Valorization of loquat seeds by hydrothermal carbonization for the production of hydrochars and aqueous phases as added-value products

In the framework of circular bio-economy, waste loquat seeds were utilized for the production of two added-value products. The seeds were hydrothermally carbonized at a temperature range of 150-250 °C and time range 2-6 h and the resultant hydrochars and aqueous phases were characterized using various methods. The optimum higher heating value of 30.64 MJ kg-1, ash content of 1.99 wt % and alkali index of 0.05 were achieved for the hydrochar prepared at 250 °C and 6 h, establishing its suitability for energy-related applications. The aqueous phase obtained at 250 °C and 6 h achieved 90% scavenging of the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical and had a IC50 value of 43.71 μg mL-1. Principal component analysis showed that the production of phenols, ketones, alkenes and organic acids was favored at >200 °C, whereas furans and aldehydes were primarily formed at 150 °C. Conclusively, both added-value products were obtained at the same optimum hydrothermal carbonization conditions of 250 °C and 6 h treatment time. In a bio-refinery context, this has the practical implication that both bio-products be obtained simultaneously, without the need to switch between different temperatures and residence times.

Combining geophysics and material science for environmental remediation: Real-time monitoring of Fe-biochar arsenic wastewater treatment

In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 mg L^-1) from a laboratory-prepared wastewater. The wastewater treatment process was monitored in real-time by spectral induced polarization (SIP), over a wide range of frequencies (0.01-1000 Hz). Both 5 and 10% biochar-amended columns achieved As removal exceeding 98%. The SIP parameters appear to be sensitive on As removal processes, with the recorded trend following the conventional geochemical monitoring, while offering higher temporal resolution.

Glycine Betaine Accumulation, Significance and Interests for Heavy Metal Tolerance in Plants

Unexpected biomagnifications and bioaccumulation of heavy metals (HMs) in the surrounding environment has become a predicament for all living organisms together with plants. Excessive release of HMs from industrial discharge and other anthropogenic activities has threatened sustainable agricultural practices and limited the overall profitable yield of different plants species. Heavy metals at toxic levels interact with cellular molecules, leading towards the unnecessary generation of reactive oxygen species (ROS), restricting productivity and growth of the plants. The application of various osmoprotectants is a renowned approach to mitigate the harmful effects of HMs on plants. In this review, the effective role of glycine betaine (GB) in alleviation of HM stress is summarized. Glycine betaine is very important osmoregulator, and its level varies considerably among different plants. Application of GB on plants under HMs stress successfully improves growth, photosynthesis, antioxidant enzymes activities, nutrients uptake, and minimizes excessive heavy metal uptake and oxidative stress. Moreover, GB activates the adjustment of glutathione reductase (GR), ascorbic acid (AsA) and glutathione (GSH) contents in plants under HM stress. Excessive accumulation of GB through the utilization of a genetic engineering approach can successfully enhance tolerance against stress, which is considered an important feature that needs to be investigated in depth.

Subcritical water treatment of landfill leachate: application of response surface methodology

CONTEXT

Leachate is the liquid formed when waste breaks down in the landfill and water filters through that waste. This liquid is highly toxic and can pollute the land, ground water and water ways. It is mandatory for landfills to protect against leachate in most countries worldwide. Controlling the pollutant loading, means reducing its quantity by containing or treating the waste to comply with certain discharge characteristics which are compatible with the receptor medium.

OBJECTIVE

This paper describes the reduction of the organic load of a mature landfill leachate using a novel experimental set-up that employs hydrogen peroxide under subcritical conditions and aims to establish this method as an effective alternative to currently used options. Response surface methodology was applied to optimize the treatment process and determine which of the following there parameters - temperature, residence time and hydrogen peroxide concentration - played the most important role.

METHOD

The method employed is based on the use of laboratory-scale, stainless steel reactors, filled with the leachate and appropriate quantities of hydrogen peroxide. Under subcritical conditions (temperature in the range of 100-374 °C and enough pressure to maintain the liquid state of water), hydrogen peroxide produces hydroxyl radicals which are highly reactive and oxidize the organic molecules of the leachate.

RESULTS

The highest COD decrease of 85% was experimentally observed at 300 °C, 500 mM H2O2 and 180 min residence time. It was determined that the combination of oxidant concentration and temperature is the rate-determining factor, whereas residence time has a lesser effect on the process.

CONCLUSIONS

A simple, quick, effective and environmentally-friendly method for the treatment of the organic load of landfill leachate was developed and optimized at laboratory scale.