Effects of organosilicon on the physicochemical properties of acidic and saline-alkaline soils and the flocculation kinetics of clay particles

Abstract

Organosilicon compounds, ubiquitously employed in agricultural, industrial, and environmental remediation, exhibit persistent soil accumulation behaviors. Understanding how these compounds affect acidified and saline-alkaline soils is essential for evaluating their ecological impacts and optimizing their application. This study investigated the effects of four organosilicon compounds dimethyl dichlorosilane (DMDCS), dodecamethylcyclohexasiloxane (D6), polydimethylsiloxane (PDMS), and γ-(methacryloyloxy) propyltrimethoxysilane (KH-570)-on the physical and chemical properties of acidic red soil and saline-alkaline soil. Through integrated dynamic light scattering analysis and controlled incubation experiments, we systematically investigated soil structural modification, clay flocculation dynamics, and cadmium adsorption behavior. Results showed DMDCS lowered pH and cation exchange capacity (CEC) in soils, with maximum reductions of 0.88 and 6.5 cmol/kg (red soil) and 0.52 and 9.7 cmol/kg (saline-alkaline soil). KH-570 increased pH and CEC, with maximum increases of 0.10 and 4.2 cmol/kg (red soil) and 0.15 and 6.4 cmol/kg (saline-alkaline soil). DMDCS reduced Cd adsorption by 57.25 % in red soil and 21.28 % in saline-alkaline soil, while D6 and KH-570 enhanced Cd adsorption. Flocculation studies showed that organosilicon compounds promoted clay particle aggregation, with DMDCS having the strongest effect. DMDCS and KH-570 improved soil structure, while D6 and PDMS had little impact. These findings establish structure-activity relationships between organosilicon functionalities and soil modification effects, providing a mechanistic basis for selecting soil amendments in remediation technologies.