Numerous carbon dioxide mineralization (CM) processes have been proposed to overcome the slow rate of natural weathering of silicate minerals. Ten of these proposals are mentioned in this article. The proposals are described in terms of the four major areas relating to CM process design: pre-treatment, purification, carbonation, and reagent recycling operations. Any known specifics based on probable or representative operating and reaction conditions are listed, and basic analysis of the strengths and shortcomings associated with the individual process designs are given in this article. The processes typically employ physical or chemical pseudo-catalytic methods to enhance the rate of carbon dioxide mineralization; however, both methods have its own associated advantages and problems. To examine the feasibility of a CM process, three key aspects should be included in the evaluation criteria: energy use, operational considerations as well as product value and economics. Recommendations regarding the optimal level of emphasis and implementation of measures to control these aspects are given, and these will depend very much on the desired process objectives. Ultimately, a mix-and-match approach to process design might be required to provide viable and economic proposals for CM processes.

Powdered activated carbon/ultrafiltration (PAC/UF) hybrid process was investigated for removing from wastewater five pharmaceutical and personal care products (PPCPs): 1-H-benzotriazole, DEET, chlorophene, 3-methylindole and nortriptyline-HCl. Adsorption, UF and PAC/UF experiments were performed, focusing on PPCP adsorption as a function of PPCP characteristics and organic matter (EfOM) competition. Two water matrices and two fine-particle PACs were studied, differing on EfOM nature and concentration and on PAC microporosity. Neutral PPCP uptake by the positively charged, meso- and microporous PACs followed PPCP hydrophobicity expressed by log Kₒw. The uptake of the positively charged nortriptyline exceeded the expected from log D due to its high aromaticity and the background ions, which partially shielded PAC-nortriptyline electrostatic repulsions. Adsorption capacity depended on PPCP hydrophobicity whereas the kinetics further depended on PPCP charge. Hydrophobic EfOM was preferentially adsorbed and a stronger competitor, particularly for PPCPs with logKₒw < 2.6. The highly microporous PAC better adsorbed these PPCPs and the hydrophobic EfOM, and it attenuated the EfOM competition. For all waters, PAC had no effect on UF-flux, and it significantly improved PPCP and EfOM removal by PAC/UF over standalone PAC and UF. For all conditions and microcontaminants, PPCP uptake exhibited a sigmoid curve with logKₒw, with a turning point at 2.2–2.6. In real applications, meso- and highly microporous PACs are recommended, and the dose should target the PPCPs with log Kₒw < 2.6.

The stress tolerance of wetland plants is crucial for their appropriate application in constructed wetland (CW). Ammonia, one of the major pollutants in wastewater, is nutrition for plants at low concentrations but could be toxic at excess concentrations. This study aimed to investigate the effect of external ammonia at different concentrations (0, 1, 2, 4, 8, 10 mg L⁻¹) to a specific submerged plant Potamogeton crispus (P. crispus), which has been used widely in CW. Results showed that the threshold value of ammonia for P. crispus was 4 mg L⁻¹, under which no obvious variations from the control group were detected in all associated observations. When ammonia concentration exceeded 4 mg L⁻¹, plants displayed significant increase in lipid peroxidation product contents (MDA, O₂ ⁻ and H₂O₂), antioxidant enzyme activities (T-SOD, POD, and CAT), and a corresponding increase in the percentages of electrolyte leakage. However, external ammonia only had slight effect on the chlorophyll synthesis of P. crispus under the studied concentration range. Excess ammonia exposure (≥4 mg L⁻¹) could affect the physiological responses of P. crispus, by inducing oxidative stress and by limitedly altering permeability of cell membrane and plant photosynthesis. The results of this study supplied useful information for the aquatic vegetation collocation in CW design, and it is suggested to take proper application of P. crispus in CW when treating eutrophication or other relatively heavily polluted water.

