treatments with three replications namely: control: 0% POME (0 L POME + 10 L tap water), Treatment A: 25% POME (2.5 L POME + 7.5 L tap water), Treatment B: 50% POME (5 L POME+ 5 L tap water), Treatment C: 75% POME (7.5 L POME + 2.5 L tap water), and Treatment D: 100% POME (10 L POME). The results indicated that water spinach was able to reduce COD, nitrate, phosphate and color as 86.3%, 21.5%, 90.9 % and 95.3%, respectively. Water spinach had no influence on the growth performance even up to 75% of POME containing media. Furthermore, results showed that high concentrations of POME damage root structures, and ultimately impact the growth performance of water spinach. In conclusion, phytoremediation using water spinach can be a potential remediation method to improve the quality of COD, phosphate and nitrate.

Hydroxyapatite as a passivator for safe wheat production and its impacts on soil microbial communities in a Cd-contaminated alkaline soil

The remediation of Cd-contaminated alkaline soil plays a critical role in safe wheat production. In this study, hydroxyapatite (HAP), a functional environmental remediation material, was selected to investigate the effects of HAP on cadmium accumulation in winter wheat (Triticum aestivum L.), Cd bioavailability in alkaline soil moderately polluted with Cd (2.46 mg kg-1) and the soil bacterial community via pot experiments. The results showed HAP effectively inhibited Cd accumulation in the grains of two investigated wheat cultivars by hindering root uptake. The Cd concentrations decreased by 49.9–81.9%, and 35.7–92.4% in the grains of Zhoumai-30 and Zhengmai-7698, respectively. HAP increased the soil pH and reduced the bioavailability of Cd. 16S rRNA sequencing analysis indicated that the changes of soil physicochemical properties changed the diversity and composition of the bacterial community by increasing the relative abundance of beneficial soil bacteria. These results demonstrated the application of 2.5% HAP combined with planting Zhengmai-7698 treatment was a potential remediation method for safe wheat production, and also benefited soil P and N cycling by increasing the relative abundance of beneficial bacteria. The good performance of HAP in inhabiting Cd accumulation in wheat grains indicated it is a promising material for safe wheat production.

Processing Aids in Food and Beverage Manufacturing: Potential Source of Elemental and Trace Metal Contaminants.

There are currently increased efforts to determine potential sources of trace metal contaminants in the food supply. While there are likely many sources of these elements, processing of foods has gained attention as one such route. Research is reviewed on how processing aids used for food production, including beverage filtration and fining, have been targeted as potential sources of trace metals. Potential remediation methods to reduce elemental transfer occurring during processing is discussed. While food processing aids are often a critical part of food manufacturing, they can be a potential source of trace metal contaminants, including heavy metals.

Goethite-modified biochar restricts the mobility and transfer of cadmium in soil-rice system.

Cadmium (Cd) contamination of paddy soils has raised serious concerns for food safety and security. Remediation and management of Cd contaminated soil with biochar (BC) and modified biochar is a cost-effective method and has gained due attention in recent years. Goethite-modified biochar (GB) can combine the beneficial effects of BC and iron (Fe) for remediation of Cd contaminated soil. We probed the impact of different BC and GB amendments on Cd mobility and transfer in the soil-rice system. Both BC and GB effectively reduced Cd mobility and availability in the rhizosphere and improved the key growth attributes of rice. Although BC supply to rice plants enhanced their performance in contaminated soil but application of 1.5% GB to the soil resulted in prominent improvements in physiological and biochemical attributes of rice plants grown in Cd contaminated soil. Sequential extraction results depicted that BC and GB differentially enhanced the conversion of exchangeable Cd fractions to non-exchangeable Cd fractions thus restricted the Cd mobility and transfer in soil. Furthermore, supplementing the soil with 1.5% GB incremented the formation of iron plaque (Fe plaque) and boosted the Cd sequestration by Fe plaque. Increase in shoot and root biomass of rice plants after GB treatments positively correlates with incremented chlorophyll contents and gas exchange attributes. Additionally, the oxidative stress damage in rice plants was comparatively reduced under GB application. These findings demonstrate that amending the soil with 1.5% GB can be a potential remediation method to minimize Cd accumulation in paddy rice and thereby can protect human beings from Cd exposure.

