Environmental Technology

Yamada, Kazunori; Kitao, Yoshinori; Asamoto, Hiromichi; Minamisawa, Hiroaki

doi: 10.1080/09593330.2021.2020339pmid: 34919032

A polymeric adsorbent for removal of hexavalent chromium (Cr(VI)) ions was developed by the photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to a polyethylene (PE) mesh and subsequent quaternization with iodoalkanes of different alkyl chain lengths. The grafting of DMAEMA and subsequent quaternization were verified by the FT-IR and XPS measurements. The Cr(VI) ion adsorption capacity of the DMAEMA-grafted PE meshes had the maximum value at the grafted amount of 2.6 mmol/g in a 0.20 mM K2Cr2O7 solution at pH 3.0 and 30°C. The adsorption behaviour obeyed the pseudo-second order kinetic model and well expressed by Langmuir isotherm. These results suggest that the Cr(VI) ion adsorption occurs through the electrostatic interaction mainly between protonated dimethylamino groups and hydrochromate (HCrO4 -) ions. The adsorption capacity of the quaternized PE-g-PDMAEMA meshes increased with an increase in the degree of quaternization and/or the alkyl chain length of the iodoalkanes used and the maximum adsorption ratio was obtained at the degree of quaternization of 54.2% for the iodoheptane-quaternized PE-g-PDMAEMA (PE-g-QC7PDMAEMA) mesh. This value was about 1.86 times higher than that of the PE-g-PDAMEMA mesh. Cr(VI) ions were successfully desorbed from the PE-g-PDMAEMA and PE-g-QC7PDMAEMA meshes in eluents such as NaOH, NaCl, and NH4Cl. In 0.50 M NaCl, 0.10 M NH4Cl, and 0.50 mM NaOH, the adsorption and desorption process was repeatedly performed without any considerable decrease and the desorption behaviour obeyed the pseudo-second order kinetic model. These results emphasise that the PE-g-PDMAEMA meshes and their quaternized products can be applied as an adsorbent for Cr(VI) ions.

Liang-Tong, Zhan; Li, Zhao; Yuqing, You; Na, Hao; Bate, Bate

doi: 10.1080/09593330.2021.2020340pmid: 34919016

Iron (Fe) and manganese (Mn) are the most frequently detected heavy metals in the soil and groundwater near municipal landfill sites. Natural calcium-carbonate-based materials, such as dolomite, effectively remove metal ions and are suitable as reactive materials for permeable reactive barriers (PRBs). However, multiple heavy metals usually coexist in contaminated groundwater, the effectiveness and competitive precipitation mechanisms in the removal of Fe(III) and Mn(II) are unclear. In this study, we investigated the efficiency and influencing factors of the removal of single and coexisting Fe(III) and Mn(II) by dolomite through experimental batch and column tests, property characterization, and PHREEQC simulations. Dolomite with 1.18–2.36 mm particle size showed the best removal efficiency for Fe(III) and Mn(II) through precipitation. Fe(III) was preferentially precipitated by dolomite with higher removal efficiency, attributed to the lower solubility product (Ksp) of iron precipitates. Compared with Fe(III), Mn(II) was precipitated conditionally, and the removal efficiency was restricted by the concentration of Fe(III) in the system. Considering the application of PRB in the field, dolomite would be effective for the remediation of coexisting heavy metals with lower precipitate Ksp. The half-time of Mn(II) removal could serve as a reference for PRB thickness designs if the target metal contaminants were in a similar concentration range as Fe(III) and Mn(II). Additionally, the PRB performance could be affected by the reduction of hydraulic permeability induced by precipitation, and the fine precipitates migrating from PRB might affect downstream groundwater quality.

Mori, Takamasa; Murakami, Kotaro; Yabe, Mitsuyasu

doi: 10.1080/09593330.2021.2020908pmid: 34927556

For establishing a sustainable society, it is crucial to reuse the organic waste as a material resource. Therefore, herein, we aim to pulverize the methane fermentation residue sludge by ball milling and high-speed agitation to directly utilize it as a liquid fertilizer. The solid particles in the sludge can be below 100 µm, corresponding to the nozzle diameter of the boom sprayer by both ball milling and high-speed agitation; when ball milling was carried out for at least 1 h, the ratio of coarse particles larger than 100 µm decreased by less than 10%. In addition, the phosphate-ion concentration in the sludge increased with a decrease in the particle size of solid in the sludge mainly due to increase in its specific surface area. Furthermore, we investigated the effects of various experimental conditions for ball milling on the pulverization efficiency. Results suggests that for grinding the soft solid particles in the sludge by ball milling, the volume ratio of the total medium balls and sludge, total volumes of the balls and sludge, and inner pot volume should be larger, while the ratio of the rotation speed to the critical rotation speed should be almost the same as those reported previously in the reports on grinding of inorganic particles to attain an effective pulverization.

