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Abstract: The aim of this study is to develop a polyethylenimine (PEI) grafted magnetic porous adsorbent for highly effective adsorption of heavy metals. The process of grafting PEI was confirmed by Fourier transform infrared (FTIR) analysis. Batch tests were carried out to investigate the adsorption performance. Adsorption of Cu2+, Zn2+ and Cd2+ was dependent on pH and increasing the pH was favorable to metal ions removal. The adsorption equilibrium was reached within 10min and well described by pseudo-second-order model. The sorption isotherms of the adsorbent for these metals fitted well with Langmuir model, with maximum adsorption capacities of 157.8, 138.8 and 105.2mg/g for Cu2+, Zn2+ and Cd2+, respectively. Competitive adsorption among the three metal ions showed a preferential adsorption of Cu2+ >Zn2+ >Cd2+. The magnetic adsorbent exhibited excellent acid–alkali stability. In addition, the exhausted adsorbent can be regenerated by 0.02mol/L EDTA solution without significant adsorption capacity loss. [Copyright &y& Elsevier]

Municipal sewage sludge (MS)-derived biochar shows low-cost superiority as a potential adsorbent in organic contaminants removal, but limited by its poor adsorption capacity and heavy metal leaking risk. Herein, a novel and effective alkali-acid combined method was proposed for its modification and applied to tetracycline adsorption. The associative facilitation between the alkali and acid modifications was explored, and the influences of pyrolysis temperatures on MS-biochar’s properties were investigated. The successfully preserved γ-Fe 2 O 3 vested SNMS-800 with magnetism. It turned out that SNMS-800 exhibited optimum performance for tetracycline removal with adsorption capacity up to 286.913 mg/g, where all goodness-of-fit indexes of isothermal models were measured by MPSD model. The strong adsorption mechanisms were dominated by two considerable interactions, including strong π-π stacking interaction and pore-filling effect due to the significantly enhanced porosity which was proved by density functional theory model calculations. It manifested that appropriate multiple relation (1.7–6 times) between adsorbent’s pore size and adsorbate size closely related to the adsorption strength. The remarkably improved and stable adsorption capacity, extremely low-cost, easy magnetic preparation, and good reusability in natural water samples entrusted SNMS-800 with good potential for actual aqueous contaminant removal on a large scale. Meanwhile, it provides a clue for materials modification starting with its specific components, and supplies a cost-effective way for municipal sewage sludge’s resource disposal. [ABSTRACT FROM AUTHOR]

A novel adsorbent was prepared by chelating magnetic mesoporous carbon with polyacrylic acid (PAA) to improve the performance of Cd(II) adsorption. Structure characterization demonstrated that the composites were successfully modified with carboxyl groups and preserved ordered mesostructure after modification. The high saturation magnetization (9.2 emu/g) of the modified composites indicated easy and fast separation from water under a moderate magnetic field. Batch experiments with variable pH, contact time and ionic strength were conducted to evaluate the adsorption performance. The modification accelerated the cadmium adsorption rate. The adsorption kinetics of the two materials followed pseudo-second-order model and exhibited 3-stage intraparticle diffusion mode. Equilibrium data were best described by Langmuir model, and the estimated maximum adsorption capacity for the modified adsorbent increased to 406.6 mg/g, which was 140.8% higher than the pristine materials. Moreover, the Cd(II) loaded adsorbent could be regenerated using 0.1 M ethylenediaminetetraacetic acid solution, and the regenerated adsorbent after five cycles could retain 85.2% of the adsorption capacity for the fresh adsorbent. The results suggested that PAA modified adsorbents could be considered to be very effective and promising materials for Cd(II) removal from waste water. [ABSTRACT FROM AUTHOR]

Abstract: A novel magnetically separable laccase immobilized system was constructed by adsorbing laccase into bimodal carbon-based mesoporous magnetic composites (CMMC). A large adsorption capacity (491.7mgg−1), excellent activity recovery (91.0%) and broader pH and temperature profiles than free laccase have been exhibited by the immobilized laccase. Thermal stability was enhanced to a great extent and operational stability was increased to a certain extent. The shift of kinetic parameters indicated affinity change between enzyme and substrate. Application of the immobilized system in phenol and p-chlorophenol removal was investigated in a batch system. Adsorption effects of the support were responsible for the quick removal rate in the first hour, and up to 78% and 84% of phenol and p-chlorophenol were removed in the end of the reaction, respectively, indicating that the magnetic bimodal mesoporous carbon is a promising carrier for both immobilization of laccase and further application in phenol removal. [Copyright &y& Elsevier]

Abstract: An electrochemical DNA sensor for simultaneous detection of functional genes encoding manganese peroxidase (MnP) and cellobiose dehydrogenase (CDH) on a gold electrode was developed. After two thiolated capture probes assembled on the electrode surface, the electrode was exposed to a monolayer of 6-mercapto-1-hexanol (MCH) solution to prevent nonspecific adsorption of target DNA and detection probes. Horseradish peroxidase–streptavidin (HRP–SA) conjugate and laccase–streptavidin (LAC–SA) conjugate were applied for enzyme-amplified amperometric measurement. The two target genes were simultaneously quantified in the same system. The DNA conformation and surface coverage on electrode were characterized by impedance spectroscopy and cyclic voltammetry. The amperometric current responses to HRP and LAC-catalyzed reactions were linearly related to the common logarithm of two target nucleic acids concentrations, ranging from 1×10−11 M to 4×10−8 M and 1×10−10 M to 4×10−8 M. The correlation coefficients were 0.9884 and 0.9881, and the detection limits were 6.2×10−12 M and 3.0×10−11 M, respectively. The effectiveness of this DNA sensor was confirmed by simultaneous detection of two gene fragments extracted from Phanerochaete chrysosporium using polymerase chain reaction (PCR) and restriction endonuclease digestion. The DNA biosensor exhibited good selectivity, precision, stability and reproducibility. [Copyright &y& Elsevier]

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]