In this study natural bentonite (NB) and acid-thermal co-modified bentonite (MB) were utilized as adsorbents for the removal of Thymol Blue (TB) from aqueous solution. The batch adsorption experiments were conducted under different experimental conditions. The artificial neural network (ANN) and adaptive neuro fuzzy inference systems (ANFIS) were applied to estimate removal percentage (%) of TB. Mean squared error (MSE), root mean square error (RMSE) and coefficient of determination (R2) values were used to evaluate the results. In addition, the experimental data were fitted isotherm models (Langmuir, Freundlich and Temkin) and kinetic models (pseudo first order (PFO), pseudo second order (PSO) and intra-particle diffusion (IPD)). The adsorption of TB on both the NB and MB followed well the PSO kinetic model, and was best suited Langmuir isotherm model. When the temperature was increased from 298 K to 323 K for 20 mg/L of TB initial concentration, the removal percentage of TB onto the NB and MB increased from 74.91% to 84.07% and 81.19% to 93.12%, respectively. This results were confirmed by the positive ΔH° values indicated that the removal process was endothermic for both the NB and MB. The maximum adsorption capacity was found as 48.7805 mg/g and 117.6471 mg/g for the NB and MB, respectively (at 323 K). As a result, with high surface area and adsorption capacity, the MB is a great candidate for TB dye removal from wastewater, and the ANFIS model is better than the ANN model at estimating the removal percentage of the dye.

cadmium usually enter the environment and water resources through wastewater, released by various industries, and may have adverse effects. The current study employs surface of bentonite clay available locally in order to remove cadmium In solutions contaminated with this type of ions, in order to research on a surface with a high ability to adsorption of cadmium (II) ions, study Some factors affect the adsorption process on bentonite clay, such as contact time, pH the solution, Adsorbent particle size, Initial concentration of solutions and temperature of the solution were examined in the a batch process mode. The amount of adsorbed Cd (II) increased with height temperature, the optimum adsorption pH was about 6.5. Under this condition, the percent removal was 95.17%. The adsorption  isotherms were studied and  the results of adsorption processes were more fitted with Friendlich model rather than Langmuir adsorption model. Thermodynamic study showed that,  ΔH was endothermic, ΔG is found to be negative That is, the process is automatic and  ΔS was found to be positive. The current study also involves  practical application using bentonite to get rid of Cd(II) ions  to  from wastewater of Hamdan's station of the Basra- iraq, The results indicate high affinity (97.84%) removal of Cd(II) ions.

Establishment of submerged macrophyte beds and application of chemical phosphorus inactivation are common lake restoration methods for reducing internal phosphorus loading. The two methods operate via different mechanisms and may potentially supplement each other, especially when internal phosphorous loading is continuously high. However, their combined effects have so far not been elucidated. Here, we investigated the combined impact of the submerged macrophyte Vallisneria denseserrulata and a lanthanum-modified bentonite (Phoslock®) on water quality in a 12-week mesocosm experiment. The combined treatment led to stronger improvement of water quality and a more pronounced reduction of porewater soluble reactive phosphorus than each of the two measures. In the combined treatment, total porewater soluble reactive phosphorus in the top 10 cm sediment layers decreased by 78% compared with the control group without Phoslock® and submerged macrophytes. Besides, in the upper 0–1 cm sediment layer, mobile phosphorus was transformed into recalcitrant forms (e.g. the proportion of HCl–P increased to 64%), while in the deeper layers, (hydr)oxides-bound phosphorus species increased 17–28%. Phoslock®, however, reduced the clonal growth of V. denseserrulata by 35% of biomass (dry weight) and 27% of plant density. Our study indicated that Phoslock® and submerged macrophytes may complement each other in the early stage of lake restoration following external nutrient loading reduction in eutrophic lakes, potentially accelerating the restoration process, especially in those lakes where the internal phosphorus loading is high.

