Fine-tuning the dye adsorption capacity of UiO-66 by a mixed-ligand approach.

The mixed ligand synthetic approach offers an alternative to engineering a specific character in metal-organic framework (MOFs) materials. Herein, we synthesized and characterized a well-known prototype zirconium-based-MOF, so-called UiO-66, and its mixed ligand derivatives UiO-66-xATA, where x is mole fraction (0.5, 0.75, and 1.0) and ATA is 2-animoterephthalate. The study investigates whether the dye adsorption capacity can be tuned/enhanced by the ATA ligand substitution into the framework. We found that, at room temperature, UiO-66-0.75ATA shows the highest adsorption capacity toward various dye solutions, including methylene blue (MB), indigo carmine (IC), and congo red (CR). The optimum adsorption conditions in all four materials were in a common trend where their adsorption capacities can be increased with decreasing pH and adsorbent dose, increasing IC concentration, contact time, and temperature. Pseudo-second order kinetics model fits best with their adsorption data, where UiO-66-ATA has the fastest adsorption rate. Langmuir and Freundlich isotherms were found best to describe adsorption behavior in ATA-containing UiO-66 and UiO-66, respectively, where adsorption processes were found to be physisorption. Confirming by thermodynamic studies, the adsorption in all four materials occurred spontaneously, driven by entropy. Computational studies showed ligand to metal charge transfer where the distribution of electron densities was varied with the amount of functionalized ligand. Adsorption mechanism is proposed as a synergistic interplay between electrostatic interaction and hydrogen bonding. The findings in this work broaden the potential strategy to fine-tune the dye adsorption capacity in MOF materials.

Cellulose and hemicellulose recovery from oil palm empty fruit bunch (EFB) fibers and production of sugars from the fibers.

A sequential two-step treatment with peracetic acid (PA) and alkaline peroxide (AP) at mild temperatures (20-35°C) removed more than 98% of the lignin from oil palm empty fruit bunch (EFB) fiber. For each kilogram of EFB fiber treated, 200-250g of a solids fraction and 120-170g of a precipitate fraction were recovered after the treatment. Subsequent enzymatic hydrolysis (45°C, 72h) of the recovered solids (excluding the precipitate) resulted in a glucose yield of 629.8±0.5g per kg of the original dry EFB biomass. Enzymatic hydrolysis of untreated EFB yielded only 3.0±0.0g glucose per kg of dry EFB. Therefore, the PA-AP pretreatment enhanced glucose recovery from EFB by nearly 210-fold. The total treatment time was 93h (a 9h PA treatment at 35°C, a 12h treatment with AP (20°C, 4% NaOH), 72h of enzymatic hydrolysis).

Dynamic modelling of high biomass density cultivation and biohydrogen production in different scales of flat plate photobioreactors.

This paper investigates the scaling-up of cyanobacterial biomass cultivation and biohydrogen production from laboratory to industrial scale. Two main aspects are investigated and presented, which to the best of our knowledge have never been addressed, namely the construction of an accurate dynamic model to simulate cyanobacterial photo-heterotrophic growth and biohydrogen production and the prediction of the maximum biomass and hydrogen production in different scales of photobioreactors. To achieve the current goals, experimental data obtained from a laboratory experimental setup are fitted by a dynamic model. Based on the current model, two key original findings are made in this work. First, it is found that selecting low-chlorophyll mutants is an efficient way to increase both biomass concentration and hydrogen production particularly in a large scale photobioreactor. Second, the current work proposes that the width of industrial scale photobioreactors should not exceed 0.20 m for biomass cultivation and 0.05 m for biohydrogen production, as severe light attenuation can be induced in the reactor beyond this threshold.

Process and reactor design for biophotolytic hydrogen production.

The green alga Chlamydomonas reinhardtii has the ability to produce molecular hydrogen (H2), a clean and renewable fuel, through the biophotolysis of water under sulphur-deprived anaerobic conditions. The aim of this study was to advance the development of a practical and scalable biophotolytic H2 production process. Experiments were carried out using a purpose-built flat-plate photobioreactor, designed to facilitate green algal H2 production at the laboratory scale and equipped with a membrane-inlet mass spectrometry system to accurately measure H2 production rates in real time. The nutrient control method of sulphur deprivation was used to achieve spontaneous H2 production following algal growth. Sulphur dilution and sulphur feed techniques were used to extend algal lifetime in order to increase the duration of H2 production. The sulphur dilution technique proved effective at encouraging cyclic H2 production, resulting in alternating Chlamydomonas reinhardtii recovery and H2 production stages. The sulphur feed technique enabled photobioreactor operation in chemostat mode, resulting in a small improvement in H2 production duration. A conceptual design for a large-scale photobioreactor was proposed based on these experimental results. This photobioreactor has the capacity to enable continuous and economical H2 and biomass production using green algae. The success of these complementary approaches demonstrate that engineering advances can lead to improvements in the scalability and affordability of biophotolytic H2 production, giving increased confidence that H2 can fulfil its potential as a sustainable fuel of the future.