This study addressed the removal performance of RR2 from aqueous solutions in adsorption columns experiments by comparing the potential of activated carbon alone (ACA) and microbially inoculated (MIAC), prepared from barks of a largely available tree in Brazilian Cerrado biome, Hymenaea courbaril L. or “Jatobá,” presenting the kinetics, isotherms, breakthrough curves, and dissolved organic carbon removal. ACA presented strong interaction to RR2 dye, evidenced at the first 20 min when absorbance already attained 66.4%. The removal percentage gradually increased with time and the equilibrium occurred around 91.7% within 120 min. Langmuir model best fitted the isotherm data, indicating a maximum adsorption capacity of 4.068 mg g⁻¹ for the amount of 0.5 g of adsorbent. The Langmuir’s model parameters KL, RL, and R² corresponded to 0.0234 L mg⁻¹, 0.4159, and 0.9663, respectively, indicating a favorable adsorption process (0 < RL < 1). The experiments in adsorption columns revealed maximum adsorption capacities of 14.38 and 11.43 mg g⁻¹ for MIAC and ACA, respectively, where the microbial activity favorably retarded the adsorption breakpoint in approximately 20 min and enhanced the RR2 consumption in 25.8%. Effectiveness of DOC removal attained above 90% for both ACA and MIAC, reducing the content from 86.1 to 7.84 mg L⁻¹ and 4.82 mg L⁻¹, respectively.

The Rhodamine B adsorption was realized in batch using calcined bentonite clay. The effects of Rhodamine B initial concentration, pH, and temperature were evaluated and the conditions where the adsorption was favored were in 500 mg L⁻¹, pH 3, and 35 °C. The equilibrium isotherms studied were from Langmuir and Freundlich. The coefficients of determination (R² > 0.99) were found to confirm the best fitted to Langmuir isotherm, with a monolayer adsorption capacity (qₘₐₓ) of 552.49 mg g⁻¹. The kinetic data agreed well with the pseudo-second order model (R² > 0.99). The in natura and calcined clay were characterized by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ physisorption (BET), and scanning electron microscopy (SEM). Thermodynamic parameters including Gibbs free energy (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were calculated to estimate the nature of Rhodamine B adsorption in clay. The results suggested that the adsorption was endothermic and spontaneous, with the enthalpy adsorption increasing with the increase of temperature. Therefore, calcined bentonite can be used as an efficient adsorbent for discoloration of large volume of residual water, presenting low-cost and high adsorptive capacity.

Graphene oxide (GO) was synthetized from graphite oxidation via the modified Hummers method. Afterwards, the GO was functionalized with diethylenetriamine (DETA) and FeCl₃ to obtain the novel amino-iron oxide functionalized graphene (GO-NH₂-Fe₃O₄). FTIR, XRD, SEM with EDX, and Raman spectroscopy were performed to characterize both GO and GO-NH₂-Fe₃O₄. The GO-NH₂-Fe₃O₄ was then evaluated as adsorbent of the cationic dye Methylene Blue (MB); analysis of the point of zero net charge (pHPZC) and pH effect showed that the GO-NH₂-Fe₃O₄ pHPZC was 8.2; hence, the MB adsorption was higher at pH 12.0. Adsorption kinetics studies indicated that the system reached the equilibrium state after 5 min, with adsorption capacity at equilibrium (qₑ) and kinetic constant (kS) of 966.39 mg g⁻¹ and 3.17∙10⁻² g mg⁻¹ min⁻¹, respectively; moreover, the pseudo-second-order model was better fitted to the experimental data. Equilibrium studies showed maximum adsorption capacity of 1047.81 mg g⁻¹; furthermore, Langmuir isotherm better fitted the adsorption. Recycling experiments showed that the GO-NH₂-Fe₃O₄ maintained the MB removal rate above 95% after 10 cycles. All the results showed sorbent high adsorption capacity and outstanding regeneration capability and evidenced the employment of novel GO-NH₂-Fe₃O₄ as a profitable adsorbent of textile dyes.

