Uranium wastewater treatment has been performed by adsorption method using Mg(OH)₂-impregnated activated carbon. Research purposes are to determine (i) uptake capacity of the adsorption isotherm of uranium in Mg(OH)₂-impregnated activated carbon, (ii) mathematical correlation of uranium (VI) adsorption rate, and (iii) effect of the impregnation ratio of adsorbent to uranium removal efficiency. Adsorbent was synthesized through several stages, i.e., pyrolysis of coconut shell (400 °C), chemical activation using NaOH, and impregnation process using varied solutions of MgCl₂ (600 °C). The materials were characterized comprehensively using FTIR, BET, XRF, and XRD. The parameters studied in this research were adsorption temperature (T), average particle diameter of adsorbent (d), mass ratio of adsorbent to wastewater solution (r), and impregnation ratio of Mg(OH)₂/activated carbon. The results shown that equilibrium data are well fitted with the Langmuir isotherm model with the maximum adsorption capacity about 85 mg/g at 303 K and dimensionless constant separation factor (RL) value about 0.7. The adsorption rate was increased by increasing the adsorption temperature, mass ratio of adsorbent to wastewater solution, and the decrease of particle diameter of adsorbent with mathematical equation of the uranium (VI) adsorption rate as:[Formula: see text]In addition, the results also shown that increasing the impregnation ratio from 0.3 to 1.0 can increase the uranium removal efficiency up to 67.3%.

The effect of two freezing treatment methods, combined ultrasonic freezing and conventional freezing, on secondary municipal wastewater sludge particle size, and the relationship between particle size and soluble organic matter, and dewatering characteristics (filterability and settleability) were examined. Quantitative analysis was carried out to determine the change in sludge particle sizes and the correlation coefficients between particle size and sludge volume index (SVI), capillary suction time (CST), and soluble chemical oxygen demand (sCOD) following freezing treatments. Freezing treatments significantly increased sludge median particle size (d50) to 4 to 5 times of the control, and d10 and d90 increased by 3 to 4 times. The correlation coefficients indicated that both freezing treatment methods were able to simultaneously enhance dewaterability and soluble organic matter (sCOD). Comparisons of the test results of the two freezing methods, as well as freezing methods with other treatment methods examined (ultrasound, thermal, and microwave) were conducted. The relationship between particle size and dewaterability remained constant across all treatment methods with increase in particle size correlated to improved dewaterability while the correlation of particle size and soluble organic matter seemed to depend on the treatment methods.

Pistia stratiotes is a common aquatic plant of the northern region of the state of Rio de Janeiro, and its use as adsorbent material was studied in the present work. The preparation process included washing, drying, grinding, and acid activation. The sorption potential for removal of the indigo carmine dye from aqueous solutions was tested under various conditions, such as initial concentration, contact time, and temperature. The tests showed that the obtained biosorbent showed good performance for dye removal with a maximum capacity of 41.2 mg/g. The kinetic studies revealed that the pseudo-second-order equation provided the best fit of the experimental data. The Freundlich isotherm provided the best fit of the experimental sorption data for the system under study. The results obtained show that Pistia stratiotes has great potential to be used as biosorbent for the removal of dyes from aqueous solutions.

Polycyclic aromatic hydrocarbons (PAHs) upset the basic biological parameters of the soil, such as enzymatic activity, which can be used to identify the direction and intensity of organic and mineral substance transformation in the soil environment. The aim of this study was to determine the impact of soil contamination with naphthalene, phenanthrene, anthracene and pyrene at rates of 0–4000 mg kg⁻¹ DM (dry matter) of soil on the activity of acid phosphatase and alkaline phosphatase. An analysis was also conducted on how some organic substances, such as cellulose, sucrose and compost at rates of 0 and 9 g kg⁻¹ DM alleviate the PAH impact on the enzymes under study. The experiment was carried out in a laboratory with loamy sand as the soil material. Phosphatase resistance (RS) and soil resilience (RL) were calculated. The enzyme activity was found to depend significantly on the PAH rate, time of PAH deposition in soil and the type of organic substance added to the soil. The activity of acid and alkaline phosphatase increased with the degree of soil contamination with PAHs. Naphthalene had the greatest stimulating effect on enzyme activity. Biostimulation of soil with cellulose, sucrose and compost had a positive effect on acid and alkaline phosphatase activity, with cellulose and compost being the most effective in boosting acid and alkaline phosphatase activity, respectively. Naphthalene had the greatest effect on acid and alkaline phosphatase resistance and pyrene had the least effect. Low RL indices indicate that the presence of PAHs permanently disturbed the activity of acid and alkaline phosphatase.

