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High concentration of arsenic in acid wastewater and polluted river sediment caused by metallurgical industry has presented a great environmental challenge for decades. Nanoscale zero valent iron (nZVI) can detoxify arsenic-bearing wastewater and groundwater, but the low adsorption capacity and rapid passivation restrict its large-scale application. This study proposed a highly efficient arsenic treatment nanotechnology, using the core-shell Fe@Fe 2 O 3 nanobunches (NBZI) for removal of arsenic in acid wastewater with cyclic stability and transformation of arsenic speciation in sediment. The adsorption capacity of As(III) by NBZI was 60 times as high as that of nanoscale zero valent iron (nZVI) at neutral pH. Characterization of the prepared materials after reaction revealed that the contents of As(III) and As(V) were 65% and 35% under aerobic conditions, respectively, which is the evidence of oxidation included in the reaction process apart from adsorption and co-precipitation. The presence of oxygen was proved to improve the adsorption ability of the prepared NBZI towards As(III) with the removal efficiency increasing from 68% to 92%. In order to further enhance the performance of NBZI-2 in the absence of oxygen, a new Fenton-Like system of NBZI/H 2 O 2 to remove arsenic under the anoxic condition was also proposed. Furthermore, the removal efficiency of arsenic in acid wastewater remained to be 78% after 9 times of cycling. Meanwhile, most of the mobile fraction of arsenic in river sediment was transformed into residues after NBZI treatment for 20 days. The reaction mechanism between NBZI and arsenic was discussed in detail at last, indicating great potential of NBZI for the treatment of arsenic in wastewater and sediment. [ABSTRACT FROM AUTHOR]

Low-cost biochar adsorbent owning great potential for environmental remediation faces a bottleneck in application for its unsatisfied adsorption performance. Compared to the efforts on increasing adsorption capacity, improving adsorption speed which is important for treatment efficiency is often neglected. Herein, a hierarchical porous biochar (HPB) derived from shrimp shell was prepared and exhibited good adsorption capacity (Q m >300 mg/g) and fast adsorptive equilibrium (≤10 min) towards three typical aromatic organics, whose adsorption universality was further proved by two-way ANOVA analysis. Whereafter, model analysis demonstrated that, the adsorptive forms (mono- and multi-layers) on HPB depended on whether the contaminant is charged. Compared to the benzene-ring site of organics, the charged site contributed 5.13 times to adsorption promotion in monolayer but -0.49 times in inhibition for multilayers forms. Simultaneously, functional group sites contributed relatively weak (0.023 to 0.342 times only). Following structural control revealed that, hierarchical pore structure of HPB was the key for the fast adsorption speed, and highly graphitic structure was important for the high adsorption capacity. This study aims to provide an advanced biochar adsorbent, not only in adsorption capacity but also in adsorptive speed, and reveal the relationship between the structure and adsorption performance of biochar. [ABSTRACT FROM AUTHOR]

Pollution of Sb(III) in water has caused great concern in recent years. Nanoscale zero-valent iron (nZVI) can detoxify Sb(III) polluted water, but the rapid passivation and low adsorption capacity limit its practical application. Hence, this study provides a new and efficient nanotechnology to remove Sb(III) using the sulfidated nanoscale zero-valent iron (S-nZVI). The S-nZVI exhibits higher Sb(III)-removal efficiency than pristine nZVI under both aerobic and anoxic conditions. The adsorption capacity of Sb(III) by optimized S-nZVI (465.1 mg/g) is 6 times as high as that of the pristine nZVI (83.3 mg/g) under aerobic conditions. The results indicate that Sb(III) and Sb(V) can be immobilized on the surface of S-nZVI by forming Fe-S-Sb precipitates. Moreover, characterization results demonstrate that the existence of S2− can not only activate H 2 O 2 to produce hydroxyl radical, but also accelerate the cycle of Fe3+/Fe2+ to improve the efficiency of Fenton reaction. Therefore, S-nZVI can produce more hydroxyl radicals to oxidize Sb (III) to Sb (V) and results in 2.3-fold higher oxidation rate of Sb(III) compared to pristine nZVI. The formed FeS layer on the S-nZVI surface can also improve the release ability of Fe2+ and accelerate the formation of nZVI corrosion products. S-nZVI thus holds great potential to be applied in antimony removal. Unlabelled Image • The existence of S2− enhanced the oxidation ability of S-nZVI to Sb(III) • The cycle of Fe3+/Fe2+ was accelerated in S-nZVI system • The mechanism of antimony under aerobic or anoxic conditions were investigated [ABSTRACT FROM AUTHOR]

Abstract The adsorbability on the carbonaceous cathode plays an important role in electro-Fenton systems but does not obtain enough attention. In this work, various carbon felts were obtained with different adsorption property by using the method of KOH activation at different temperatures to explore the influence of adsorption on the degradation efficiency of tetracycline (TC). The results of morphology characterization, nitrogen adsorption-desorption tests, XPS and FTIR analysis revealed that the surface area of carbon felt was improved, and the oxygen-containing functional groups on the surface were increased via KOH method with significantly enhanced adsorption capacity. In the batch experiment of TC electro-Fenton degradation, the carbon felt with better adsorption capacity tended to get higher degradation and mineralization efficiency. With the KOH activation process, CF-900 (carbon felt at 900 °C for 1 h) exhibited the best TC adsorption property for the removal of TC within 30 min (initial concentration: 80 mg/L). Meanwhile, the constant of reaction rate for TC degradation at the CF-900 is 0.0648 min−1. It is higher than that (0.012 min−1) obtained at the raw carbon felt (∼5 times of enhancement). There are also synergistic effects between adsorption and degradation performance on some other organic pollutants. In addition, the degradation pathway was also studied by the methods of solid-phase extraction and high performance liquid chromatography-mass spectrometry (HPLC). From the obtained results, it is shown that good adsorbability is favorable for degradation in the homogeneous electro-Fenton system. Graphical abstract Unlabelled Image Highlights • The KOH activation method enhanced the surface chemical adsorption of carbon felt. • The synergistic effect between adsorption and degradation was shown. • Comparison of four different carbon felts in the electro-Fenton process. • The optimal removal capacity was found in the modified carbon felts. • The solid-phase extraction method was used to extract the degradation products. [ABSTRACT FROM AUTHOR]

