Modified clay-based solid-phase phosphorous (P) sorbents are increasingly used as lake geoengineering materials for lake eutrophication control. However, some still dispute the feasibility of using these materials to control internal P loading from shallow eutrophic lakes. The lack of information about P behavior while undergoing frequent sediment resuspension greatly inhibits the modified minerals’ use. In this study, a sediment resuspension generating system was used to simulate the effect of both moderate winds (5.1 m/s) and strong winds (8.7 m/s) on the stability of sediment treated by two geoengineering materials, Phoslock® (a lanthanum modified bentonite) and thermally-treated calcium-rich attapulgite. This study also presents an analysis of the P dynamics across the sediment-water interface of two shallow eutrophic lakes. In addition, the effect of wind velocity on P forms and P supply from the treated sediment were studied using chemical extraction and diffusive gradients in thin films (DGT) technique, respectively. Results showed that adding geoengineering materials can enhance the stability of surface sediment and reduce the erosion depth caused by wind accordingly. All treatments can effectively reduce soluble reactive phosphorus (SRP) concentration in overlying water when sediment is capped with thermally-treated calcium-rich attapulgite, which performs better than sediment mixed with modified attapulgite but not as well as sediment treated with Phoslock®. However, their efficiency decreased with the increase in occurrences of sediment resuspension. The addition of the selected geoengineering materials effectively reduced the P fluxes across sediment-water interface and lowered P supply ability from the treated sediment during sediment resuspension. The reduction of mobile P and enhancement of calcium bound P and residual P fraction in the treated sediment was beneficial to the long-term lake internal P loading management. All of the results indicated that the studied geoengineering materials are suitable for application in shallow eutrophic lakes with frequent sediment resuspension activity.

Offshore oil and gas activities can result in the discharge of large amounts of drilling muds. While these materials have generally been regarded as non-toxic to marine organisms, recent studies have demonstrated negative impacts to suspension feeding organisms. We exposed the arctic-boreal sponge Geodia barretti to the primary particulate components of two water-based drilling muds; barite and bentonite. Sponges were exposed to barite, bentonite and a natural reference sediment at a range of total suspended solid concentrations (TSS = 0, 10, 50 or 100 mg/L) for 12 h after which we measured a suite of biomarker responses (lysosomal membrane stability, lipid peroxidation and glutathione). In addition, we compared biomarker responses, organic energy content and metal accumulation in sponges, which had been continuously or intermittently exposed to suspended barite and natural sediment for 14 d at relevant concentrations (10 and 30 mg TSS/L). Lysosomal membrane stability was reduced in the sponges exposed to barite at 50 and 100 mg TSS/L after just 12 h and at 30 mg TSS/L for both continuous and intermittent exposures over 14 d. Evidence of compromised cellular viability was accompanied by barite analysis revealing concentrations of Cu and Pb well above reference sediments and Norwegian sediment quality guidelines. Metal bioaccumulation in sponge tissues was low and the total organic energy content (determined by the elemental composition of organic tissue) was not affected. Intermittent exposures to barite resulted in less toxicity than continuous exposure to barite. Short term exposures to bentonite did not alter any biomarker responses. This is the first time that these biomarkers have been used to indicate contaminant exposure in an arctic-boreal sponge. Our results illustrate the potential toxicity of barite and the importance of assessments that reflect the ways in which these contaminants are delivered under environmentally realistic conditions.

Cadmium (Cd) is a non-essential trace element that accumulates in agricultural soils through the application of Cd-rich phosphate fertiliser. Vegetables can accumulate Cd to concentrations that sometimes exceed food safety standards. We investigated the potential of low-cost soil amendments to reduce Cd uptake by spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.) and onion (Allium cepa L.). Batch sorption experiments revealed the relative sorption of Cd by biosolids, charcoal, lignite, sawdust, two types of compost, bentonite and zeolite. Lignite and compost had the greatest ability to sorb Cd and were subsequently selected for pot trials, which elucidated their effect on Cd uptake by onions, spinach and lettuce in two market garden soils with native Cd concentrations of 1.45 mg/kg and 0.47 mg/kg. The addition of 2.5% (dry w/w) municipal compost reduced the Cd concentration in onions, spinach and lettuce by up to 60% in both soils. The addition of lignite gave variable results, which depended on the soil type and rate of addition. This Cd immobilisation was offset by soil acidification caused by the lignite. The results indicate that municipal compost is a low-cost soil conditioner that is effective in reducing plant Cd uptake.

