In this work, hexavalent chromium adsorption onto LDPE and agave fiber composites coated with chitosan or cellulose was studied in batch experiments. Chemical modifications consisting in cross-linked chitosan, cross-linked chitosan xanthate, and cellulose xanthate were applied to the polysaccharide-coated sorbents in order to increase their stability and adsorption capacity. The sorbents were characterized in terms of morphology by scanning electron microscopy and their chemical composition was evaluated by infrared and nuclear magnetic resonance spectroscopies. The results showed that the adsorption kinetics followed the pseudo-second-order model in all cases (i.e., chemisorption as the rate-limiting step of the adsorption reaction). Moreover, the isotherms evidenced a monolayer adsorption on homogeneous sites described by the Langmuir model. The maximum adsorption capacity of 284.7 mg Cr(VI)/g was obtained for the cross-linked chitosan xanthate sorbent at pH 4 which represents an increase of 43% against the chitosan-coated sorbent (199.1 mg Cr(VI)/g). Besides, functionalized cellulose sorbent also increased its capacity from 84.5 to 106.0 mg Cr(VI)/g cellulose due to the xanthate group. Up to six adsorption-desorption cycles were completed for the case of functionalized chitosan sorbent, confirming that the stability was increased with the cross-linking and the material could be reused several times without losing its adsorption capacity. In the case of cellulose xanthate, only three adsorption cycles were completed. However, improvements were observed in the desorption capacity considering that it decreased below 20% after two cycles in the cellulose-coated sorbent.

A challenge in side-stream treatment of anaerobic digester supernatant is that the effluent does not meet discharge standards. To address this challenge, this study tested tubular multichannel ceramic microfiltration (MF) and ultrafiltration (UF) membranes for the post-treatment of anaerobic digester supernatant. Pollutant rejection (total suspended solids (TSS), COD, total nitrogen (TN), and total phosphorus (TP)), color removal, and membrane susceptibility to fouling were determined at various transmembrane pressures (TMPs) (0.2, 0.3, 0.4, 0.5 MPa). Both methods completely removed TSS. In MF, COD was removed with 48–76% efficiency at 0.2–0.4 MPa. In UF, COD removal efficiency was slightly higher, reaching 83.7% at 0.4 MPa. With both methods, pollutant removal did not increase at TMP of 0.5 MPa. With both MF and UF, color was reduced by 54–100%, irrespective of the TMP. At 0.2–0.4 MPa, membrane resistance was lower and permeate flux was much higher with MF than UF. At 0.5 MPa, the methods differed only slightly from each other. Due to the larger cut-off, flux decline was slower in MF (0.7 h⁻¹) than in UF (1.1 h⁻¹), as the larger pore-size favors less foulant deposition. Thus, taking into account rejection efficiency, capacity, washing frequency, and cost (pressure), these results indicate that MF at 0.4 MPa is the most effective variant for post-treatment of anaerobic digester supernatant. With this variant, the almost colorless permeate contained 25 mg COD/L, no TSS, 55 mg TN/L (75% in the form of nitrites and nitrates), and 8.5 mg TP/L, thus meeting criteria for water to be used in irrigation or algae cultivation.

Soil contamination with polychlorinated biphenyls (PCBs) is one the most relevant environmental problem in the SIN (Site of National Interest) of Taranto (Apulia Region, Southern Italy) and the surrounding area. Evaluation of PCB contents and their spatial distribution is an essential pre-requisite for soil remediation. Conventional laboratory analyses, although useful and irreplaceable for a precise and detailed evaluation of these contaminants, are costly and time-consuming, thus not very suitable for investigation over large areas. Then, there is a need to develop/validate alternative, rapid and cost-effective techniques, to use as substitutive of integrative to conventional analytical approaches. In this study, the usefulness of soil colour, based on spectrometric measurements, coupled with regression analysis, was assessed. Until now, never an analogous investigation has been realised. Twenty-eight soil samples, previously collected within an area (the ex-MATRA) highly contaminated by the disposal of oil used as dielectric fluid, composed by a mixture of PCB congeners, were used in the investigation. Colour coordinates in different colour systems were calculated from spectroradiometric measurements over the soil samples. Eighteen PCB congeners (i.e. 12 dioxin-like PCBs and six non-dioxin-like “indicator” PCBs), their sum (PCBs₁₈) and the extractable organic halogen content (EOX)—which is an expression of the total content of halogen in organochlorine compounds, including the PCBs—were determined through conventional laboratory analysis. Simple linear regression analysis was carried out to predict the values of PCBs and EOX on the basis of colour variables. Excellent predictive models (R² > 0.80) for PCBs₁₈ and EOX, as well as for some of the individual PCB congener, resulted from the regression analysis. Thus, spectroscopic determination of soil colour can be considered as a promising tool for a rapid screening of PCBs in contaminated soils.