Tracing and quantifying contributions of end members to karst water at a coalfield in southwest China

Karst water, which provides 25% of the world's drinking water, is especially vulnerable to anthropogenic contamination. Such is the case in southwestern China with trace element pollution in important karst aquifers. Approximately 20% of the total study area consisted of abandoned mine tailings with elevated concentrations of Fe, S, Mn, As, Cu, and Cr. Acid mine drainage (AMD) water originating from pyrite oxidation of the tailings was characterized by low pH and high concentrations of Fe, SO42−, and As. Concentrations of Fe, Mn, Al, SO42−, As, Cd, and Pb in spring water in wet and dry seasons were greater than WHO and USEPA drinking water guidelines. Based on the results of mineral characterizations, hydrogeochemistry, and isotopic compositions (δ34SSO4, δ18OSO4, and δ18OH2O), the chemistry of AMD water was primarily controlled by pyrite oxidation, river water by atmospheric precipitation, and spring water by carbonate rock dissolution and mixing with river and AMD waters. A three-end-member mixing model identified the contributions of these different end members to spring water quality. Although AMD water was characterized by the lowest mixing percentages during the wet (14.1%) and dry (26.9%) seasons, it played a very important role in degrading spring water quality. Based on these findings, an investigation strategy was developed for illuminating seasonal water quality and potential remediation methods corresponding to the contaminants in the spring water are also proposed to manage this seriously polluted karst system. Results could benefit remediation planning for these distinctively complex and vulnerable systems in other regions of the world.

Removal of heavy metals Pb(II), Cd(II) and Cu(II) from waste waters using synthesized chromium doped nickel oxide nano particles

Adsorption of metal ions Pb(II), Cd(II) and Cu(II) are observed on chromium doped nickel nano metal oxide. Chromium doped nickel oxide was synthesized by combustion technique using glycine as a fuel. In this work, transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) are applied to study the composition and structure of chromium doped nickel oxide. Batch equilibrium experiments were performed to study the removal efficiency of heavy metal ions. The effects of different parameters such as contact time, pH and adsorbent dose on the adsorption process were investigated. The adsorption kinetics and adsorption isotherms studies were also performed. The formation of hydroxide on the surface of chromium doped nickel oxide could be the main factor of cations removal due to its high adsorption affinity for aqueous solutes. Chromium doped nickel oxide may offer a potential remediation method for the removal of metals from water and environment. KEY WORDS : Adsorption isotherms, BET, Adsorption efficiency, Batch equilibrium, Adsorption kinetics Bull. Chem. Soc. Ethiop. 2018 , 32(2), 225-238. DOI: https://dx.doi.org/10.4314/bcse.v32i2.4

Removal of Pb, Cd, Cu and Ni from aqueous solution using nano scale zero valent iron particles

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions Pb(II), Cd(II), Cu(II), Ni(II) to nano zero valent iron (nZVI) particles of surface iron oxide was examined. nZVI particles were synthesized by reduction of ferric chloride with sodium borohydride. In this work, transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy are applied to study the compositional and structural of nZVI. Batch equilibrium experiments were performed to study the removal efficiency of heavy metal ions. The effect of different parameters such as contact time, initial concentration, pH and nZVI dose on the adsorption process were investigated. The adsorption kinetics well fitted using a pseudo-second order kinetic model. SEM and TEM images showed that of particles were mostly spherical shape in chains with an average size 43.1±11.9nm. The initial sorption rate for all the metals is in order Pb2+>Cu2+>Cd2+>Ni2+. Short adsorption equilibrium contact time favors the application of the adsorption process. The formation of FeOOH on the surface of nZVI could be the main factor of cations removal due to its high adsorption affinity for aqueous solutes. Therefore, with the strong adsorption at pH<6.5 which is representative of several natural groundwater and the ability to adsorb multiple metal ions simultaneously, nZVI may offer a potential remediation method for the removal of metals from water and environment.

Application of Rice-Straw Biochar and Microorganisms in Nonylphenol Remediation: Adsorption-Biodegradation Coupling Relationship and Mechanism.