Municipal solid waste incineration (MSWI) generates bottom ash, fly ash (FA), and air pollution control (APC) residues as by-products. FA and APC residues are considered hazardous due to the presence of soluble salts and a high concentration of heavy metals, and they should be appropriately treated before disposal. Physicochemical characterization using inductively coupled plasma mass spectroscopy (ICP-MS), X-ray diffraction (XRD), and X-ray fluorescence (XRF) have shown that FA and APC have potential for reuse after treatment as these contain CaO, SiO₂, and Al₂O₃. Studies conducted on treatment of FA and APC are categorized into three groups: (i) separation processes, (ii) solidification/stabilization (S/S) processes, and (iii) thermal processes. Separation processes such as washing, leaching, and electrochemical treatment improve the quality and homogeneity of the ash. S/S processes such as chemical stabilization, accelerate carbonation, and cement solidification modify hazardous species into less toxic constituents. Thermal processes such as sintering, vitrification, and melting are effective at reducing volume and producing a more stable product. In this review paper, the treatment processes are analyzed in relation to ash characteristics. Issues concerning mixing FA and APC residues before treatment, true treatment costs, and challenges are also discussed to provide further insights on the implications and possibilities of utilizing FA and APC as secondary materials.

Phytoplankton assemblages were investigated in 2015 along the seasonal changes of the Genhe River in the Greater Hinggan Mountains. The survey was performed in June (spring), August (summer), and October (autumn) at nine sampling stations to study the community composition, abundance, and biodiversity. The results showed that 61 species belonging to 16 genera were identified, including Bacillariophyta of 31 species, Dinophyta 2 species, Cyanophyta 2 species, Chlorophyta 20 species, Chrysophyta 2 species, and Cryptophyta 1 species; Besides, Bacillariophyta are dominant species. Shannon-Wiener (H′) and Pielou (J′) indices indicated that phytoplankton community was stable. And these two indices were significantly lower in summer than in spring and autumn. Phytoplankton abundance and biomass show significant differences in each season. The total phytoplankton abundance (1122.3 × 104 ind/L) and biomass (6.5709 mg/L) in summer are much higher than that in spring and autumn. There were few species and low abundance and biomass in the upper reaches of Genhe River; this fact can be explained by the cold climate in the Greater Higgnan Mountains region. Canonical correspondence analysis (CCA) was used to analyze the data. It revealed that Fe³⁺, Cu²⁺, pH, and water temperature (WT) were responsible for most of the variation in space in the phytoplankton community. These environmental parameters play an essential role in the community structure variation of phytoplankton in the upper reaches of Genhe River, the strong association between phytoplankton community structure and ecological factors is varied in each season.

