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Excess nitrogen in stormwater degrades surface water quality via eutrophication and related processes. Bioretention has been recognized as a highly effective low-impact development (LID) technology for the management of high runoff volumes and reduction of nitrogen (N) pollutants through various mechanisms. This paper provides a comprehensive and critical review of recent developments on the biological N removal processes occurring in bioretention systems. The key plant- and microbe-mediated N transformation processes include assimilation (N uptake by plants and microbes), nitrification, denitrification, and anammox (anaerobic ammonia oxidation), but denitrification is the major pathway of permanent N removal. Overall, both laboratory- and field-scale bioretention systems have demonstrated promising N removal performance (TN: >70%). The phyla Bacteroidetes and Proteobacteria are the most abundant microbial communities found to be enriched in biofilter media. Furthermore, the denitrifying communities contain several functional genes (e.g., nirK/nirS, and nosZ), and their concentrations increase near the surface of media depth. The N removal effectiveness of bioretention systems is largely impacted by the hydraulics and environmental factors. When a bioretention system operates at: low hydraulic/N loading rate, containing a saturation zone, vegetated with native plants, having deeper and multilayer biofilter media with warm climate temperature and wet storm events periods, the N removal efficiency can be high. This review highlights shortcomings and current knowledge gaps in the area of total nitrogen removal using bioretention systems, as well as identifies future research directions on this topic.

Biochar is a carbonaceous material that is rich in both carbon and mineral ingredients. Previous research has recognized that properties and various applications of biochar are often correlated wit...

The current investigation focus on the use of brown alga Turbinaria conoides (TC) and polysulfone immobilized Turbinaria conoides (PITC) for the biosorption of rare earth element Thulium (Tm(III)) from aqueous systems. To attain the highest removal of Tm(III), the process parameters including the equilibrium pH, Tm(III) concentration and biosorption time were optimized. The characterization techniques were used to analyse the morphological features and elemental analysis of the biosorbents. The isotherm models of selective two and three parameters were subjected to inspect the equilibrium data. The biosorption data fitted to the different biosorption kinetic models. Results illustrated that both TC and PITC displayed higher biosorption capacity of 200.5 and 157.9 mg/g, respectively. Through kinetic trials, we identified delay in equilibrium attainment for PITC and the data were described with intraparticle diffusion model. TC and PITC presented comparable results with biosorption equilibrium attained in 200 min, optimum equilibrium solution pH 5.0 and exhibited maximum biosorption capacity for the initial Tm(III) concentrations of 500 mg/L. Recovery studies represented that the maximum desorption efficiency attained using 0.01 M HCl and PITC presented potential uptake capacity of Tm(III) during the entire 10 biosorption–desorption cycles.

Biochar is a stable carbon-rich product synthesized from biological materials through different heating techniques. The main aim of this review is to evaluate various biochar production methods, pa...

Bioretention is a popular stormwater management strategy that is often utilized in urban environments to combat water quality and hydrological impacts of stormwater. This goal is achieved by selective designing of a system, which consists of suitable vegetation at the top planted on an engineered media with drainage system and possible underdrain at the bottom. Bibliometric analysis on bioretention studies indicates that most of the original research contributions are derived from a few countries and selected research groups. Hence, most of the bioretention systems installed in diverse geographical locations are based on guidelines from climatically different countries, which often lead to operational failures. The current review critically analyzes recent research findings from the bioretention literature, provides the authors’ perspectives on the current state of knowledge, highlights the key knowledge gaps in bioretention research, and points out future research directions to make further advances in the field. Specifically, the role and desired features of bioretention components, the importance of fundamental investigations in laboratory, field-based studies and modeling efforts, the real-time process control of bioretention cells, bioretention system design considerations, and life cycle assessment of full-scale bioretention systems are discussed. The importance of local conditions in guiding bioretention designs in difference climates is emphasized. At the end of the review, current technical challenges are identified and recommendations to overcome them are provided. This comprehensive review not only offers fundamental insights into bioretention technology, but also provides novel ideas to combat issues related to urban runoff and achieve sustainable stormwater management.

Biochar has been increasingly used as a filter medium in engineered low impact development systems (e.g., bioretention systems) for decontamination of urban stormwater and management of hydrology. This review paper critically analyzes the performance of biochar-based biofiltration systems for removal of chemical and microbial pollutants present in urban runoff. Biochar-amended biofiltration systems efficiently remove diverse pollutants such as total nitrogen (32 - 61%), total phosphorus: (45 - 94%), heavy metals (27 - 100%), organics (54 - 100%) and microbial pollutants (log10 removal: 0.78 - 4.23) from urban runoff. The variation of biofiltration performance is due to changes in biochar characteristics, the abundance of dissolved organic matter and/or stormwater chemistry. The dominant mechanisms responsible for removal of chemical pollutants are sorption, ion exchange and/or biotransformation, whereas filtration/straining is the major mechanism for bacteria removal. The pseudo-second order and Langmuir isotherm are the best models that describe the kinetics and chemical equilibrium of pollutants, respectively. This critical review provides the fundamental scientific knowledge for designing highly efficient biochar-based bioretention systems for removal of diverse pollutants from urban stormwater. The key knowledge gaps that should be addressed in future research include long-term field-scale bioretention study, development of novel methods for filter media regeneration/reuse, and dynamics of filter media microbial communities.

It is necessary to explore alternative resources for phosphorus (P) in an effort to address the lack of available P source for crops in an agricultural sector. In this study, bacterial biomass waste of Escherichia coli from a fermentation industry was converted to “P-enriched biochar”, and its possibility as a P fertilizer was assessed. Biochar yields (5.2 ± 0.74% to 19.7 ± 1.54%) highly depended on pyrolysis conditions such as initial weight of feedstock and residence time. Inorganic elemental analysis revealed that the biochar did not consist of any elements with high toxic concentration levels regardless of its yield and that it was rich in P. Biochar with lower yield showed higher water soluble P. Subsequently, a rapid P-release in water and citric acid was initially observed, and a gradual decline one day later was followed. The extractable P in water and citric acid reached 52% and 61%, respectively, of initial P content (84.7 mg g−1) in the biochar in five days. Scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) results showed that P was evenly distributed in macropore-sized biochar matrix, and the contents of P and O decreased after P release into water. Fourier transform infrared spectroscopy (FT-IR) revealed that the peaks related to phosphate form significantly decreased after P release. SEM-EDS and FT-IR results indicated that released form of P was phosphate. Hydroculture bioassay showed that biochar had a positive effect on the early growth of Lactuca sativa. This study suggested that conversion of bacterial waste to the P-enriched biochar could be a feasible strategy for recycling P source as a P fertilizer as well as valorization of wastes from fermentation industry.