Biochar adsorption presents a potential remediation method for the control of hydrophobic organic compounds (HOCs) pollution in the environment. It has been found that HOCs bound on biochar become less bioavailable, so speculations have been proposed that HOCs will persist for longer half-life periods in biochar-amended soil/sediment. To investigate how biochar application affects coupled adsorption-biodegradation, nonylphenol was selected as the target contaminant, and biochar derived from rice straw was applied as the adsorbent. The results showed that there was an optimal dosage of biochar in the presence of both adsorption and biodegradation for a given nonylphenol concentration, thus allowing the transformation of nonylphenol to be optimized. Approximately 47.6% of the nonylphenol was biodegraded in two days when 0.005 g biochar was added to 50 mg/L of nonylphenol, which was 125% higher than the relative quantity biodegraded without biochar, though the resistant desorption component of nonylphenol reached 87.1%. All adsorptive forms of nonylphenol (f rap, f slow, f r) decreased gradually during the biodegradation experiment, and the resistant desorption fraction of nonylphenol (f r) on biochar could also be biodegraded. It was concluded that an appropriate amount of biochar could stimulate biodegradation, not only illustrating that the dosage of biochar had an enormous influence on the half-life periods of HOCs but also alleviating concerns that enhanced HOCs binding by biochar may cause secondary pollution in biochar-modified environment.

Using pre-screening methods for an effective and reliable site characterization at megasites

This paper illustrates the usefulness of pre-screening methods for an effective characterization of polluted sites. We applied a sequence of site characterization methods to a former Soviet military airbase with likely fuel and benzene, toluene, ethylbenzene, and xylene (BTEX) contamination in shallow groundwater and subsoil. The methods were (i) phytoscreening with tree cores; (ii) soil gas measurements for CH4, O2, and photoionization detector (PID); (iii) direct-push with membrane interface probe (MIP) and laser-induced fluorescence (LIF) sensors; (iv) direct-push sampling; and (v) sampling from soil and from groundwater monitoring wells. Phytoscreening and soil gas measurements are rapid and inexpensive pre-screening methods. Both indicated subsurface pollution and hot spots successfully. The direct-push sensors yielded 3D information about the extension and the volume of the subsurface plume. This study also expanded the applicability of tree coring to BTEX compounds and tested the use of high-resolution direct-push sensors for light hydrocarbons. Comparison of screening results to results from conventional soil and groundwater sampling yielded in most cases high rank correlation and confirmed the findings. The large-scale application of non- or low-invasive pre-screening can be of help in directing and focusing the subsequent, more expensive investigation methods. The rapid pre-screening methods also yielded useful information about potential remediation methods. Overall, we see several benefits of a stepwise screening and site characterization scheme, which we propose in conclusion.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-015-4649-6) contains supplementary material, which is available to authorized users.

Review of Chromite Ore Processing Residue (COPR): Past Practices, Environmental Impact and Potential Remediation Methods

Chromite ore processing residue (COPR) is a waste byproduct of chromate production that contains high levels of hexavalent chromium (Cr(VI)). Although the high temperature chromite process was banned in several countries, its legacy still exists at numerous contaminated sites. For instance, New Jersey alone has over 2 million tons of waste COPR. Legacy sites are confounded by the fact that a few countries still produce COPR during chromate extraction that leads to new contamination. This paper reviews the historical production and disposal practices of COPR and provides a concise overview of the different methods for addressing Cr(VI) contamination at old and new COPR sites.

Effects of Experimental Thermocline and Oxycline Deepening on Methylmercury Bioaccumulation in a Canadian Shield Lake

Environmental disturbances like deforestation or climate change may influence lake thermal and oxic stratification, thereby modifying cycles of contaminants such as mercury (Hg). In a lake naturally separated into three basins, the thermocline and oxycline of an experimental basin were deepened by 4 and 3 m, respectively, to study the effect on the methylmercury (MeHg) accumulation. This treatment decreased hypolimnetic MeHg concentration by approximately 90%, zooplankton concentrations by 30 to 50%, and in some fish by 45%. A multiple linear regression indicated that oxycline depth significantly influenced hypolimnetic MeHg concentrations, with no significant effect of thermocline depth, anoxic water volume, interface area of oxic-anoxic water, and sediment area in contact with anoxic water. Fish MeHg decline varied, with a greater response by low oxygen-tolerant bullhead. Increased pelagic primary and secondary production likely caused zooplankton and fish MeHg decreases via algal and growth dilution. Environmental changes leading to oxycline deepening are therefore predicted to cause a decrease in MeHg bioaccumulation in similar Canadian Shield lakes. If associated ecosystem impacts related to the deepening treatment are deemed acceptable, then this experiment provides a potential remediation method for small lakes confronted with MeHg accumulation.