Studies on ion movement in soil profiles associated to the application of vinasse are scarce. The objective of this study is to assess the quantity of inorganic and organic ions in the profile of the soil under sugarcane. The study was realized in a commercial sugarcane cultivar in the municipality of Ponta Pora, MS, Brazil in the harvest year of 2010/2011. The soil in the experimental area was classified as Haplorthox clay. The experimental design was randomized blocks, with four repetitions, two depths, and four harvest periods, after application of a 350 m³ h⁻¹ vinasse dosage. Twenty-four soil solution extractors were installed at a distance of 4 × 4 m from each other in the areas under vinasse treatment. Vinasse was chemically characterized by the inductively coupled plasma atomic emission spectrometry method. The extracted solution samples were determined for ionic chromatography. Elevated concentrations of lactic, butyric, citric, tartaric, succinic, formic, and acetic acids were found up to 1 m of depth up to 29 days after application. After 63 days, no traces of those anions were found in the soil. There was a rise in nitrate and a decline in the content of chloride and sulfate.

In earlier studies in the existing literature, concentration balance in the feeding solution has never been considered as an influencing factor when the studies were carried out under several feeding conditions to examine effects of different carbon sources on the enhanced biological phosphorus removal (EBPR) process. For a better understanding of a stable operation of an EBPR reactor, it is thought that effects of the concentration balance need to be combined and evaluated with effects of the type of carbon sources in EBPR studies. Therefore, this study was aimed at determining the effect of concentration balance on the performance stability and the phosphorus and glycogen dynamics of a sequencing batch reactor (SBR). In this study, the SBR operation was divided into two main stages. In the first stage, two different ratios of the total concentration of monovalent (M) to divalent (D) cations (in milliequivalent per liter, meq/L) (7.6 and 1.5, 30 days of operation for each) was applied in the feeding solution to investigate the effect of the concentration balance on the performance stability of the SBR. During this stage, sodium acetate was used as the sole carbon source. To investigate the effect of the type of carbon source on the EBPR process under the condition of constant M/D ratio, sodium acetate was used as the sole carbon source during the first half of the reactor operation of 120 days, and, then, the carbon source was abruptly switched to glucose in the second stage.

This work investigates whether and how salicylic acid (SA) alleviates chromium (Cr) toxicity in rice. Addition of SA under Cr stress markedly increased growth parameters, total protein content, and membrane stability but reduced the concentration and translocation of Cr in shoots but not in roots, suggesting that SA does have critical roles in Cr detoxification associated with Cr sequestration in roots. Further, Fe along with the expression of two Fe transporters (OsIRT1, OsNRAMP1) showed no significant changes in roots due to SA supplementation under Cr stress, indicating that regulation of Fe uptake is not involved in Cr reduction in rice plants through SA. At molecular level, OsPCS1 (phytochelatin synthase) and OsMT1 (metallothionein) and OsHMA3 (P-type ATPase 3) transcripts significantly upregulated following SA supplementation under Cr stress, suggesting that these chelating agents may bind to Cr leading to elevated Cr retention in roots. Furthermore, increased CAT, POD, SOD, and GR leading to decreased H₂O₂ along with elevated metabolites (cysteine, methionine, glutathione, proline, ascorbic acid) in roots implies active involvement of ROS scavenging and plays partial role in SA-mediated alleviation of Cr toxicity in rice plants. These findings will be useful for bioremediation of Cr toxicity in rice and other crops.

The objective of this study was to examine the effect of band gap of photocatalyst on the decolorization of dye new coccine (NC). The concentration of NC in the present of CuO, Fe₂O₃, TiO₂, and ZnO reduced to 50.5, 23.3, 0.1, and 0 mg L⁻¹, respectively, after 5 h solar light irradiation. The concentration of NC in dark condition only decreased to 48.140, 45.079, 35.269, and 31.045 mg L⁻¹ with CuO, Fe₂O₃, TiO₂, and ZnO as photocatalysts, respectively, after 5 h contact time. The absorbance peaks and chemical oxygen demand (COD) concentration of NC in the presence of TiO₂ and ZnO decreased to baseline and zero compared to the CuO and Fe₂O₃. The COD concentration of NC with CuO, Fe₂O₃, TiO₂, and ZnO as photocatalysts reduced to 21, 13, 0, and 0 mg L⁻¹, respectively, after 12 h of solar irradiation. The surface morphology of photocatalysts was examined by scanning electron microscope (SEM), and it was found that the particle size of CuO, Fe₂O₃, TiO₂, and ZnO ranging 250–375, 250–600, 40–100, and 60–500 nm, respectively. In summary, the higher band gap energy level indicated greater photocatalytic degradation and mineralization of NC.