Light-induced demineralization of organic pollutants is a recent development in the field of waste treatment. The present study focuses on TiO2-rGO-Ag hybrid nanocomposite through a two-step simultaneous synthesis pathway. The methods primarily involving facile solvothermal treatment (TiO2-rGO nanocomposite) in a water-ethanol mixture, followed by microwave irradiation method for deposition of silver (Ag) nanoparticles over the Binary nanocomposite synthesized. The resulting hybrid photocatalyst was well, and in-detail characterized using analytical techniques such as High-Resolution X-ray Diffractometer (HR-XRD), Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy (TEM/HR-TEM), High-Resolution Scanning Electron Microscopy (HR-SEM), Fourier-Transform Infra-Red Spectroscopy (FT-IR), Energy Dispersive X-Ray Spectroscopy (EDX), Raman Spectroscopy, Solid-State UV–Vis Spectroscopy and X-Ray Photoelectron spectroscopy (XPS). The nanomaterial was examined to determine photocatalytic property by conducting a photodegradation experiment of an aqueous solution of Methylene Blue (MB) dye and monitoring the changes. The photocatalytic efficiency of the nano-hybrid synthesized was also analyzed in detail for the degradation of compounds that active components of petrochemical pollutants such as Benzene, Toluene, and Phenol the Visible region of radiation in a photochemical reactor under ambient reaction conditions. The set of experiments suggested that the photocatalytic efficiency of ternary nanocomposite synthesized was quite noticeable. The variation in the catalyst's photoactivity with the change in the functional group was monitored, and the rate of reaction has been correlated with attached substituents.

Nanoparticles exhibit unique properties that enable them to find potential applications in various fields. Accordingly, significant research attention is being given to the development of novel strategies for the synthesis of nanoparticles. Among these, biological route of nanoparticle synthesis has been portrayed as an efficient, low-cost and environmental friendly technique. Biological materials such as bacteria, fungi, yeast, algae and plant have been reported to possess high bioreduction ability to synthesize various size and shape of metallic nanoparticles. Of these biomaterials, this review focuses on plant-mediated biosynthesis of metallic nanoparticles. The biomolecules present in the plants such as terpenoids, flavones, ketones, aldehydes, proteins, amino acids, vitamins, alkaloids, tannins, phenolics, saponins, and polysaccharides play a vital role in reduction of metals. A systematic comparison of literature, based on the bioreduction capacity of various plant biomass/extract towards various metals under different experimental conditions, is also provided. Various instrumental techniques utilized to characterize nanoparticles are also discussed. Finally, this review also highlights the application of biosynthesized nanoparticles in different fields such as medicine, agriculture, catalytic, cosmetic and food. Thus, this article reviews the achievements and current status of plant-mediated biosynthesis, and hopes to provide insights into this exciting research frontier.

In the present research, a brown marine macroalga ( Turbinaria conoides ) was employed as a novel biosorbent for the sequestration of samarium ions from aqueous solutions. The influence of solution pH, initial Sm(III) concentration and contact time on Sm(III) removal were investigated. The biosorbent was characterized through Fourier transform infrared spectroscopy, potentiometric titration, scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis. Equilibrium experimental results were fitted to isotherm models such as the Langmuir, Freundlich and Redlich–Peterson to obtain the characteristic parameters of each model. The pseudo-first-order and pseudo-second-order kinetic models were used to analyze the experimental kinetic data. The Langmuir and Redlich–Peterson isotherms were found to best fit the equilibrium data and the biosorption kinetics followed the pseudo-second-order model. From the Langmuir isotherm model, the maximum biosorption capacity was found to be 151.6 mg/g at the solution pH 4.0. Desorption experiments revealed that 0.1 M HCl was efficient with good recovery of Sm(III) ions with desorption efficiency of 99.2%.

Finding appropriate rooftop vegetation may improve the quality of runoff from green roofs. Portulaca grandiflora was examined as possible vegetation for green roofs. Green roof substrate was found to have low bulk density (360.7 kg/m3) and high water-holding capacity (49.4%), air-filled porosity (21.1%), and hydraulic conductivity (5270 mm/hour). The optimal substrate also supported the growth of P. grandiflora with biomass multiplication of 450.3% and relative growth rate of 0.038. Phytoextraction potential of P. grandiflora was evaluated using metal-spiked green roof substrate as a function of time and spiked substrate metal concentration. It was identified that P. grandiflora accumulated all metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, and Zn) from metal-spiked green roof substrate. At the end of 40 days, P. grandiflora accumulated 811 ± 26.7, 87.2 ± 3.59, 416 ± 15.8, 459 ± 15.6, 746 ± 20.9, 357 ± 18.5, 565 ± 6.8, and 596 ± 24.4 mg/kg of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn, respectively. Results also indi...

Growth substrate plays an important role in determining the quality of runoff from green roofs. However, no systematic research has been conducted to design a substrate to improve runoff quality. Hence, the present study aimed at designing and developing a green roof substrate using low-cost and environmentally-benign materials. The inorganic fraction of the substrate includes purosil, vermiculite, sand and light-weight clay aggregates (LECA); whereas the organic fraction includes coco-peat and Sargassum wightii. Through factorial design, 13 different substrate mixes were prepared and the optimum mix (20% purosil, 30% vermiculite, 10% sand, 20% LECA, 10% coco-peat and 10% S. wightii) was found to have high water holding capacity (67.6%), air filled porosity (21%), hydraulic conductivity (5524 mm/h) and low bulk density (495 kg/m3). The substrate also provided maximum support for the growth of Portulaca oleracea. Experiments with metal-contaminated influent from the down-flow of a packed reactor re...