Whalen, Daniel A.; Duranceau, Steven J.

doi: 10.1080/09593330.2021.2021297pmid: 34927552

Seawater was investigated as an alternative regenerant source to conventional salt-imported brine solutions in an anion exchange process treating surficial Florida coastal groundwater for the removal of sulfate and organics. Bench-scale column testing revealed that filtered Sarasota Bay seawater efficiently regenerated the anion resin media; however, sulfate exchange capacity decreased by 8.42% compared with conventional 10% salt regeneration methods. Addition of 3% sodium chloride increased regeneration efficiency, reduced exchange capacity losses to 2.4% as compared to conventional 10% salt regeneration methods. Regeneration resulted in 2.13 mg/L of bromide leakage; however, addition of 3% sodium chloride to seawater reduced bromide leakage to 1.25 mg/L. A correlation between bromide exchange and the regenerant chloride-to-bromide molar ratio (CBMR) was observed, yielding less bromide exchange at higher CBMRs. Bromide adsorption followed pseudo 2nd order kinetics and chemisorption was the rate controlling step. Increasing the CBMR of the regenerant was found to shift adsorption behaviour, allowing intra-particle diffusion to occur sooner. Bromide equilibrium appeared to follow a logarithmic decay as the CBMR of the regenerant increased. Intra-particle and film diffusion mechanisms were evaluated that indicated the presence of diffusion-based processes and more than one rate controlling step. An empirical function was derived to approximate bromide equilibrium adsorption in relation to a regenerant’s CBMR. Seawater as a regenerant when enhanced with sodium chloride shows promise as an anion exchange regenerant; additionally, classification of a seawater regenerant’s CBMR can provide insight into the kinetic and equilibrium relationships of bromide exchange.

Muller, Ricardo; Vilas Boas, Marcio A.; Costa, Mônica S. S. M.; Remor, Marcelo; Alvez, Helton J.

doi: 10.1080/09593330.2021.2021453pmid: 34937526

Dairy cattle manure with bedding (CB), including manure, urine, water, and shavings, is lignocellulosic biomass and needs to be pre-treated in anaerobic reactors to enhance biomass digestibility. This study analyzed the technical and economic feasibility of physical treatment (milling) and alkaline treatment of CB for biogas production. Pre-treatment included drying, milling, and alkaline hydrolysis at room temperature for 24 h. Maximum biogas production was determined using the biochemical methane potential (BMP) test. Physicochemical analyses were performed to characterise CB before and after pre-treatment and the BMP test. The characteristics of the lignocellulosic material were examined by scanning electron microscopy. The economic feasibility (return on investment) of each treatment (USD per ton of CB) was determined. Treatment with 3% NaOH achieved the highest biogas production (771 mL per kg of volatile solids) and was 104.5% higher than that of milling and 124.7% higher than that of chemical pre-treatment with 4% NaOH. The analysis of economic feasibility showed that the payback period of treatment with 3% NaOH was 1.4 years for scenario 1 (continuous stirred tank reactor - CSTR) and 3 years for scenario 2 (covered lagoon digester). These results demonstrate the feasibility of producing biogas as a renewable energy source via the anaerobic digestion of CB.

Saoudi, Mohamed Amine; Dabert, Patrick; Ponthieux, Arnaud; Vedrenne, Fabien; Daumer, Marie-Line

doi: 10.1080/09593330.2021.2023222pmid: 35019813

Phosphorus recovery from sewage sludge as secondary raw materials or as a direct P-rich fertiliser is one of the top frontrunner solutions to tackle Phosphorus (P) scarcity and depletion. However, the efficiency of this P recovery process greatly depends on its phosphorus dissolution potential, which in return relies on the phosphorus speciation in the sewage sludge. This article investigates the potential correlation between P speciation in sewage sludge and the iron-based P removal technologies used in sewage treatment plants (STP) through an innovative sequential extraction method based on the SEDEX method that distinguishes quantitatively between ferrous bound phosphate and ferric bound phosphate. XRD and SEM-EDX were also used to characterise P and Fe species in the studied sludge qualitatively. Principal component analysis showed that the sludge characterised by P bound to ferric iron (as the dominant P fraction) are mostly correlated with sludge produced from the CPR process (chemical phosphorus removal) and primary sludge. Moreover, sludge with a non-negligible amount of P bound to ferrous iron were correlated with sludge from the mixed EBPR-CPR process (Enhanced Biological P Removal assisted with CPR). However, Vivianite was only found in CPR sludge with Fe/P molar ratio higher than 0.6.