Mine soils often contain high levels of metals that produce serious environmental problems and poor fertility conditions that limit their reclamation. The aim of this study was to evaluate the influence of a compost and biochar amendment on the nutrient phytoavailability in a mine soil from the depleted copper mine of Touro (Spain). For this purpose, a greenhouse experiment was carried out amending the mine soil with increasing proportions (20, 40, 80 and 100%) of the compost and biochar mixture and planting Brassica juncea plants. The results revealed that the mine soil had an extremely acid pH and low fertility conditions and was affected by copper contamination. The addition of compost and biochar to the mine soil increased soil pH values (from 2.7 to 8.7), total carbon (from undetectable values to 149 g kg⁻¹) and total nitrogen (from undetectable values to 11,130 mg kg⁻¹) contents and phytoavailable concentrations of K, Mg, Na and P and promoted plant growth, since B. juncea plants did not survive in the untreated mine soil. The application of amendment decreased the phytoavailable concentration of Al, Co, Cu, Fe and Ni in the soil, resulting in a reduction of copper toxicity. The use of compost and biochar as a soil amendment combined with B. juncea plants could be an efficient strategy for the reclamation of degraded soils with low fertility conditions.

Diesel spills may considerably damage the sensitive coastal wetlands along Huangpu River, Shanghai, China. In this experiment, Cyperus rotundus, a dominant coastal marsh plant, was cultured in diesel-contaminated soils at concentrations of 0, 1000, 5000, 10,000, 15,000 and 20,000 mg kg⁻¹ to investigate its phytoremediation potential. In this study, plant biomass, removal characteristic of diesel, redox potential, and activities of urease, dehydrogenase, and polyphenoloxidase in soils were determined after 50-day pot experiments. The results demonstrated that soils planted with Cyperus rotundus had significantly less diesel than did unplanted soils. The residual concentrations of alkanes in soils at 10,000 mg kg⁻¹ after 50 days showed that 52.9–92.0 % of Fraction a (C₁₄–C₁₉) and 47.8–64.4 % of Fraction b (C₂₀–C₂₇) were removed in unplanted soils, while more than 90 % of both Fractions a and b were removed in planted soils. The peak value of urease and dehydrogenase activities was at 15,000 mg kg⁻¹ of diesel-contaminated concentration; however, the peak value of polyphenoloxidase activity appeared at 10,000 mg kg⁻¹. It was deduced that the diesel concentration between 10,000 and 15,000 mg kg⁻¹ might be a limit which Cyperus rotundus could tolerate diesel pollution.

Combination of active and thermally stable amino acid-functionalized ionic liquids (AAILs) with high surface area and porosity of mesocellular silica foams (MCF) to form a robust CO₂ sorbent is investigated in this study. These sorbent composites (MCF-x) are synthesized by immobilizing three AAILs (Gly, Lys, and Arg) into MCF by a simple wet-impregnation method. The prepared AAILs and MCF-x sorbents are characterized by N₂ adsorption/desorption, small-angle X-ray scattering (SAXS), elemental analysis (EA), and Fourier-transformed infrared (FTIR) spectroscopies. Their corresponding CO₂ sorption–desorption performance at 348 K under ambient pressure using dry 15 % CO₂ is also studied. The obtained results show that the AAILs have low CO₂ sorption capacities and rates because of their high viscosities. The MCF-x sorbents, however, exhibit remarkable enhancement of sorption capacities and fast kinetics. Among these sorbents, MCF-Lys possesses the superior sorption capacity of 1.38 mmolCO₂/gₛₒᵣbₑₙₜ, the higher tolerance to water moisture and much better long-term durability which may be a promising sorbent for CO₂ capture applications.