The potential of using coco-peat biomass (CPB) has been assessed for the removal of Pb(II), Cd(II), Cu(II) and Ni(II) ions from single and quaternary solutions. According to Langmuir isotherm, the maximum biosorption capacity of CPB was 0.484, 0.151, 0.383 and 0.181 mmol/g for Pb(II), Cd(II), Cu(II) and Ni(II) ions, respectively. Scanning electron microscopy along with energy-dispersive X-ray spectroscopy and Fourier-transform IR spectroscopy confirmed changes in the biosorbent functionality after metal sorption. Through quaternary isotherm experiments, 16.1%, 48.2%, 32.3% and 46.5% decrease in experimental uptakes were observed for Pb(II), Cd(II), Cu(II) and Ni(II), respectively, in the presence of other metal ions.

Fixed-bed column studies were conducted to evaluate the potential of co-immobilized (activated carbon and Bacillus subtilis) (CI) beads for the removal of Cr(VI) from aqueous solution. The impact of various parameters such as initial Cr(VI) concentrations (100, 150, and 200 mg/L), flow rate (3, 9, and 15 mL/min), and bed depth (10, 15, and 20 cm) on Cr(VI) adsorption onto CI beads were investigated. The breakthrough time increased with a decrease in initial Cr(VI) concentration and flow rate, and an increase in bed height. The breakthrough data obtained for Cr(VI) removal was more adequately described by the Thomas model with high correlation coefficients (R 2 = 0.982). The eluent, 0.1 M NaOH, provided high elution efficiencies (~90 %) in all the six cycles. Obtained results pointed out that CI beads could potentially be used for the removal of Cr(VI) from aqueous solution.

Green roofs have been proposed as an efficient and practical tool to combat urbanisation in many countries. This review paper focuses on various benefits associated with green roofs and research efforts made till date to promote green roofs. Through systematic comparison of literature, this review also emphasises knowledge gap that prevail in green roof technology and highlight the need for local research to install green roofs in developing and under-developed countries. Considering that growth substrate, vegetation and drainage layer determine the success of green roof, efforts were made to consolidate desirable characteristics for each of these components and suggests methodology to construct practical green roofs. This critical review also explores limitations associated with green roofs and recommend strategies to overcome. Apart from stand-alone green roofs, there is a huge scope for hybrid green roof systems with other established techniques, which are presented and discussed. Recommendations for future study are also provided.

The water hyacinth plants are renewable natural biomass, proliferate ubiquitously, and abundant in water bodies often posing environmental nuisances. To overcome this problem, a novel approach that utilizes water hyacinth plant has to be arrived. This research work mainly deals with application of low cost, non-conventional, newly developed novel biomaterial, Effective Microorganisms (EM) based Water Hyacinth Compost as biosorbent for the removal of basic dyes from aqueous solution. Biosorption of basic dyes like Methylene Blue (MB), Malachite Green (MG), and Basic Blue 41 (BB41) was investigated using a biosorbent of EM based Water Hyacinth Compost. The biosorbent material was analyzed for physico-chemical composition such as pH, moisture content, organic carbon, nitrogen, etc. and also the biosorbent was characterized before and after adsorption using FTIR and SEM. The batch study was performed to optimize the operational parameters such as pH, biosorbent dosage, biosorbent particle size, and in...

Green roof substrates are usually designed to achieve desirable characteristics such as low bulk density, preparation cost, high water holding capacity (WHC), hydraulic conductivity (HC) and airfilled porosity (AFP). However, no importance is given to sorption capacity or leaching potential of substrate. Thus, in the present study, novel attempt was made to incorporate a brown-seaweed ( Turbinaria conoides ) in growth substrate to enhance the runoff quality from green roofs. The green roof substrate, prepared using 30% perlite, 20% vermiculite, 10% sand, 20% crushed brick, 10% cocopeat and 10% T. conoides , was found to have favourable characteristics such as low bulk density (477.7 kg/m 3 ), high WHC (49.5%), AFP (20.5%) and HC (4210 mm/h). With the aid of down-flow fixed column, sorption capacity of green roof substrate towards various metal ions (Na, K, Ca, Mg, Al, Fe, Cd, Cu, Cr, Ni, Pb and Zn) was examined and results indicated that the column was able to operate for 1440 min at a flow rate of 5 mL/min before outlet Ni concentration reached the inlet. Green roof experiments were performed using pilot-scale assemblies with Portulaca grandiflora as vegetation. Under rainfall simulations, it was observed that vegetated-green roof assemblies acted as a sink for various metal ions and produced better runoff. In addition, green roofs buffered acidic rain and delayed runoff generation.

The aim of the present investigation was to study the potential of two brown seaweeds ( Sargassum wightii and Turbinaria conoides ) to remove praseodymium ions from solutions. Due to swelling problems, the seaweed biomasses were also immobilized using polysulfone matrices which amplified hydraulic conductivity more than 7.1 times. At optimum pH of 5, maximum Pr(III) uptakes of 131.4, 146.4, 111.2 and 119.5 mg/g were observed for free- S. wightii , free- T. conoides , polysulfone immobilized S. wightii (PISW) and polysulfone immobilized T. conoides (PITC), respectively. Experimental biosorption isotherms were successfully described using the Langmuir, Freundlich and Sips model. Owing to intraparticle diffusion, rate of Pr(III) sorption by immobilized biosorbents was slow and equilibrium attainment took 240 min compared to only 90 min by free biomasses. However, regeneration of seaweed biomasses for repeated sorption application was only possible with immobilization biosorbents. With 0.1 mol/L HCl as elutant, both PITC and PISW exhibited invariable Pr(III) uptake capacity and very high mechanical stability over 10 sorption-desorption cycles.