Powder adsorbents show an excellent adsorption capacity for arsenic(As) due to the large specific surface area. However, the performance of powder adsorbents decreases significantly by channeling in the adsorption bed, and the powder is released from the bed. Pelletization of power adsorbent can solve the problems, and bentonite was proposed as a binder to improve the strength. The adsorption capacity and lifetime of pelletized adsorbent were evaluated through a batch and column study. The addition of bentonite decreased adsorption capacity by 16% of pellet without bentonite, but improved compressive strength of adsorbent up to 3.6 times. In the batch test, the maximum adsorption capacity of pelletized adsorbent is 22.2 mg As/g, which is about 40% of powder adsorbent. However, in the column study, pellet adsorbent showed similar adsorption performance and lifetime to commercial and powder adsorbent. As a result, the pellet adsorbent using bentonite is a potential low-cost adsorbent to remove effectively As in the aqueous phase.

Multi-layered engineered landfill consists of the bottom liner layer (mainly bentonite clay (B)) upon which the hazardous wastes are dumped. In current practice, sand (S) is mixed with bentonite to mitigate the adverse effects of using bentonite alone in the liner layer. Incorporation of waste and unutilized fly ash (FA) as an amendment material to B has been explored in terms of its hydro-mechanical properties, but not gauged its adsorption potential. Indian subcontinent primarily relies on the thermal power source, and FA dumps have already reached its full capacity. The objective of this study is to explore the adsorption characteristics of four B-FA composite mixes sourced within India, considering Pb²⁺ as a model contaminant. The effect of fly ash type, fly ash amendment rate and adsorbate concentration was explored in the current study and juxtaposed with B-S mixes, based on 960 batch adsorption tests. Both B-FA and B-S mixes reached equilibrium adsorption capacity within 65 min. At higher adsorbate concentrations (commonly observed in the liner), B-FA mixes exhibited superior adsorption capacity, mainly one mixed with Neyvelli fly ash (NFA). The effect of higher amendment rate had little impact on the adsorption capacity at different concentration, but gradually decreased the percentage removal of Pb²⁺. The B-S mix showed a drastic decrease in percentage removal at higher adsorbate concentration among all tested mixes. Systematic characterization including geotechnical properties, microstructure and chemical analysis was also done to interpret the obtained results. Both Freundlich and Langmuir models fitted the isotherm data well for all B-FA mixes. The maximum adsorption capacity from the isotherm was correlated to easily measurable Atterberg limits by two empirical relationships.

Clay minerals are the most popular adsorbents/amendments for immobilizing heavy metals in contaminated soils, but the dissolved organic matter (DOM) in soil environment would potentially affect the adsorption/immobilization capacity of clay minerals for heavy metals. In this study, the effects of DOM derived from chicken manure (CM) on the adsorption of cadmium (Cd2+) on two clay minerals, bentonite and zeolite, were investigated. The equilibrium data for Cd2+ sorption in the absence or presence of CM-DOM could be well-fitted to the Langmuir equation (R2 > 0.97). The presence of CM-DOM in the aqueous solution was found to greatly reduce the adsorption capacity of both minerals for Cd2+, in particular zeolite, and the percentage decreases for Cd2+ sorption increased with increasing concentrations of Cd2+ as well as CM-DOM in aqueous solutions. The adsorption of CM-DOM on zeolite was greater than that on bentonite in the absence of Cd2+, however, a sharp increase was observed for CM-DOM sorption on bentonite with increasing Cd2+ concentrations but little change for that on zeolite, which can be attributed to the different ternary structures on mineral surface. The CM-DOM modified clay minerals were utilized to investigate the effect of mineral-adsorbed CM-DOM on Cd2+ sorption. The adsorbed form was found to inhibit Cd2+ sorption, and further calculation suggested it primarily responsible for the overall decrease in Cd2+ sorption on clay minerals in the presence of CM-DOM in aqueous solutions. An investigation for the mineral surface morphology suggested that the mineral-adsorbed CM-DOM decreased Cd2+ sorption on bentonite mainly through barrier effect, while in the case of zeolite, it was the combination of active sites occupation and barrier effect. These results can serve as a guide for evaluating the performance of clay minerals in immobilizing heavy metals when animal manure is present in contaminated soils.

Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm–10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1–1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18–25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems.