Yao, Zhenzhen; He, Xiaoman; Yin, Mengqiuzi; Han, Han; Zhang, Qiwu

doi: 10.1080/09593330.2021.2024271pmid: 34962220

A mechanochemical (MC) method was employed for the remediation of soil contaminated with fluoranthene (C16H10, FL) a four-ringed polycyclic aromatic hydrocarbon (PAH) containing three benzene rings and a central five-membered heterocyclic ring, with the effects of soil inorganic components, milling conditions, and the degradation mechanism investigated. Results showed that the addition of SiO2 and kaolin to soil resulted in a greater increase in the effectiveness of FL removal than other inorganic additives. After 3 hours of milling at 500 rpm, the FL removal rate from SiO2 containing soil, reached 99.26%, with the removal efficiency increasing in accordance with an increase in milling duration and speed. The milled samples were characterized by FT-IR, Raman spectroscopy, and GC-MS analysis, revealing the mechanism of FL degradation, including destruction of the aromatic skeleton structure and the formation of amorphous carbon and graphite. The MC remediation method was applied to FL contaminated soil, showing that FL was efficiently degraded in soil without any soil additives, resulting in a significant reduction in the biotoxicity of the remediated soil. The organic matter, moisture content and pH of the actual soil changed slightly after mechanical ball milling. Thus, the MC method has high potential in the remediation of PAH-contaminated soils. HIGHLIGHTS A mechanochemical (MC) method for the degradation of fluoranthene was assessed. The use of silica and kaolin as soil additives enhances fluoranthene remediation. Fluoranthene can be efficiently removed from contaminated soil by milling alone. The degradation mechanism was skeleton structure destruction and carbonization. The biotoxicity of soil was significantly reduced by milling.

Wu, Lisha; Khodadoust, Amid P.; Punia, Snover

doi: 10.1080/09593330.2021.2024272pmid: 35042451

A manganese coated sand (MCS) sorbent containing manganese (II,III) oxides was developed for adsorption and transformation of chromium [Cr(VI) and Cr(III)] with potential application in flow-through permeable media adsorption filters. Characterization of the MCS sorbent using XRD and XPS showed that the oxides of manganese (II) and manganese (III) were present on the MCS sorbent surface. Adsorption of both Cr(VI) and Cr(III) onto the MCS sorbent occurred over a broad pH range from 3 to 10. Surface charge analysis of the MCS sorbent determined a pHPZC of 7.8, which may facilitate the uptake of both oxy-anionic Cr(VI) species and cationic Cr(III) species. Favorable adsorption of Cr(VI) and Cr(III) onto the MCS sorbent occurred according to the Langmuir and the Freundlich adsorption equations, with a higher adsorption capacity for Cr(III) than Cr(VI). Adsorption parameters from the Langmuir, the Freundlich and the Temkin adsorption equations showed a stronger binding of Cr(VI) than Cr(III). Adsorption of Cr(III) decreased with increasing calcium concentration while adsorption of Cr(VI) decreased with increasing concentration of common anions found in natural water in the following order: phosphate > sulfate> bicarbonate. Transformation of chromium occurred on the surface of the MCS sorbent due to the partial reduction of Cr(VI) and the partial oxidation of Cr(III), which may be attributed to the role of surface manganese (II,III) oxides as either reducing or oxidizing agents. The MCS sorbent is a recyclable and sustainable adsorbent for removal of chromium from water with an environmental impact comparable to ion-exchange technology.

Wei, Shuxia; Chen, Wu; Li, Zhili; Liu, Zhuozhuang; Xu, Ao

doi: 10.1080/09593330.2021.2024274pmid: 34962213

In the present study, we synthesized a cationic lignosulfonate hydrogel (LS-g-P (AM-co-DAC)) by grafting acrylamide (AM) and acryloxyethyl trimethyl ammonium chloride (DAC) onto sodium lignosulfonate (LS) via free radical copolymerization. The solution pH, contact time, initial concentration, and temperature were comprehensively investigated through the static adsorption method for the adsorption behaviours of Cr(VI) by the hydrogel. The experimental results show that the best conditions were a temperature of 30°C, a dosage of 0.1 g, pH = 3, a concentration of 50 mg / L, and contact time = 2 h with removal efficiencies of above 70% and adsorption capacity of 18.14 mg·g−1. The adsorption process followed the Langmuir isothermal model, indicating monolayer adsorption, and the maximum adsorption capacity was 58.86 mg·g−1. Adsorption kinetics results show that the pseudo-second-order kinetic model dominated the adsorption process, and the adsorption activation energy was 5.489 kJ·mol−1. In addition, the adsorption involved spontaneous exothermic and entropy reduction. The combination of FT-IR, SEM, and XRD was used to characterize the structure and properties of the prepared hydrogel, and the adsorption mechanism was the result of electrostatic attraction, physical and chemical adsorption, and hydrogen bond. The hydrogel has good regenerative properties after desorption. Overall, this work synthesized an environmentally friendly biomass lignin-based hydrogel, which can be used as an adsorbent for the treatment of anionic pollutants, and explored a new method for the high-value utilization of industrial lignin. Highlights Novel cationic lignosulfonate hydrogel (LS-g-P (AM-co-DAC)) was synthesized by a free radical method. SEM and XRD results confirmed the surface of the obtained hydrogel shows a 3D network structure and does not have a crystal structure. LS-g-P (AM-co-DAC) hydrogel adsorbent can selectively adsorb Cr6+ at pH 3.0. The adsorption conditions and the adsorption mechanism were studied in detail. Electrostatic interaction plays a key role in the adsorption of Cr6+.

Amin, Muhammad; Yousuf, Masarrat; Attaullah, Mohammad; Ahmad, Naveed; Azra, Mohamad Nor; Lateef, Mehreen; Buneri, Islam Dad; Zekker, Ivar; El-Saber Batiha, Gaber; Aboelenin, Salma Mostafa; Zahoor, Muhammad; Ikram, Muhammad; Naeem, Muhammad