The purpose of this research was to investigate the efficiency of Dracaena marginata planted biofilters to decontaminate urban runoff. A new biofilter growth substrate was prepared using low-cost and locally available materials such as red soil, fine sand, perlite, vermiculite, coco-peat and Sargassum biomass. The performance of biofilter substrate was compared with local garden soil based on physical and water quality parameters. Preliminary analyses indicated that biofilter substrate exhibited desirable characteristics such as low bulk density (1140 kg/m(3)), high water holding capacity (59.6%), air-filled porosity (7.82%) and hydraulic conductivity (965 mm/h). Four different biofilter assemblies, with vegetated and non-vegetated systems, were examined for several artificial rain events (un-spiked and metal-spiked). Results from un-spiked artificial rain events suggested that concentrations of most of the chemical components in effluent were highest at the beginning of rain events and thereafter subsided during the subsequent rain events. Biofilter growth substrate showed superior potential over garden soil to retain metal ions such as Al, Fe, Cu, Cr, Ni, Zn, Cd and Pb during metal-spiked rain events. Significant differences were also observed between non-vegetated and vegetated biofilter assemblies in runoff quality, with the latter producing better results.

For the past few decades, biosorption has been widely investigated for the removal of different contaminants in aqueous media. A number of biomasses of different genre have been identified to possess good biosorption capacity. Insights into biosorption mechanisms have been provided by various researchers in order to develop a fundamental scientific understanding of the biosorption process. However, biosorption has not been employed widely for its large-scale commercial applications. The key factors that affect the growth and evolution of biosorption as a practical technology for decontamination of wastewaters include, (1) lack of investigations on multi-component solutions and wastewaters with complex matrix effects, (2) incomplete understanding of physico-chemical characteristics of biomasses of different types, (3) lack of studies to improve the performance of biosorbents through surface functionalization, and (4) non-integration of biosorption in wastewater/water treatment plants. This critical review aims to identify and discuss the practical limitations of biosorption and provide future research directions to make biosorption a technologically viable process with emphasis on selection and modification of biomasses to suit desired treatment applications, identify appropriate operation modes for large-scale applications of biosorption, and perform techno-economic evaluation of overall biosorption processes.

The discarded materials from different sources can be utilized as effective materials in wastewater remediation. This proposed study was aimed mainly to investigate the possibility of Effective Microorganisms based compost (EMKC), which is derived from the kitchen solid waste, as a non-conventional low cost adsorbent for the removal of malachite green from aqueous solution. Batch experiments were carried out to evaluate the optimum operating parameters like pH (2-9), initial dye concentration (50-1000mg/L), adsorbent particle size (0.6-2.36mm) and adsorbent dosage (2-12g/L). EMKC recorded maximum uptake of 136.6mg/g of MG at pH 8, initial dye concentration 1000mg/L, adsorbent particle size 1.18mm and adsorbent dosage 4g/L. Two and three parameter adsorption models were employed to describe experimental biosorption isotherm data. The results revealed that the Sips model resulted in better fit than other models. The pseudo-first and -second order models were applied to describe kinetic data, of which the pseudo-second order described experimental data better with high correlation coefficient. This investigation suggested that EMKC could be an effective and low cost material for the removal of malachite green dye from aqueous solution. � 2015 Elsevier Inc.

In this study, single and competitive sorption of Pb(II), Cd(II), Cu(II), and Ni(II) ions onto vermiculite were studied. Preliminary examination revealed that vermiculite possesses low bulk density (279kg/m3), a high cation exchange capacity (41.3meq/100g), water holding capacity (62.5%), and air-filled porosity (5.8%). The pH edge experiments indicated that the uptake capacity of vermiculite improved with enhancement in pH and highest value was detected at pH 5. Fourier transform IR spectroscopy along with scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed changes in the sorbent functionality after metal sorption, and the results were in agreement with metal removal studies. It was observed by isotherm experiments that vermiculite was capable of sorbing 0.238, 0.099, 0.199 and 0.115mmol/g of Pb(II), Cd(II), Cu(II) and Ni(II), respectively, according to the Langmuir model. The reaction was rapid and the kinetic experimental data were successfully modelled using the pseudo-first order model. Quaternary biosorption experimental results revealed that severe competition exists between metal ions during the sorption onto vermiculite surface and it was inferred that the total metal uptake was distributed among four elements. � 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this study, coco-peat was tested for its potential to sorb malachite green (MG) and crystal violet (CV) from aqueous solutions. The pH edge experimental results indicated that biosorption of two cationic dyes increased with increase in pH and maximum biosorption obtained at pH 7. The Fourier transform infrared spectrometry confirmed the involvement of negatively charged groups in the removal of cationic dyes. Furthermore, the scanning electron micrographs were used to examine the surface morphology of coco-peat. The equilibrium isotherms determined at different pH conditions were described using two-parameter (Langmuir and Freundlich) and three-parameter (Sips and Redlich‐Peterson) models. According to the Langmuir model, maximum dye uptakes of 276.8 and 119.2 mg/g were obtained for MG and CV, respectively. Biosorption kinetics were modelled using pseudofirst- and pseudo-second-order models, with the former described experimental data with high correlation coefficients and low % error values. Various thermodynamic parameters such as changes in Gibbs free energy, enthalpy and entropy were calculated; and results indicated that the present system was spontaneous and endothermic process.

Green roofs have the potential to be used as a pollutant-sink in urban environments. Unfortunately, until now no systematic study has been conducted to enhance the runoff quality from green roofs. The present work investigates the viability of using low-cost aggregates along with a biosorbent (Sargassum biomass) to prepare substrate mix for extensive green roofs to improve runoff quality. We have used (on a volume basis) 30% perlite, 20% vermiculite, 10% sand, 20% crushed brick, 10% coco-peat and 10% Sargassum biomass to prepare green roof substrate. The developed green roof substrate was found to have low bulk density (487kg/m3), high water retention capacity (58.5%), air filled porosity (19.5%), and hydraulic conductivity (4195mm/h). Through laboratory packed column study, we identified superior sorption capacity of green roof substrate towards various metal ions such as Al, Fe, Cr, Cu, Ni, Zn, Cd and Pb. Roof-top experiments in pilot-scale green roof assemblies with Portulaca grandiflora as vegetation were conducted for several artificial rain events (unspiked and metal-spiked). Results based on unspiked artificial rain events suggested that concentrations of most of the chemical components in runoff were highest during the beginning of rain events and thereafter subsided during the subsequent rain events. Metal-spiked artificial rain events revealed that green roofs acted as a sink for various metal ions and generated better runoff, whose quality was significantly less than fresh water standards. Green roofs also showed the potential to neutralize the acidic nature of inlet water and delay runoff generation. Significant differences were also observed between non-vegetated and vegetated green roof assemblies in runoff quality and quantity, with the latter producing better results. � 2014 Elsevier B.V.

