Sorption of copper by chemically modified aspen wood fibers

Sorption of copper (Cu2+) by untreated and treated (bleaching and hydrolysis) aspen wood fibers, cellulose and lignin was examined to understand the Cu2+ sorption behavior by these natural sorbents. All sorbents were characterized by solid-state 13C NMR and FTIR. Bleaching broke up aromatic structures and increased hydrophilicity of the fibers, whereas hydrolysis decreased carbohydrate content, producing a more hydrophobic structure. Copper sorption was a function of pH; the percentage of Cu2+ sorption steadily increased from pH 1.5 to 4.5 with a maximum sorption amount at around pH 5.5 for all the materials. All isotherms fitted well to the Langmuir equation. Bleached sample (BL) had a highest sorption capacity, followed by untreated (UTR), cellulose (CEL), and hydrolyzed (HHY), while lignin (LIG) had little Cu2+ sorption under the studied conditions. The results suggested that carboxyl (-COOH) and hydroxyl (-CHOH) in carbohydrates are mainly responsible for Cu2+ sorption, and that ion exchange may be a main sorption mechanism for the studied sorbents. Additionally, the sorption capacity for Cu2+ on all sorbents decreased with the increase of the initial concentrations of Ca2+, Na+ or Al3+. Copper sorption decreased rapidly at low initial concentrations of Ca2+, Na+ or Al3+. However, the decline of Cu2+ sorption slowed down when initial Na+ and Ca2+ concentration was higher than 0.05 M or initial Al3+ concentration was greater than 0.005 M, indicating that specific adsorption may be taking place. Therefore, the majority of sorbed Cu2+ to aspen wood fibers could be through ion exchange (especially, for UTR, BL and CEL), while a faction of sorbed Cu2+ via inner-sphere complex (or specific adsorption). © 2009 Elsevier Ltd. All rights reserved

Permeable Pavements as Sustainable Nature-Based Solutions for the Management of Urban Lake Ecosystems

Permeable pavement systems (PPS) are becoming integral parts of the urban green infrastructure (UGI) planning approaches for the implementation of nature-based solutions (NbS) especially in rapidly developing regions. Global research has demonstrated that UGI is quite essential to regulate and establish the hydrological and ecological functions of urban aquatic ecosystems such as lakes. At a micro-scale level, design of storm water management systems requires detailed planning, as urban flooding has the potential to affect a huge population dwelling in the cities often without any warning. Such events cause drastic changes in the hydrological statuses of urban lakes, by gradually decreasing their natural resilience over a period. An associated risk with the degradation of urban lake systems pertains to their immense contributions in maintaining the ambient temperature profiles. The loss of the urban lake systems will directly lead to a substantial rise in the ambient air temperature and enhanced heat island effect. PPS can offer successful NbS to improve the resilience of the lake systems. PPS would also prove to be instrumental in mitigating the urban heat island effects by intercepting the excessive run-offs, increasing green water collection and storage, as well as by maintaining close-to-natural flow regimes in the case of urban lakes. Such micro-scale NbS offered by the design and implementation of PPS can offer huge environmental, social, and economic benefits in the long run. PPS can also offer direct benefits towards regulating the lake services and can assist in addressing the sustainable development goals for the lake ecosystems in the urban set-up, which are under stress due to various anthropogenic detrimental activities