Design and assessment of an energy self-supply process producing tetraethyl orthosilicate using rice husk

One-Step Esterification of Phosphoric, Phosphonic and Phosphinic Acids with Organosilicates: Phosphorus Chemical Recycling of Sewage Waste

Global concerns regarding the depletion and strategic importance of phosphorus resources have increased demand for the recovery and recycling. However, waste-derived phosphorus compounds, primarily as chemically inert phosphoric acid or its salts, present a challenge to their direct conversion into high-value chemicals. We aimed to develop an innovative technology that utilizes the large quantities of sewage waste, bypasses the use of white phosphorus, and enables esterification of phosphoric acid to produce widely applicable phosphate triesters. Tetraalkyl orthosilicates emerged as highly effective reagents for the direct triple esterification of 85 % phosphoric acid, as well as the esterification of organophosphinic and phosphonic acids. Furthermore, we achieved esterification of recovered phosphoric acid with tetraalkyl orthosilicate, thus pioneering a recycling pathway from sewage waste to valuable phosphorus chemicals. Experimental and theoretical investigations revealed a novel mechanism, wherein tetraalkyl orthosilicates facilitate multimolecular aggregation to achieve alkyl transfer from tetraalkylorthosilicate to phosphoric acid via multiple proton shuttling.

Polyethylene Glycol/Rice Husk Ash Shape-Stabilized Phase Change Materials: Recovery of Thermal Energy Storage Efficacy via Engineering Porous Support Structure

This study focuses on modifying the porous structure of acid-treated rice husk ash (ARHA) to enhance the thermal energy storage capacity of poly(ethylene glycol) (PEG) confined within shape-stabilized phase change materials. The modification process involved a cost-effective sol-gel method in which ARHA was initially dissolved in an alkaline solution and subsequently precipitated in an acidic environment. ARHA, being a mesoporous SiO2-based material with a high surface area but low pore volume, had limited capacity to adsorb PEG (50%). Furthermore, it hindered the crystallinity of impregnated PEG by fostering abundant interfacial hydrogen bonds (H-bonds), resulting in a diminished thermal energy storage efficiency. Following modification of the porous structure, the resulting material, termed mARHA, featured a three-dimensional macroporous network, providing ample space to stabilize a significant amount of PEG (70%) without any leakage. Notably, mARHA, with a reduced surface area, effectively mitigated interfacial H-bonds, consequently enhancing the crystallinity of impregnated PEG. This modification led to the recovery of thermal energy storage efficacy from 0 J/g for PEG/ARHA to 109.3 J/g for PEG/mARHA. Additionally, the PEG/mARHA composite displayed improved thermal conductivity, reliable thermal performance, and effective thermal management when used as construction materials. This work introduces a straightforward and economical strategy for revitalizing thermal energy storage in PEG composites confined within RHA-based porous supports, offering promising prospects for large-scale applications in building energy conservation.

A novel cetyltrimethylammonium bromide-based deep eutectic solvent pretreatment of rice husk to efficiently enhance its enzymatic hydrolysis

Deep eutectic solvent (DES) has caught widely attention of researchers in biomass pretreatment. As a highly efficient surfactant, cetyltrimethylammonium bromide (CTAB) was expected to be used for synthesizing new DESs with additional functions in pretreatment. In this work, an efficient pretreatment method using a mixture of CTAB and lactic acid (LA) as a novel functional DES was established to improve enzymatic digestion efficiency of rice husk (RH). The results showed that DES CTAB:LA effectively removed lignin (51.5%) and xylan (79.9%) and the enzymatic hydrolysis activity of CTAB:LA-treated RH was 5 times that of RH. Then, a series of characterization demonstrated that a substantial accessibility increased, a hydrophobicity and lignin surface area decreased, and great surface morphology alternation were observed on the treated RH, which explained the increase in enzymatic hydrolysis efficiency. Overall, the discovery of more functional DESs might be motivated and biorefinery pretreatment processes might be greatly promoted.