In this work, non-living red seaweed (Kappaphycus alvarezii) biomass was investigated as a new biosorbent of methylene blue from aqueous solution. The effect of operational parameters such as equilibrium pH, agitation time, initial dye concentrations, and biosorbent dosage on the biosorption capacity of Kappaphycus alvarezii was studied. The equilibrium solution pH was found to profoundly affect methylene blue sorption capacity of Kappaphycus alvarezii with pH 8 found to be optimum. Evidence from Fourier-transform infrared spectroscopy and scanning electron microscopy pictures confirmed the dye biosorption mechanism as electrostatic interaction between the negatively charged seaweed surface and positively charged methylene blue. Biosorption isotherms indicated that Kappaphycus alvarezii exhibited methylene blue uptake of 74.4 mg/g, according to the Langmuir model. The equilibrium isotherm data were evaluated using the Freundlich, Langmuir, Redlich-Peterson, and Toth models. Kinetic studies revealed that methylene blue uptake was fast with 97% or more of the uptake occurred within 60 min of contact time. The pseudo first and second order models were applied to describe kinetic data, of which the pseudo-first order described experimental data better with high correlation coefficient and low percentage of error values. � , Copyright � Taylor & Francis Group, LLC.

The present study examines whether green roofs act as a sink or source of contaminants based on various physico-chemical parameters (pH, conductivity and total dissolved solids) and metals (Na, K, Ca, Mg, Al, Fe, Cr, Cu, Ni, Zn, Cd and Pb). The performance of green roof substrate prepared using perlite, vermiculite, sand, crushed brick, and coco-peat, was compared with local garden soil based on improvement of runoff quality. Portulaca grandiflora was used as green roof vegetation. Four different green roof configurations, with vegetated and non-vegetated systems, were examined for several artificial rain events (un-spiked and metal-spiked). In general, the vegetated green roof assemblies generated better-quality runoff with less conductivity and total metal ion concentration compared to un-vegetated assemblies. Of the different green roof configurations examined, P. grandiflora planted on green roof substrate acted as sink for various metals and showed the potential to generate better runoff. � 2014 Elsevier Ltd. All rights reserved.

Heavy metal pollution is a major environmental concern in many countries. Among heavy metals, chromium is one of the widely used despite being one of the most toxic metal ions. The present study deals with the evaluation of Cr(VI) biosorption using a novel fresh water alga Rhizoclonium hookeri. Batch experiments were conducted and the maximum adsorption capacity was evaluated as 67.3 mg/g at pH 2 at a biomass dosage of 1 g/L and 1,000 mg/L initial Cr(VI) concentration. Fourier transform infrared spectroscopy analysis of alga before and after biosorption revealed a shift in the carboxylic O�H stretching vibration from 3,401 to 3,373 cm?1, which confirmed its involvement in biosorption of Cr(VI) by R. hookeri. Surface morphology of alga was examined using the scanning electron microscopy, which indicated the highly porous nature of biomass. Non-linear regression analyses of isotherm models revealed that the three-parameter model isotherms (Redlich�Peterson and Sips) better described the experimental data compared with two-parameter model isotherms (Langmuir and Freundlich). An analysis of the kinetic models (pseudo-first-order, pseudo-second-order and Elovich models) indicated that the experimental data followed pseudo-second-order kinetics. The thermodynamic parameters such as free energy, enthalpy and entropy were calculated and Cr(VI) biosorption was found to be a spontaneous and endothermic process. � 2014 Balaban Desalination Publications. All rights reserved.

This study examined the potential use of a range of sorbents (crab shell, chitosan, activated carbon, ion exchange resin, peat, sawdust, bagasse, Turbinaria conoides, Sargassum sp. and Ulva sp.) for simultaneous removal of 8 heavy metals from synthetic research laboratory effluents. The sorption experiments were conducted in both batch and continuous modes of operation. Among the sorbents used in this study, crab shell proved to be effective with a total biosorption capacity of 440 mg/g at pH 4.5. Continuous-flow experiments with crab shell loaded in an up-flow packed column were successful with a total biosorption capacity of 165 mg/g. The crab shell-based biosorption process was also identified to be superior to the commonly used hydroxide precipitation technique. This work reveals some practical issues associated with the biosorption process such as leaching of excess light metal ions, poor affinity toward anions and effluent odor. The study also highlights other shortcomings of biosorption, and proposes technical approaches to overcome them. � 2013 Elsevier Ltd. All rights reserved.

An eco-friendly and inexpensive technique for wastewater treatment originated from inductively coupled plasma-optical emission spectrometry (ICP-OES) is presented within this paper. The proposed process comprised of loading waste crab shells in packed column for adsorption of heavy metal ions, followed by desorption using 0.01 M HCl. An exhaustive physical and chemical characterization of ICP-OES wastewater revealed the complex nature of effluent, including the presence of 15 different metals and metalloid under strong acidic condition (pH 1.3). Based on the preliminary batch experiments, it was identified that solution pH played a major role in metal sequestration by crab shell with pH 3.5 identified as optimum pH. Rapid metal biosorption kinetics along with complete desorption and subsequent reuse for three cycles was possible with crab shell-based treatment process. Continuous flow-through column experiments confirmed the high performance of crab shell towards multiple metal ions with the column able to operate for 22 h at a flow rate of 10 mL/min before outlet concentration of arsenic reached 0.25 times of its inlet concentration. Other metal ions such as Cu, Cd, Co, Cr, Pb, Ni, Zn, Mn, Al, and Fe were only in trace levels in the treated water until 22 h. The performance of the treatment process was compared with trade effluent discharge standards, and the process flow diagram along with cost analysis was suggested.

