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Natural Materials – Composition and Combinations
Published in Graham A. Ormondroyd, Angela F. Morris, Designing with Natural Materials, 2018
Hydrated silica (SiO2·nH2O) is found in diatom skeletons and sea sponge spicules. In the diatoms, the silica structures (frustules) may take amazing intricate patterns (Round et al. 1990), with a porous valve face-controlling uptake of particles from the environment (Hale and Mitchell 2001). The structures and forms have provided stimulus for design and architecture (Kooistra and Pohl 2015). Sea sponge skeletons further demonstrate the potential of silica to construct intricate and mechanically efficient structures (Figure 3.15). These intricate basket-like structures are built up using fine filaments which have concentric layers of silica with a small proportion of organic material providing interlayers (Woesz et al. 2006). The hexactinellida and demospongiae classes of sea sponges construct their skeletons from silica, while the calcarea, another class, use calcium carbonate. Spongin, a collagenous protein, may also be used to form the skeleton of the demospongiae, either with the silica deposits or without – in this case, the spongin provides greater flexibility and the sponge has a different form.
A critical review on remediation of bisphenol S (BPS) contaminated water: Efficacy and mechanisms
Published in Critical Reviews in Environmental Science and Technology, 2020
Zheng Fang, Yurong Gao, Xiaolian Wu, Xiaoya Xu, Ajit K. Sarmah, Nanthi Bolan, Bin Gao, Sabry M. Shaheen, Jörg Rinklebe, Yong Sik Ok, Song Xu, Hailong Wang
Adsorption may play an important role in the BPS biodegradation process. In activated carbon amended constructed wetlands, BPS was firstly adsorbed by activated carbon then biodegraded by attached-bacteria (Wirasnita et al., 2018). The large surface area and highly porous structure of activated carbon can not only adsorb more BPS that is used as a carbon source of degrading bacteria but also can also generate a complex and large bacterial population. Besides, the abundance analysis of 16S rRNA genes suggests that constructed wetlands amended with activated carbon grow much more bacterial population (3.7 × 107 to 2.8 × 109 copies/g) than that of pumice rock (2.8 × 105 to 1.6 × 107 copies/g), leading to a much higher degradation efficiency of BPS. In the laccase biodegradation system, the adsorption of BPS onto Hippospongia communis spongin scaffolds improves BPS biodegradation (Zdarta et al., 2018).
Developments in enzyme and microalgae based biotechniques to remediate micropollutants from aqueous systems—A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Zeba Usmani, Minaxi Sharma, Tiit Lukk, Yevgen Karpichev, Vijay Kumar Thakur, Vivek Kumar, Abdelmounaaim Allaoui, Abhishek Kumar Awasthi, Vijai Kumar Gupta
Although the usage of enzymes has many advantages in the remediation of micropollutants, there is always a possibility of their inactivation by various denaturants and inhibitors which may affect their reusability. To combat these drawbacks, various immobilizations methods such as covalent bonding, bonding to magnetic nanoparticles for easier separation and higher surface area (Fortes et al., 2017), adsorption, entrapment, enzymatic encapsulation (Le et al., 2016) and cross-linking enzyme aggregates (CLEA) to achieve desired properties (Kumar & Cabana, 2016) have been developed. Immobilized systems are a better choice over free enzymes due to easy separation, improved reusability and higher stability (pH, temperature and longevity) (Mardani et al., 2018). However, it is important to validate the effectiveness of immobilization systems since they modify enzymatic structure slightly which may lead to blocking of the enzyme active site (Barrios-Estrada et al., 2018). Immobilized laccase on chitosan/polyamide nanofibers using spacers, was found to be more effective than free enzymes at transforming 17α-Ethinylestradiol and BPA (Maryšková et al., 2016). Similarly, BPS which is almost non-biodegradable in laccase of T. versicolor, was found to degrade by 47% on laccase immobilized on Hippospongia communis spongin scaffolds (Fang et al., 2020). This could be due to higher surface area available for the adsorption of the micropollutants onto the immobilization material. García-Morales et al. (2018) reported that laccase immobilized on titania nanoparticles performed better at remediating diclofenac and acetaminophen due to the availability of larger surface area for enhanced enzyme loading.