Excess nitrogen in the ecosystem could result in eutrophication and harmful algal bloom in an ecosystem. Low impact development (LID) facilities, regarded as an integral part of green infrastructures for flow control and water quality management may include, but are not limited to, dry/wet ponds, green roof, bioswale or linear ditch, vegetated natural strip, exfiltration trench, piping networks with underdrain or reuse options, and bioswale. This study presents a new approach using a linear ditch along a roadside for LID with the aid of two green sorption media that are designed for co-treatment of stormwater and groundwater for nutrient removal. The stormwater is primarily from agricultural discharge and transportation stormwater runoff. Two recipes of green sorption media, including the green sorption media and woodchip, were examined and compared through a laboratory-scale column study and a field-scale test bed media under various influent concentrations and flow conditions. The green sorption media were found more appropriate than the woodchip media for field-scale applications because the green sorption media may exhibit long-standing microenvironments and hydraulic patterns to provide a homogeneous hydraulic retention time and infiltration rate for nutrient removal. Therefore, such a new LID practice may not only mitigate the impact from various surface stormwater runoffs but also co-treat groundwater and stormwater for nutrient removal.

Particle-induced x-ray emission (PIXE) spectroscopy has been used to characterize soil samples from two relatively old gold mine sites (Iperindo and Itagunmodi) in the Ilesha schist belt of Southwestern Nigeria. This is with a view to identifying the indicator or pathfinder elements of gold for fingerprinting and toxicity potential assessment purposes. Average elemental concentrations of 19 major, minor, and trace elements were determined, and the geochemical data of Mn, Ni, Cu, Zn, Ag, As, Pb, and Au together with multivariate factor and cluster statistical analyses allowed to identify As and Ag as the pathfinder elements of gold. The high concentration of the determined pathfinder elements (As and Ag) as well as other toxic metals (Pb and Cu) implies a relatively high metal contamination risk to the miners and the ecosystem. The major hazard is represented by the abandoned mining wastes, pits, and ponds, already serving as fish ponds.

Biological materials play a significant role in the treatment of heavy metal-contaminated soil and wastewater. In this study, the Pb²⁺ biosorption potential of lichen Evernia prunastri, extensively available at a forest in Bilecik-Turkey, was investigated at batch-scale level. The optimal conditions were determined and the adsorption isotherms, kinetics, and thermodynamic calculations were also done. In order to have detailed knowledge about metal biosorption, SEM, FTIR, and BET analyses were carried out before and after the biosorption process. The optimal pH was found pH 4 and the maximum metal uptake capacity was found as 0.067 mol kg⁻¹. The results of this study indicate that the lichen was effectively applied to the removal of Pb²⁺ process as an inexpensive biosorbent from industrial wastewater.