The ability of green algal biomass of Ulva sp. to biosorb Cr(III) and Mn(II) from single- and binary- solute systems was investigated. Experimental results showed that pH 4.5 resulted in highest metal uptake by Ulva sp. biomass. Determined levels of maximum biosorption capacities were 2.89 and 1.07 mmol g−1 for Cr(III) and Mn(II), respectively, during single-solute systems. Isotherms were modeled using the Langmuir, Freundlich, and Redlich-Peterson models with the later able to describe the biosorption isotherms with high correlation coefficients and low % error values. The removal kinetics were described using pseudo -first and -second order models. Desorption was possible using 0.01 M HCl and with this elutant, Ulva sp. biomass was reused for three cycles of sorption-desorption. Experiments with binary metal solutions showed that Ulva sp. biomass preferred Cr(III) (2.03 mmol g−1) compared to Mn(II) (0.34 mmol g−1) at pH 4.5. Binary isotherms were described using the extended Langmuir, Freundlich, and Redlich-Peterson models incorporated with interaction factor. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 147–153, 2014

Disposal of eggshell wastes has become one of the most serious problems for poultry industries. Efficient utilization of eggshell wastes for other application may solve this problem. This study uses eggshell as an additive to precipitate divalent lead cations [Pb(II)] from aqueous solutions in the pH range of 2–5. Owing to high CaCO3 content, eggshell precipitates Pb(II) to form lead carbonates, which will then settle on the surface of eggshell. Scanning electron microscopy and energy dispersive X-ray analysis of the eggshell exposed to Pb(II) solutions indicated the deposition of lead carbonates on the surface of the eggshell. On reducing the particle size of an eggshell from 750 to 100 μm, the Pb(II) removal efficiency of it increased from 30.7 to 99.6% at an initial Pb(II) concentration of 1045 mg/L. It was found through isotherm experiments that eggshell powder (100 μm) was capable of sorbing 577 mg Pb/g compared with 154 mg Pb/g by eggshell particles (750 μm). The biosorption isotherms were ...

The use of different seaweeds such as Sargassum sp., Turbinaria conoides, and Ulva sp. in removing mercury(II) from aqueous solutions were investigated. The initial experimental runs, conducted at different equilibrium pH conditions, demonstrated that brown seaweeds outperformed green seaweed in Hg(II) biosorption at all pH conditions. In particular, at pH 5, maximum biosorption capacities of 170.3 and 145.8 mg/g were recorded for the brown seaweeds T. conoides and Sargassum sp., respectively, compared with 138.4 mg/g for the green seaweed Ulva sp. Isotherm data were modeled and interpreted using the Langmuir, Freundlich, Redlich-Peterson, and Toth models, with the latter described the Hg(II) isotherms with high correlation coefficients and low % error values. The kinetic data indicate the rapidity of the biosorption process, with the equilibrium achieved within 90 min. Several models, including the Elovich, pseudo-first-order, and pseudo-second-order models, were examined for their suitability w...

Starch/polyaniline nanocomposite was synthesized by chemical oxidative polymerization of aniline and was subsequently analyzed for dye removal from aqueous solution. Batch experiment results showed that nanocomposite removed 99% of Reactive Black 5, 98% of Reactive Violet 4, and decolorized 87% of dye bath effluent. The Toth isotherm model better described single component equilibrium adsorption, whereas the modified Freundlich model showed satisfactory fit for dye bath. In kinetic modeling, single system followed pseudo-second-order and dye bath followed the modified pseudo-first-order model. Fourier transform infrared spectroscopy pattern of the nanocomposite showed the participation of aromatic, amino, hydroxyl, and carboxyl groups. The results indicate that starch/polyaniline nanocomposite can be used as an effective adsorbent for removal of dyes from textile effluents.

Adsorption is a facile, economic, eco-friendly and low-energy requiring technology that aims to separate diverse compounds (ions and molecules) from one phase to another using a wide variety of adsorbent materials. To date, this technology has been used most often for removal/recovery of pollutants from aqueous solutions; however, emerging post-sorption technologies are now enabling the manufacture of value-added key adsorption products that can subsequently be used for (i) fertilizers, (ii) catalysis, (iii) carbonaceous metal nanoparticle synthesis, (iv) feed additives, and (v) biologically active compounds. These new strategies ensure the sustainable valorisation of post-sorption materials as an economically viable alternative to the engineering of other green chemical products because of the ecological affability, biocompatibility, and widespread accessibility of post-sorption materials. Fertilizers and feed additives manufactured using sorption technology contain elements such as N, P, Cu, Mn, and Zn, which improve soil fertility and provide essential nutrients to animals and humans. This green and effective approach to managing post-sorption materials is an important step in reaching the global goals of sustainability and healthy human nutrition. Post-sorbents have also been utilized for the harvesting of metal nanoparticles via modern catalytic pyrolysis techniques. The resulting materials exhibited a high surface area (>1000m2/g) and are further used as catalysts and adsorbents. Together with the above possibilities, energy production from post-sorbents is under exploration. Many of the vital 3E (energy, environment, and economy) problems can be addressed using post-sorption materials. In this review, we summarize a new generation of applications of post-adsorbents as value-added green chemical products. At the end of each section, scientific challenges, further opportunities, and issues related to toxicity are discussed. We believe this critical evaluation not only delivers essential contextual information to researchers in the field but also stimulates new ideas and applications to further advance post-sorbent applications.

Biosorption is a well established remediation technology for heavy metal ions; however, little is known about their practical applications. Effluents generated in research laboratories are creating severe treatment problems for various organizations, owing to their complex nature. This article utilizes the well-defined biosorption technology for the treatment of complex synthetic laboratory wastewaters. Three seaweeds, Sargassum, Ulva and Turbinaria were employed to remediate wastewater found to comprise of eight different heavy metal ions (Cu(II), Co(II), Cd(II), Cr(III), Ni(II), Mn(II), Pb(II) and Zn(II)) at 0.016 M total concentration. Among the seaweeds, Turbinaria conoides performed well in both batch and continuous-mode of operation with total uptake capacities of 3.20 and 3.01 mmol/g, respectively. This article also discusses mechanism of seaweeds biosorption along with the practical problems associated with biosorption process in real applications, including process design, cost, biosorbent availability, mode of operation, quality of the final effluent and ultimate disposal of biosorbent.