Abstract Although oxidation of As(III) to As(V) is deemed necessary to promote arsenic removal, the oxidation process usually involves toxic byproducts, well-defined conditions, energy input or sludge generation. Moreover, extra operations are required to remove the resulting As(V). A heterogeneous catalytic process of CuFe 2 O 4 with peroxymonosulfate (PMS) is established for As(III) oxidation and adsorption. The PMS can be activated by CuFe 2 O 4 to generate radical species for As(III) oxidation. The CuFe 2 O 4 /PMS has a stronger affinity for arsenic than CuFe 2 O 4 alone. Oxidation and adsorption promote each other. As a result, the heterogeneous catalytic process is more efficient for As(III) removal than a preoxidation of As(III) followed by adsorption. The adsorption capacity for As on CuFe 2 O 4 /PMS reached up to 63.9 mg/g, which is much higher than that of As(III) (36.9 mg/g) or As(V) (45.4 mg/g) on CuFe 2 O 4 alone. The process can work effectively over a wide range of pH values (3–9) and temperatures (10–40 °C). Coexisting ions such as sulfate, carbonate, silicate and humic acid have an insignificant effect on As(III) removal. The As(III) (1415 μg/L) can be completely oxidized to As(V) and rapidly removed to below 10 μg/L (less than 15 min) using CuFe 2 O 4 (0.2 g/L)/PMS(100 μM). Moreover, the As(III) (50 μg/L) can be completely oxidized and removed within 1 min. The proposed process is easily applicable for the remediation of As(III)-contaminated water under ambient conditions. Graphical abstract Image 1 Highlights • Powerful radical generation on CuFe 2 O 4 induced by PMS. • Enhanced adsorption capacity for As(III) on CuFe 2 O 4 /PMS than CuFe 2 O 4. • Operation across a broad range of geochemical conditions. • Negligible influence of coexisting substances on As(III) removal. • As(III) (1415 μg/L) could be lowered below 10 μg/L within 15 min. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oxidation sites and adsorption sites were rationally positioned. • Integration of CuO and Fe 2 O 3 significantly improved As(III) removal. • As(III) were completely oxidized and adsorbed. • The adsorbent showed a good reusability for arsenic removal. • As(III) spiked natural groundwater could be effectively treated. Abstract Integration of oxidation and adsorption of adsorbents is highly desired to deep remove As(III) in groundwater. In this study, a superparamagnetic Fe 3 O 4 @SiO 2 @Fe 2 O 3 - CuO/TiO 2 (Mag@Fe-Cu/TiO 2) adsorbent was synthesized using step-by-step precipitation process. The TiO 2 nanoparticles were rationally positioned onto the shell of Fe 2 O 3 -CuO for oxidization of As(III). The Fe 2 O 3 -CuO binary oxide significantly improved As(III, V) adsorption compared to individual oxide (Fe 2 O 3 or CuO). The ingenious design of the adsorbent could give full play to oxidation and adsorption functions. As a result, Mag@Fe-Cu/TiO 2 showed much better As(III) removal performance than Mag@Fe-Cu-TiO 2 prepared by co-precipitation. The maximal adsorption capacity of Mag@Fe-Cu(7)/TiO 2 (8.74) for As(III) reached to 17.49 mg/g under UV irradiation. The removal of As(III) in groundwater was tested using Mag@Fe-Cu/TiO 2 adsorbent. Almost all the As(III) were removed under UV irradiation (t = 24 h for C 0 = 1–5 mg/L or 12 h for C 0 = 20–1000 μg/L, adsorbent dose = 1 g/L, pH = 7.0, T = 25 °C). Moreover, it could be easily separated from treated water with an external magnet and well reused maintaining a high As(III) adsorption capacity. Furthermore, the adsorbent could effectively treat arsenic spiked natural groundwater. The adsorption followed the inner-sphere complex mechanism via the chemical interactions between metal (M: Fe and Cu) and arsenic species (As) forming M O As bonds. [ABSTRACT FROM AUTHOR]

The presence of exogenous carbonaceous materials (ECMs) in organic contaminated soil is widespread because of their intentional application as carbonaceous amendments (e.g. biochar and activated carbon) or unintentional discharge (e.g. carbon nanomaterials). Most research so far has focused on the sorption behaviors of ECMs in soil. However, the impact of ECMs on the bioavailability of organic pollutants (OPs) and their ecological damages remain unclear. This paper presents an overview on how the ECMs affect bioavailability of OPs to different organisms, such as microorganisms, plants and earthworms. This is affected by different biological response and properties of ECMs. Moreover, the possible risks of ECMs on soil biota are also discussed at different level. This review presents a unique insight into risk assessment of ECMs. Further researches should focus on possible change in physicochemical characteristics of ECMs when exposed to the natural environment and the consequent influence on their sorption ability and ecotoxicity outcomes. [ABSTRACT FROM AUTHOR]