In this study, we attempt to prospect potential bacterial isolates from mangrove sediments of Mangalavanam, Kerala, India, with positive carbonic anhydrase (CA) activity to sequester carbon dioxide by calcium precipitation process. Fifteen bacterial colonies (M1–M15) isolated were screened for their carbonic anhydrase enzyme production potential based on p-nitro phenol acetate assay. Based on the secondary screening, M3 and M8 were identified as the most potential for carbonic anhydrase production. The specific activity of the partially purified CA enzyme from M3 and M8 were 44 U mg⁻¹ and 76 U mg⁻¹ respectively. The enzyme activity increased by 1.6-fold upon precipitation by acetone (80%). The potential isolate which higher CA production, M8 was identified as Bacillus altitudinis based on 16S rDNA sequencing. Soil microcosm was established to study carbonic anhydrase production and CO₂ sequestration ability of B. altitudinis M8 strain. B. altitudinis M8 strain could reduce CO₂ by 75 ± 0.12% in microcosm composed of sterilized soil with bacteria (SSB) and by 97 ± 0.34% in microcosm with sterile soil with enzyme (SSE). Hence, the application of enzyme was found to be more effective in removing CO₂ when compared to bacterial inoculum. To further understand the bio-mineralization ability of this microbial isolate, calcium precipitation assay was conducted. There was a reduction of 42.22 ± 0.23% of free calcium in the medium through calcite precipitation. The carbonic anhydrase-mediated calcium precipitation by B. altitudinis M8 strain could be effectively employed in the process of carbon dioxide sequestration.

Due to its unique properties, the potential application of graphene oxide (GO) in treating environmental pollution has attracted wide attention. In this study, the UV-light catalyzed photoreduction of Cr(VI) by GO was assessed as well as its adsorption toward Cr(VI), and FTIR and XPS techniques were adopted to reveal the underlying mechanisms. The surfaces of GO were negatively charged across the pH range examined. Therefore, the increase in pH resulted in the decrease in Cr(VI) adsorption due to the enhancement in repulsion between Cr(VI) and GO surfaces. The kinetic studies showed that the Cr(VI) adsorption proceeded quickly during the 0–24 h stage, followed by a slow process until to the end of reaction (96 h). Additionally, the kinetic data could be properly described with the pseudo-first-order rate equation (R² = 0.9754). With the UV-light irradiation, Cr(VI) reduction in the presence of 0.5 g L⁻¹ GO was observed with the concentration of Cr(VI) decreased from 0.1 mM to zero within 12 h at pH 3.0, while which would be suppressed as the pH increased. The addition of EDTA could enhance the photocatalytic Cr(VI) reduction due to the consumption of the photogenerated holes (h⁺), leaving more Cr(III) species present in solution. The generation of h⁺ was further confirmed by the complete photodegradation of 4-CP during 48 h. Moreover, the changes in FTIR and XPS spectrum of GO before and after reaction indicated the oxidization of epoxy and hydroxyl groups by holes or reduction by electrons was involved in the photoreaction. The photoreduction of Cr(VI) could was also observed in an oxisol with the existence of GO, with the disappearance of 0.1 mM of aqueous Cr(VI) at pH 4.40 after 36 h. The results above could enhance our understanding on the essence of photoreactivity of GO, and indicated that the potential release of GO into soil environments would be helpful to eliminate the risk posed by Cr(VI) through the UV-light irradiated photocatalytic reduction.

This research aims to study the effect on industrial carbon intensity by decomposing electricity consumption into electricity consumption volume and electric power intensity by using panel data of 27 China’s manufacturing sectors. An improved STIRPAT model is also developed by this article to identify the unexplored potential influencing factors. The research findings suggest that there exists a long-run equilibrium relationship between electricity consumption and carbon intensity and unidirectional causality from electricity consumption volume to carbon intensity. Regression results indicate that electricity consumption volume has a significantly negative effect on industrial carbon intensity for the full sample. However, due to the significantly positive influence that electric power intensity has on carbon intensity, we conclude that energy consumption and industrial economy failed to achieve the decoupling effect. The impacts of electricity consumption volume and electric power intensity have industrial heterogeneity. Electric power intensity impacts carbon intensity the most for resource intensive sectors. The effects of subgroups are further examined for sectors with high/low carbon emission volume and carbon intensity. Foreign direct investment (FDI) is conducive to reducing carbon intensity for sectors with high volume and sectors with high intensity. Industrialization level demonstrates a significantly positive effect on improving carbon intensity for sectors with low volume and sectors with low intensity. Finally, we put forward specific suggestions on the basis of these empirical findings.