Three different types of zirconium-modified bentonites (ZrMBs) including zirconium-modified original bentonite (ZrMOB), zirconium-modified magnesium-pretreated bentonite (ZrMMgB), and zirconium-modified calcium-pretreated bentonite (ZrMCaB) were synthesized and used as active covering materials to suppress the release of phosphorus (P) from sediments. To assess the covering efficiency of ZrMBs to inhibit P release from sediments, we examined the impact of ZrMB covering layer on P mobilization in sediments at different depths as well as the release of P through the interface between sediment and overlying water (SWI) by use of simulating P release control experiments and diffusive gradients in thin films (DGT) technology. The results showed that the amount of soluble reactive P (SRP) in the overlying water greatly decreased after covering with ZrMBs. Moreover, both pore water SRP and DGT-liable P (DGT-P) in the top sediments decreased after capping with ZrMBs. An obvious stratification of DGT-P was observed along the vertical direction after covering with ZrMBs, and static and active layers were found in the top sediment and in the lower sediment directly below the static layer, respectively. Furthermore, ZrMB covering led to the change of P species from easily released P to relatively or very stable P, making P in the top sediment more stable compared to that without ZrMB covering. Besides, an overwhelming majority of P immobilized by ZrMBs is hard to be re-released into the water column in a common environment. Overall, the above results demonstrate that sediment covering with ZrMBs could effectively prevent the transport of SRP from sediments into the overlying water through the SWI, and the control of P transport into the overlying water by ZrMB covering could be mostly due to the immobilization of pore water SRP, DGT-P, and mobile P in the top sediment by ZrMBs.

This study analyzed the performance of organophilic clays obtained from the chemical modification of sodium bentonite clay when applied to the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Kinetic curves and equilibrium isotherms were obtained in order to determine time and adsorption capacity of the material, as well as understand the mechanisms involved in this phenomenon. The results showed that the most predictive kinetic model for experimental data was of pseudo-second order (R² > 0.98), and that external mass transfer is the dominant factor in the time of operation. Isotherms were obtained at temperatures of 298, 308, and 318 K, under which the Dubinin-Radushkevich model was shown to have a good fit to data (R² > 0.96), according to mathematical adjustments. The maximum adsorption capacity obtained experimentally was 50.36 mg g⁻¹, found at a temperature of 298 K, being higher or compatible with other materials reported in the literature. With help of the thermodynamic studies on the process, it was observed that the adsorption of 2,4-D in organophilic clays refers to a spontaneous (ΔG°ₐdₛ < 0), exothermal (ΔH°ₐdₛ = − 9.99 kJ mol⁻¹) process of physical nature. Lastly, it was observed that the adsorbent can be easily regenerated when subjected to eluents such as mixtures containing fractions of ethanol/water (desorption = 95%).

The objective of this work was to analyze four essential oils (EOs) from Rhododendron species in China and evaluate their repellent activity against Tribolium castaneum, Lasioderma serricorne, and Liposcelis bostrychophila adults. These four EOs from Rhododendron species, including R. capitatum, R. przewalskii, R. mucronulatum, and R. micranthum, were obtained by hydrodistillation. Major components of four EOs were identified as sesquiterpenoids by GC-MS. The relatively high components included cedrene (22.20%), borneol (36.64%), 4-(2,3,4,6-tetramethylphenyl)-3-buten-2-one (27.74%), and germacrene D (27.60%). Repellent activity of EOs from Rhododendron species was investigated against T. castaneum, L. serricorne, and L. bostrychophila adults for the first time. In this study, EOs had demonstrated their repellent activities against three stored-product insects in 2- and 4-h exposure. The above results can not only provide comprehensive utilization of plant resources of Rhododendron genus but also establish a very good perspective of novel application to control stored-product insects.

A huge accumulation of domestic waste has caused serious environmental contamination in rural areas of developing countries (RADIC). The characteristics and management of domestic waste are carefully discussed, based on field surveys and a literature review. The results indicate that the generation in most of RADIC is less than the median of 0.521 kg day⁻¹ per capita in China, and much smaller than in rural areas of developed countries (RADEC). Organic waste and inert waste with an accumulative mass percentage of 72.31% are dominant components of domestic waste in the rural areas of China. There are trends of increasing amounts of kitchen waste, paper/cardboard, and plastic/rubber and a decreasing trend of ash waste. The RADIC composition of domestic waste had a high content of organic waste and a low content of recyclable waste compared to the RADEC. Domestic waste has good compressibility and a light bulk density ranging from 40 to 650 kg m⁻³. The moisture, ash, combustible, and calorific values of domestic waste were 53.31%, 18.03%, 28.67%, and 5368 kJ kg⁻¹, respectively. The domestic waste has an abundance of nutrients including organic matter (39.05%), nitrogen (1.02%), phosphorus (0.50%), and potassium (1.42%). In RADIC, domestic waste can be used as an agricultural manure only after it has been collected and sorted for the potential risk of heavy metal accumulation. Based on these characteristics of domestic waste and the different situations of rural areas, four waste management modes including centralized treatment, decentralized treatment, group treatment, and mobile treatment are designed and discussed.