A complex Remazol dye effluent, comprised of Remazol Brilliant Blue R, Remazol Black, Remazol Violet, Remazol Orange, sodium chloride, sodium carbonate, sodium hydroxide, and acetic acid, was decolorized using polyaniline/extracellular polymeric substance (Pn/EPS) composite. Scanning electron micrograph showed that the surface of the composite was rough with granular appearance, providing a good possibility for dyes adsorption. X-ray diffractogram (XRD) of the composite showed the main reflections of both Pn and EPSs (2θ = 6.0, 20.1 and 26.2, 30.4, and 40.8). Experiments were carried out as a function of contact time, pH, and adsorbent dose. Under optimized conditions, the maximum percentage removal was found to be 99.8% for the complex Remazol effluent. The Freundlich isotherm model and pseudo first-order rate expression showed satisfactory fit to the equilibrium biosorption data of Pn/EPS composite. Fourier transform infrared spectroscopy, XRD, and desorption studies confirmed the involvement of aromatic, amino, hydroxyl, and carboxylic groups in dye adsorption. The results indicate that composite is suitable as an adsorbent material for the enhanced removal of dyes from complex Remazol effluent.

Green (vegetated) roofs are emerging as practical strategies to improve the environmental quality of cities. However, the impact of green roofs on the storm water quality remains a topic of concern to city planners and environmental policy makers. This study investigated whether green roofs act as a source or a sink of various metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Mn, Cr, Ni, Li and Co), inorganic anions (NO3-, NO2-, PO4(3-), SO4(2-), Cl-, F- and Br-) and cation (NH4+). A series of green roof assemblies were constructed. Four different real rain events and several artificial rain events were considered for the study. Results showed that concentrations of most of the chemical components in runoff were highest during the beginning of rain events and subsided in the subsequent rain events. Some of the important components present in the runoff include Na, K, Ca, Mg, Li, Fe, Al, Cu, NO3-, PO4(3-) and SO4(2-). However, the concentration of these chemical components in the roof runoff strongly depends on the nature of substrates used in the green roof and the volume of rain. Based on the USEPA standards for freshwater quality, we conclude that the green roof used in this study is reasonably effective except that the runoff contains significant amounts of NO3- and PO4(3-).

The present work investigated the ability of inactive brown seaweed, Turbinaria conoides, to biosorb aluminum(III) and cadmium(II) ions in both single and binary systems. Initial experiments were undertaken to determine the influence of pH and biosorption isotherms of each metallic ion. Owing to the presence of carboxylic groups, T. conoides exhibited high uptake capacity towards Al(III) and Cd(II) through ion-exchange mechanism. In the case of Al(III), T. conoides exhibited maximum biosorption at pH 4 with a capacity of 2.37 mmol/g, whereas the highest Cd(II) biosorption occurred at pH 5 with a capacity of 0.96 mmol/g. For both metal ions, T. conoides exhibited fast kinetics. Several models were used to describe isotherm (Langmuir, Freundlich, Redlich-Peterson, and Toth) and kinetic (pseudo-first and pseudo-second order) data. Desorption and reuse of T. conoides biomass in three repeated cycles was successful with 0.1 M HCl as elutant. In binary systems, the presence of Cd(II) severely affected Al(III) uptake by T. conoides. Compared to single-solute systems, Al(III) uptake was reduced to 56% compared to only 27% for Cd(II). Based on the model parameters regressed from the respective monometal systems, multicomponent Langmuir and Freundlich models were used to predict binary (Al + Cd) system of which the multicomponent Freundlich model was able to describe with good accuracy.

A novel method is presented for pyrolyzing and activating waste tires for adsorptive removal of aqueous contaminants. The adsorption characteristics of a cationic dye (methylene blue, MB) by pyrolytic tire char were evaluated. Mechanistic insights into the adsorption of MB onto char made from pyrolyzed tires are discussed on the basis of equilibrium and kinetic studies. A comparative evaluation of the performance of unoxygenated, pyrolyzed chars (NoPPO) and oxygenated chars (P550250) is reported. Despite having similar surface areas between the oxygenated and unxoygenated chars, the adsorption capacity of the former was much higher than that of the latter. However, adsorption of MB is thermodynamically unfavorable (ΔG>0) although oxygenation lowers the free energy of adsorption. MB sorption onto P550250 is inhibited by an external film, which was not observed in the case of NoPPO. An increase in the solution temperature was found to reduce the adsorption rates of MB onto P550250 but increase the sorption ...

Three seaweed species (Turbinaria conoides, Sargassum sp., and Ulva sp.) were examined to assess their ability to sequester antimonite [Sb(III)] ions from aqueous solution. Among these species, both T. conoides and Sargassum sp. showed higher Sb(III) biosorption potential than Ulva sp. The pH-edge experimental results revealed the involvement of negatively charged groups in the biosorption of Sb(III). Biosorption isotherms obtained at pH 6 indicated that T. conoides provided higher uptake of Sb(III) (18.1 mg/g) than Sargassum sp. (14.9 mg/g) according to the Langmuir model. Kinetic studies indicated that the rates of Sb(III) removal by both brown seaweeds were high, with 95% of the process completed within 45 min. A pseudo-first-order model was found to describe the kinetic data satisfactorily with a high correlation coefficient and low percentage errors. Desorption experiments with 0.1 M HCl showed that it is possible to regenerate T. conoides for its continued use as a biosorbent for up to three sorptio...

Uptake of two widely studied microcystins (MCs), microcystin-LR (MCLR) and microcystin-RR (MCRR), by peat was investigated under various environmental conditions. MCRR showed better removal (98.6 μg/g) compared to MCLR (87.8 μg/g) in a binary system. The uptake was very rapid with 90% of the toxins being removed from the aqueous phase in initial 15 min of contact. Acidic pH was slightly favorable for the uptake, but removal of MCLR and MCRR can also be achieved in neutral pH. Adsorption isotherm and kinetic modelling provided insights into the simultaneous sorption of MCLR and MCRR onto peat. The influence of various counter ions in the aqueous solution on the adsorptive removal of MCs by peat was investigated under different environmental conditions. Leaching studies showed about 50% of the toxins get desorbed at high alkaline pH. Temperature did not have much effect on either the uptake or the leaching process. The potential of peat to sequester MCs from real reservoir waters was studied to validate the optimized sorption process.