With the development and application of graphene oxides (GO), the potential toxicity and environmental behavior of GO has become one of the most forefront environmental problems. Herein, a novel nanoscale layered double hydroxides (glycerinum-modified nanocrystallined Mg/Al layered double hydroxides, LDH-Gl), layered double oxides (calcined LDH-Gl, LDO-Gl) and metallic oxide (TiO2) were synthesized and applied as superior coagulants for the efficient removal of GO from aqueous solutions. Coagulation of GO as a function of coagulant contents, pH, ionic strength, GO contents, temperature and co-existing ions were studied and compared, and the results showed that the maximum coagulation capacities of GO were LDO-Gl (448.3 mg g−1) > TiO2 (365.7 mg g−1) > LDH-Gl (339.1 mg g−1) at pH 5.5, which were significantly higher than those of bentonite, Al2O3, CaCl2 or other natural materials due to their stronger reaction active and interfacial effect. The presence of SO32− and HCO3− inhibited the coagulation of GO on LDH-Gl and LDO-Gl significantly, while other cations (K+, Mg2+, Ca2+, Ni2+, Al3+) or anion (Cl−) had slightly effect on GO coagulation. The interaction mechanism of GO coagulation on LDO-Gl and TiO2 might due to the electrostatic interactions and strong surface complexation, while the main driving force of GO coagulation on LDH-Gl might be attributed to electrostatic interaction and hydrogen bond, which were further evidenced by TEM, SEM, FT-IR and XRD analysis. The results of natural environmental simulation showed that LDO-Gl, TiO2 or other kinds of natural metallic oxides could be superior coagulants for the efficient elimination of GO or other toxic nanomaterials from aqueous solutions in real environmental pollution cleanup.

Acid mine drainage (AMD) is a persisting environmental problem and a grievous nuisance in the mining sector. In this study, iron (Fe(II)) removal was tested in AMD samples collected from the Enugu Okpara abandoned coal mine (Nigeria), having iron concentrations of ∼1300 mg/l. Digestion, toxicity characteristic leaching procedure (TCLP), and batch adsorption tests using coal bottom ash (BA), bentonite clay (BC), and coal fly ash (FA) were performed. Apart from elucidating the effects of adsorbent dose and initial Fe(II) concentrations on the maximum adsorption capacity (q ₑ) of the adsorbents, the experimental data were also fitted to well-known adsorption isotherms and kinetic models. The results from batch tests showed that the optimum adsorbent dosages for BA, BC, and FA were found to be 3, 4, and 4 g per 100 ml, respectively. Among the different adsorption isotherm models tested, the Temkin model fitted the experimental data well for Fe(II) removal. Results from kinetic analysis showed that the Fe(II) removal efficiency increased with an increase in the contact time and then remained almost constant after 30 min for the three tested adsorbents.

The present study examines the efficiency of soil amendments regarding the retention of chromate ions, from water and cultivated soil with wheat (Triticum durum). The minerals and iron oxides that have been used were zeolite, bentonite, goethite, and zeolite modified with goethite I and II. Each adsorbent was added to different Cr solutions, either Cr(NO₃)₃·9H₂O or CrO₃ in a proportion of 1/100 g adsorbent mL⁻¹ solution. Moreover, greenhouse experiments were also conducted using the above materials as soil amendments. Two doses of chromate ions, i.e., 50 mg Cr(III) L⁻¹ in the form of Cr(NO₃)₃·9H₂O and 1 mg Cr(VI) L⁻¹ in the form of CrO₃, were added to plant pots cultivated with wheat. According to the results, the uptake of chromate ions from aqueous solutions onto different adsorbents has shown that modified zeolites (Z-G I and II) adsorb the highest amount of chromate ions, compared to all the other adsorbents. The statistical analysis of the greenhouse experimental data has shown that the increase of the dry weight in soils with amendments follows the order: Z-G II > G > Z-G I > B > Z for pots where Cr(NO₃)₃·9H₂O solutions were added and Z-G II > G > Z > Z-G I > B for pots where CrO₃ solutions were added, respectively. Moreover, all the used soil amendments reduced the total Cr concentration in plants, especially Z-G II. Consequently, such modified zeolites can be used for the remediation of polluted soils with chromium and the production of high-quality food products.