The aims of this study correspond to (i) determine the feasibility of synthesize geomaterial from two main Pb-contaminated mining sediments (Sed1 and Sed2) without prior activation in substitution to metakaolin (MK), (ii) understand the mechanisms involved toward two types of silicate solution (Na and K one), and (iii) to evaluate the change in the Pb metallic element speciation and leaching after alkali treatment. The raw material as well as consolidated material were characterized by X-ray diffraction, infrared spectroscopy, and electron microscopy. The mechanical properties were evaluated, and the leaching behavior realized according to EN12457-2. The results evidence the limit of mining sediment incorporation by substitution near 50% whatever the sediments and the alkaline solution used. There is no difference in the mechanical properties up to 10% substitution then decrease with the increase of sediment content. The Pb-bearing phases are dissolved during alkaline treatment and redistributed in the geomaterial matrix. Finally, the leaching experiments clearly evidenced the possibility to stabilize Pb into MK-based geomaterial matrix up to 25–30% weight of mine waste.

Composting is considered as one of the main sustainable methods for the treatment of livestock manure. In this study we investigated the effects of additives (urea and rice straw) on methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) emissions using a traditional Chinese pig slurry composting method over an 81-day period, as well as examining total organic carbon and total nitrogen loss. Four common treatment strategies were examined in this study: a control (MC), urea nitrogen addition (MN), composting using rice straw cover (MScₒᵥₑᵣ), and compost mixed with rice straw (MSₘᵢₓ). Our results indicate that the addition of urea resulted in the lowest total CH₄ emissions and the highest N₂O emissions. MScₒᵥₑᵣ treatment had the highest and most significant effect on CH₄ emissions, while MSₘᵢₓ treatment had the lowest CO₂ emissions. Carbon lost through CH₄ and CO₂ released during the experiment was 0.1–0.9 and 2.4–3.9% of total carbon loss, respectively, and nitrogen lost through N₂O release was 11.1–17.9% of total nitrogen. In general, although MSₘᵢₓ, MScₒᵥₑᵣ, and MN treatments increased global warming potential by 21.4, 41.6, and 50.9% per kg of pig slurry, respectively, no statistical differences between the four treatments were recorded. By considering carbon and nitrogen conservation, as well as the improvement of the quality of compost and the mitigation of greenhouse gases (GHGs), the small-scale composting method of pig slurry alone is an acceptable environmentally friendly strategy for use in China.

Mercury is a metal which is potentially toxic for the environment. Many factors control its retention in the soil, such as cation exchange capacity, pH, clay content, organic matter, and redox potential. It is important to know the phytotoxic effects of soil Hg to prevent environmental contamination and its entry into the food chain. Several analytical methods are used to measure metal phytoavailability in soils, but none has been reported for Hg in Oxisols, the most common soil class in Brazil and a very important soil class throughout the tropics. The aim of this study was to select the chemical extractor that best correlated the Hg levels in plants and the Oxisols. The soils used were classified as Dystrophic Red-Yellow Oxisol (LVAd) and Dystroferric Red Oxisol (LVdf), which were collected in the 0–0.2-m soil layer. The species selected for cultivation were a monocotyledon, oat (Avena sativa L. cv. São Carlos) and a eudicotyledon, common bean (Phaseolus vulgaris L. cv. Madrepérola). Each test plot was composed of a 500 cm³ pot filled with soil samples contaminated with HgCl₂. Treatments were arranged in a completely randomized design, with four replications. The experiment was conducted for 30 days. Mercury contents were separately extracted with the following extractors: USEPA 3051A, Mehlich-1, Mehlich-3, DTPA, and water. Mercury was determined by hydride generation atomic absorption spectroscopy. The extracted contents were correlated with the contents in the tissues of the plants’ aerial part by the Pearson correlation. Although it is not considered a standard procedure to evaluate metal phytoavailable contents, the method that presented the best correlations between soil Hg and plant Hg was USEPA 3051A (r = 0.75*). As expected, the worst correlation was with water (r = 0.57* for common bean and r = 0,05ⁿˢ for oat).