In the present study, the potential of a new brown marine alga, Turbinaria conoides , in biosorption and subsequent bioreduction of Au(III) was explored. The biosorption process was found to be rapid and completed within 60 min of contact. Also, the solution pH strongly affected Au(III) biosorption by T. conoides , with maximum uptake of 34.5 mg/g being observed at pH 2 according to the Langmuir model. Biosorption mechanism was proposed to involve electrostatic interactions between gold anions and algal functional groups, which implies that when virgin T. conoides was exposed to gold solution, AuCl 4 − anion binds to positively charged functional groups, such as amino groups (NH 2 ), on the algal surface. After 60 min, T. conoides reduced Au(III) to gold nanoparticles. Hydroxyl groups present in the brown algal polysaccharides were involved in the bioreduction of Au(III) to Au(0). The field emission scanning electron micrographs showed uniformly scattered nanoparticles with sporadic aggregation on the surface of T. conoides . XRD diffraction patterns of gold-loaded T. conoides also confirmed that the Au(III) bound on the cell wall of the biomass had been reduced to Au(0). The UV–vis spectra results indicated that the reaction solution had an absorption maximum at about 540 nm attributable to the surface plasmon resonance band of the gold nanoparticles.

The present study elucidates the underlying mechanisms involved in the interaction of lanthanides (lanthanum, cerium, europium and ytterbium) with a brown marine alga, Turbinaria conoides in quaternary mixtures. Competition between the lanthanides in occupying the binding sites of T. conoides was clearly identified, which was due to competitive ion-exchange mechanism. This competition affected the affinity of T. conoides towards each lanthanide. In comparison to single-component lanthanide system, uptake capacities in quaternary systems decreased by 75.8, 72.5, 65.0 and 70.2% for La, Ce, Eu and Yb, respectively. Biosorption mechanism was confirmed through SEM/EDX and pH-edge data, which implies that when virgin T. conoides are exposed to lanthanide solutions, La3+ cations may replace some of the alkali and alkaline earth metals naturally present in the cell wall through ion-exchange mechanism; and this phenomenon was favored at pH 5, under examined conditions. Quaternary biosorption isotherms were successfully modeled using the extended Langmuir model with a constant interaction factor. The model predictions agreed well with the experimental data. The magnitude of Eu competition over lanthanides was significant, yielding a lowest interaction factor (η = 0.91) for Eu over other lanthanides. Biosorption kinetics revealed that more than 91% of sorption process was completed within 60 min for all lanthanides, followed by slow attainment of equilibrium in around 3 h. Desorption was successful with 0.05 M HCl and the algal biomass was reused for three cycles without significant loss in original lanthanide uptake capacity.

This work explores the potential of crab ( Portunus sanguinolentus ) shell particles for the removal of manganese(II) and zinc(II) ions from aqueous solutions. The removal of metal ions by crab shell was found to be pH dependent, with optimum sorption occurring at pH 6 for both Mn(II) and Zn(II). The mechanism of metal removal by crab shell was identified as micro-precipitation of metal carbonates followed by adsorption onto chitin at the surface of crab shell, which was confirmed by pH edge and EDX analysis. The process of metal biosorption was rapid (90% removal in 120 min for Mn(II) and 90% removal in 90 min for Zn(II)) at an initial metal concentration of 500 mg/L. Modeling results revealed that Mn(II) and Zn(II) kinetics data were successfully described using pseudo-first and -second order models, compared to the Elovich equation. Furthermore, isotherm experiments revealed that crab shell possesses high uptake capacities of 69.9 and 123.7 mg/g for Mn(II) and Zn(II), respectively, according to the Langmuir model. Possibility of desorption and subsequent reuse of crab shell was attempted using 0.1 M HCl as elutant and the results were successful with the elutant exhibiting more than 99% elution efficiency for both Mn(II) and Zn(II).

The ability of crab shell to biosorb two rare earth elements (REE), namely cerium(III) and europium(III) from single and binary systems has been studied. Crab shell majorly comprised of calcium carbonate, protein and chitin. Experiments to identify the role of these constituents in REE biosorption revealed that calcium carbonate was mainly responsible for REE removal. Microprecipitation of REE by carbonate ions and subsequent settling on the surface of crab shell was identified as major mechanism responsible for crab shell biosorption performance. At optimum pH of 6, in single component system, crab shell exhibited maximum Ce(III) and Eu(III) uptakes of 144.9 and 49.5 mg/g, respectively, according to the Langmuir model. In binary systems, both Ce(III) and Eu(III) compete with each other resulted in decreased uptake. In an attempt to model the binary biosorption data, Sheindorf–Rebhun–Sheintuch equation provided more accurate prediction of isotherm data compared to extended Langmuir model with constant interaction factor. Kinetic experiments revealed that equilibrium was attained in 60 min, followed by complete saturation in 2 h, for both Ce(III) and Eu(III). Pseudo-first order model better predicted the kinetic data with high correlation coefficients and low % error values than pseudo-second order model.

The possibility of using the sorption technology to reduce the levels of metal ions present in urban storm-water runoff was investigated in this study. Seven sorbent materials including Amberlite XAD7, chitosan, crab shell, peat, Sargassum, sawdust, and sugarcane bagasse were initially examined for removal of 11 metal ions (Na, K, Ca, Mg, Mn, Co, Ni, Cu, Zn, Cd, and Pb) from simulated storm-water runoff at different concentrations. Among these sorbents, crab shell performed well with removal efficiencies exceeding 93% for all heavy metal ions examined and thus selected for further studies. Based on scanning electron microscopy/energy-dispersive x-ray analysis, microprecipitation of metal carbonates followed by adsorption onto the surface of crab shell was identified as the major mechanism responsible for removal of heavy metal ions by crab shell. Crab shell exhibited rapid removal of meal ions with attainment of biosorption equilibrium within 20 min. A crab-shell-packed column was used to study the contin...