The fractionation and speciation of As in a contaminated soil were investigated, and a remediation strategy was tested. Regarding speciation, we found that As(V) prevails over As(III) whereas more than 40% of total arsenic is in organic form. The fractionation of As was investigated with two sequential extraction methods: a low mobility was found. Then we tested the possibility of using phosphoric acid to extract As from the soil and cleaning the washing effluents by sorption onto montmorillonite. The efficiency of the extraction and of the adsorption onto the clay were also investigated for Cr, Cu, Fe, Mn, Ni, Pb and Zn, whose total concentrations and fractionation in the soil are reported here. The extraction percentages for As and metals ranged from 30 to 65%; the residual proportions in the soil are presumably in very unreactive forms. Montmorillonite showed a good uptake capacity towards the investigated pollutants. Arsenic in a contaminated soil was present in different forms and it was extracted by soil washing followed by effluent treatment by sorption onto a natural clay.

Natural colloids such as clays and natural organic matter (NOM) are universally present in environments, which could interact with microplastics (MPs) and thus alter the fate and transport of MPs in porous media. The co-effects of clays and NOM on MPs transport in saturated porous media were systematically explored at both low and high ionic strength (IS) conditions. Specifically, bentonite and humic acid (HA) were employed as representative clays and NOM. 5 mM NaCl and 1 mM CaCl₂ solutions were used as low IS conditions, while 25 mM NaCl and 5 mM CaCl₂ solutions were employed as high IS conditions. We found that formation of MPs-bentonite heteroaggregates had great effects on MPs transport under different conditions. Without HA, the small MPs-bentonite heteroaggregates formed under low IS increased MPs transport via serving as mobile carriers, while larger MPs-bentonite heteroaggregates formed at high IS led to the decreased MPs mobility. When both HA and bentonite were copresent in MPs suspension, we found that HA could inhibit the formation of larger sized MPs-bentonite heteroaggregates. Particularly, when the two types of natural colloids copresent in MPs suspensions, MPs transport behaviors were similar to those with only bentonite present in MPs suspensions at low IS, while MPs transport was greatly increased at high IS comparing with those only with bentonite in suspensions. Clearly, without HA in suspensions, bentonite played the dominant role on MPs transport under all examined conditions concerned in this study. Instead, when both HA and bentonite copresent in MPs suspensions, MPs transport was mainly controlled by bentonite at low IS, while both bentonite and HA had major contributions at high IS. The results showed that under solution conditions concerned in present study, MPs mobility in porous media would be greatly affected (either enhanced or inhibited) by the two types of natural colloids.

The non-magnetic capping materials are difficult to be recycled from the water bodies after their application, leading to the increase in the cost of the sediment remediation. To address this issue, a capping material, i.e., magnetic lanthanum/iron-modified bentonite (M-LaFeBT) was prepared by loading lanthanum onto a magnetic iron-modified bentonite (M-FeBT) and used to control the internal phosphorus (P) loading in this study. To determine the capping efficiency and mechanism of M-LaFeBT, the impact of M-LaFeBT and M-FeBT capping on the mobilization of P in sediments was investigated, and the stabilization of P bound by the M-LaFeBT and M-FeBT capping layers was evaluated. Results showed that M-LaFeBT possessed good magnetic property with a saturated magnetization of 14.9 emu/g, and exhibited good phosphate adsorption ability with a maximum monolayer sorption capacity (QMAX) of 14.3 mg P/g at pH 7. Moreover, M-LaFeBT capping tremendously reduced the concentration of soluble reactive P (SR-P) in the overlying water (OL-water), and the reduction efficiencies were 94.7%–97.4%. Furthermore, M-LaFeBT capping significantly decreased the concentration of SR-P in the pore water and DGT (diffusive gradient in thin films)-labile P in the profile of OL-water and sediment. Additionally, most of P bound by the M-LaFeBT capping layer (approximately 77%) was stable under natural pH and reducing conditions. The phosphate adsorption ability for M-LaFeBT was much higher than that for M-FeBT, and the QMAX value for the former was 4.86 times higher than that for the latter. M-LaFeBT capping gave rise to a higher reduction of DGT-labile concentration in the profile of OL-water and sediment than M-FeBT capping. The P adsorbed by the M-LaFeBT capping layer was more stable than that by the M-FeBT capping layer. Results of this study demonstrate that M-LaFeBT is promising for utilization as an active capping material to intercept sedimentary P release into OL-water.