Magnetic Fe₃O₄ assembled on nanoscale zero-valent iron (nZVI) supported on an activated carbon fiber (ACF) to form nanoscale magnetic composites (nZVI-Fe₃O₄/ACF) for removing Cr(VI) and Cu(II) from aqueous solution through a permeable reactive column was synthesized via an in situ reduction method. The nZVI-Fe₃O₄/ACF composites and the interaction between nZVI-Fe₃O₄/ACF and both Cr and Cu ions were characterized by field emission scanning electron microscopy (FESEM) with EDX, TEM, XRD, and XPS. Batch experiments were used to analyze the effects of main factors on Cr(VI) removal and investigate the simultaneous removal of Cr(VI) and Cu(II) through a permeable reactive column. The results indicated that the ACF and Fe₃O₄ can inhibit the agglomeration and enhance the dispersibility of nZVI, and Fe₃O₄ and nZVI displayed good synergetic effects. The removal efficiency of Cr(VI) improved with the increase amount of Fe₃O₄ in the nZVI-Fe₃O₄/ACF composites. With low initial concentration of Cr(VI) and acidic conditions, ~ 90% of 20.0 mg·L⁻¹ Cr(VI) in the solution was removed after 60 min. The removal of Cr(VI) was also affected by coexisting ions. The removal efficiency of 10.0 mg·L⁻¹ Cu(II) was ~ 100% after 45 min of reaction, and the presence of Cu(II) can accelerate the reduction of Cr(VI). The simultaneous removal mechanisms of Cr(VI) and Cu(II) by the nZVI-Fe₃O₄/ACF composites also were proposed.

Nitrogen removal by anammox process has been recognized as efficient, cost-effective, and low-energy alternative removal. The longer start-up periods of anammox process hindered the widespread application of anammox-based technology. In this study, four identical unplanted subsurface-flow constructed wetlands (USFCWs) were built up to investigate the effects of electron acceptors (Fe³⁺, Mn⁴⁺, SO₄²⁻) on the start-up of anammox process. Results indicated that the start-up time of anammox process was shortened to 105 days in R1 (with Fe³⁺ addition) and 110 days in R2 (with Mn⁴⁺ addition) with nitrogen removal efficiencies of above 75%, compared with 148 days in R0 (control). The addition of SO₄²⁻ had no significant effect on start-up process. High-throughput sequencing results demonstrated that Shannon index increased significantly from 2.87 (R0) to 5.08 (R1) and 5.00 (R2), and the relative abundance of Candidatus Anammoxoglobus rose from 3.6 to 5.3% in R1. Denitratisoma increased significantly in R2 under addition of Mn⁴⁺, which was beneficial for the occurrence of anammox process. The functional genes that related to signal transduction mechanisms and secondary metabolite biosynthesis, transport, and catabolism were upregulated after addition of electron acceptors. These results demonstrated that adding electron acceptors Fe³⁺ or Mn⁴⁺ could be an effective way to accelerate the start-up of anammox process. Graphical abstract ᅟ

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO₂/UV-A, H₂O₂/UV-A, and TiO₂/H₂O₂/UV-A, using sunlight and artificial irradiation. While using TiO₂ in suspension, best results were found at [TiO₂] = 0.1 g L⁻¹. H₂O₂/UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO₂/UV-A and H₂O₂/UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H₂O₂/UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO₂-photocatalysis.

Finding chromium-accumulating plants is of great interest for phytoremediation of soil contaminated by chromium (Cr). Inspired by Traditional Chinese Medicine, we examined the Cr-resistance and Cr-accumulation of Lonicera japonica Thunb. After a two-phase study using both soil and water culture, we found that L. japonica could be a novel Cr-accumulating plant, which contains an average Cr(III) content of 1297.14 mg.kg⁻¹ in its leaves. The Cr enrichment factor and the Cr transport coefficient of Lonicera japonica was 5.19 and 1.79, respectively. Lonicera japonica is the fifth Cr-accumulating plant discovered worldwide, and the first Cr-accumulating woody plant ever discovered. The results support the conclusions drawn from studies of Cr-accumulating Leersia hexandra that oxalic acid production can increase Cr tolerance whereas citric acid or malic acid has no effect, suggesting that oxalic acid might be a common reason for Cr tolerance in all Cr-accumulating plants. Moreover, this study revealed that the production of anthocyanin and carotene can also increase Cr(III) tolerance, suggesting that anthocyanin and carotene might also account for Cr tolerance in Cr-accumulating plants. We believe that the discovery of Lonicera japonica as a Cr-accumulating plant will offer great opportunities in phytoremediation, and the success should be a strong sign that Traditional Chinese Medicine harbors more secrets to be uncovered with modern science.