Solidification/stabilization (S/S) of sediments is frequently used to treat contaminants in dredged sediments. In this study, sediment collected from the Pearl River Delta (China) was solidified/stabilized with three different kinds of functional materials: cement, lime and bentonite. Lime primarily acted via induced increases in pH, while cements stabilization occurred through their silicate-based systems and the main function of bentonite was adsorption. The speciation and leaching behaviors of specific heavy metals before and after S/S were analyzed and the results showed that the residual speciation of Cd, Cr, Ni, Pb and Zn increased in all treatments except for Cu, as the exchangeable speciation, carbonate-bound speciation and Fe-Mn-oxide-bound speciation of Cu (all of which could be stabilized) were less than 2 % of the total amount. Pb leaching only decreased when pH increased, while the mobility of Cr and Ni only decreased in response to the silicate-based systems. The leached portion of the Fe-Mn-oxide-bound speciation followed the order Zn > Cu > Ni/Cd > Pb > Cr. The leached portion of organic-matter-bound species was less than 4 % for Cd, Cr, Ni and Pb, but 35.1 % and 20.6 % for Cu and Zn, respectively.

Lanthanum-modified bentonite has potential for wide application in eutrophication control. We investigated P adsorption on a lanthanum-modified bentonite by analysis of adsorption kinetics, equilibrium, and the effect of environmental factors. P adsorption closely followed the pseudo-second-order kinetic model, and the isotherm was well described by the Langmuir model. This adsorbent could effectively immobilize P into the sediment, but the adsorption process was strongly dependent on pH, anions, and low molecular weight organic acids (LMWOAs). P adsorption increased with increasing pH from 0.52 mg P/g at pH 3.0 to 0.93 mg P/g at pH 7.0 with no adsorption at pH 11. P adsorption was strongly inhibited in the presence of anions and three LMWOAs, with P even re-released at high concentrations. These environmental factors should be given significant attention when considering the application of lanthanum-modified bentonite in eutrophication control.

This work investigates influence of different aluminosillicate nanoparticles (NPs) which are found in air in selected workplaces on the properties of the phospholipid (DPPC) monolayer at air–saline interface considered as ex vivo model of the lung surfactant (LS). The measurements were done under physiological-like conditions (deformable liquid interface at 37 °C) for NP concentrations matching the calculated lung doses after exposure in the working environment. Measured surface pressure–area (π–A) isotherms and compressibility curves demonstrated NP-induced changes in the structure and mechanical properties of the lipid monolayer. It was shown that hydrophilic nanomaterials (halloysite and bentonite) induced concentration-dependent impairment of DPPC’s ability of attaining high surface pressures on interfacial compression, suggesting a possibility of reduction of physiological function of natural LS. Hydrophobic montmorillonites affected DPPC monolayer in the opposite way; however, they significantly changed the mechanical properties of the air–liquid interface during compression. The results support the hypothesis of possible reduction or even degradation of the natural function of the lung surfactant induced by particle–phospholipid interactions after inhalation of nanoclays. Presented data do not only supplement the earlier results obtained with another LS model (animal-derived surfactant in oscillating bubble experiments) but also offer an explanation of physicochemical mechanisms responsible for detrimental effects which arise after deposition of inhaled nanomaterials on the surface of the respiratory system.

This paper reports on recycling of industrial wastes (three pharmaceutical industrial sludges) into environmental friendly value-added materials. Stabilization/Solidification (S/S or bricks) process was applied to make a safer way for the utilization of pharmaceutical waste. The additives in this study include binders (cement, lime and bentonite) and strengthening material (pulverized fuel ash (PFA), silica fume and quarry dust) was used at different compositions. Bricks were cured for 28 days, and the following analysis-like compressive strength, leachability of heavy metals, mineralogical phase identity by X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and thermal behaviour by thermogravimetric-differential thermal analysis (TG-DTA) had done. All the bricks were observed to achieve the standard compressive strength as required for construction according to BIS standards. Metal concentration in the leachate has reached the dischargeable limits according to Brazilian standards. Results of this study demonstrate that production of bricks is a promising and achievable productive use of pharmaceutical sludge.