Removal of Toxic Heavy Metals from Contaminated Aqueous Solutions Using Seaweeds: A Review

Heavy metal contamination affects lives with concomitant environmental pollution, and seaweed has emerged as a remedy with the ability to save the ecosystem, due to its eco-friendliness, affordability, availability, and effective metal ion removal rate. Heavy metals are intrinsic toxicants that are known to induce damage to multiple organs, especially when subjected to excess exposure. With respect to these growing concerns, this review presents the preferred sorption material among the many natural sorption materials. The use of seaweeds to treat contaminated solutions has demonstrated outstanding results when compared to other materials. The sorption of metal ions using dead seaweed biomass offers a comparative advantage over other natural sorption materials. This article summarizes the impact of heavy metals on the environment, and why dead seaweed biomass is regarded as the leading remediation material among the available materials. This article also showcases the biosorption mechanism of dead seaweed biomass and its effectiveness as a useful, cheap, and affordable bioremediation material.

Synthesis of Polyurethane Membranes Derived from Red Seaweed Biomass for Ammonia Filtration

The development of membrane technology is rapidly increasing due to its numerous advantages, including its ease of use, chemical resistant properties, reduced energy consumption, and limited need for chemical additives. Polyurethane membranes (PUM) are a particular type of membrane filter, synthesized using natural organic materials containing hydroxy (-OH) groups, which can be used for water filtration, e.g., ammonia removal. Red seaweed (Rhodophyta) has specific molecules which could be used for PUM. This study aimed to ascertain PUM synthesis from red seaweed biomass (PUM-RSB) by using toluene diisocyanate via the phase inversion method. Red seaweed biomass with a particle size of 777.3 nm was used as starting material containing abundant hydroxy groups visible in the FTIR spectrum. The PUM-RSB produced was elastic, dry, and sturdy. Thermal analysis of the membrane showed that the initial high degradation temperature was 290.71 °C, while the residue from the thermogravimetric analysis (TGA) analysis was 4.88%. The PUM-RSB section indicates the presence of cavities on the inside. The mechanical properties of the PUM-RSB have a stress value of 53.43 MPa and a nominal strain of 2.85%. In order to optimize the PUM-RSB synthesis, a Box–Behnken design of Response Surface Methodology was conducted and showed the value of RSB 0.176 g, TDI 3.000 g, and glycerin 0.200 g, resulting from the theoretical and experimental rejection factor, i.e., 31.3% and 23.9%, respectively.

Landing facilities for processing of cultivated seaweed biomass: a Norwegian perspective with strategic considerations for the European seaweed industry

The production of marine biomass based on seaweed cultivation is growing rapidly in Europe. One of the major challenges for the development of this new industry is associated with processing of the wet biomass harvested from cultivation sites. Efficient methods for the stabilization (i.e. procedures to maintain the integrity and safety of the biomass) and further processing of large quantities of harvested raw material are still lacking as the development of adapted technologies is often limited by significant capital investment. This study investigates the concept of landing facilities for the processing of cultivated seaweed biomass (LFCS) shared among various stakeholders as a practical mean to overcome these challenges. Qualitative data were collected during interviews with relevant stakeholders from Norway and abroad (including seaweed cultivators, technology suppliers and industrial buyers of biomass) to describe the current commercial applications for cultivated seaweeds as well as the methods used for the stabilization and processing of the biomass. This study showed that LFCS can give stakeholders the opportunity to share the costs (investment, operational), thus lowering the financial threshold for establishing efficient strategies for processing large quantities of cultivated seaweed biomass. It was identified that such a structure will increase the synergy among industrial actors along the entire value chain to stimulate innovation and facilitate the production of high-quality products from seaweeds to relevant markets (food, animal feed, nutraceuticals and cosmetics). It can also lead to a higher degree of specialization in this new industry. These premises will contribute to increase the profitability of the emerging European seaweed sector. Identification of the appropriate stabilization processes for large-scale production, definition of the role of LFCS in the seaweed value chain as well as the mode of engagement of the stakeholders in such structure are thus acknowledged as key considerations to define during the planning phase.

Optimization of Polyurethane Membrane Physical Characteristics of Red Seaweed Biomass Using a Box-Behnken Design

The polyurethane membrane is used as a separator either by filtration or adsorption, and this process is significantly affected by its strength and physical condition. We synthesized polyurethane membranes using red seaweed with Gracilaria sp as a hydroxyl source. The Box-Behnken Design of the Response Surface Methodology (RSM) using Software Design Expert Version 10.0.3.0 with three factors (TRL, TDI, and Glycerin). The F-value of 0.42 suggests that the membrane is less fit, while the P-value of 75.10% indicates that the quadratic design model is suitable for data analysis of physical characteristics. The optimal physical characteristics were obtained at a composition of 0.233 g TRL, 2.675 g TDI, and 0.254 g glycerin with a physical point of 6.5 (strong and elastic). Optimal polyurethane membrane has good thermal and mechanical properties at temperatures of Tg 58 °C, Tm 322 °C, and Td 534 °C, as well as stress and nominal strain values of 69.3 MPa and 5.74%. Polyurethane membrane synthesized from red seaweed has good physical properties. The result of this research is the basis for the development of polyurethane membrane applications from red seaweed.

Effects of outplanting time on growth, shedding and quality of Saccharina latissima (Phaeophyceae) in its northern distribution range

To reach the goal of large-scale seaweed cultivation in Norway and the rest of Europe, new knowledge about the commercially important kelp speciesSaccharina latissimais needed. Efforts to maximise biomass by outplanting the seaweed in different seasons can affect seaweed quality. Here, we investigate the effects of outplanting time (February, April, and May) when cultivatingS. latissimain the northern range of the species’ distribution. We studied the quantity and quality of the seaweed biomass produced in the autumn following outplanting. Effects on quantity were evaluated as seaweed frond area, relative daily growth rate (DGR) and relative daily shedding rate (DSR). Quality was evaluated by tissue content of carbon and nitrogen compounds and number of fouling epizoans. Cultivation was successful when seedlings were outplanted in both February and April, but not in May. An earlier outplanting, in February, gave a prolonged time for grow-out at sea prior to the main recruitment event of epizoans that occurred in September, thereby earlier outplanting resulted in larger frond areas. The frond area reached in September was doubled when seedlings were outplanted in February compared to April, whereas a later outplanting in April gave a higher DGR and DSR, higher carbon content, and lower amount of fouling epizoans. The outplanting season did not affect tissue nitrate concentration or internally stored nitrate. These results show that outplanting time is an important factor to consider especially for biomass yield, but also for seaweed quality, including epibiosis of the seaweed biomass.