土壤胶体化学和表面反应.pptx

第八章 土壤胶体化学和表面反应 Soil Colloidal Chemistry and Surface Reaction 8.1 Surface properties of soil colloid 土壤胶体的表面性质 8.2 Adsorption and exchange of cations by soil colloids 土壤胶体对阳离子的吸附交换反应 8.3 Adsorption and exchange of anions by soil colloids 土壤胶体对阴离子的吸附与交换 ; Concepts of soil colloid The colloid is a state of matter consisting of very fine particles that approach but never reach molecular sizes. (0.2μm~5nm) Soils contain large amounts of soil material in a colloidal state. Clay comprises all inorganic solids smaller than 0.002mm (2μm) in effective diameter and is considered a colloid. Soil organic matter and plant solids also occur in the colloidal state.;一、土壤胶体表面类型 Surface category of soil colloid 土壤胶体: 无机胶体(粘粒)和有机胶体(腐殖质),多呈有机—无机复合胶体。 ; 按表面的化学结构特点可分为: 硅氧烷型、水合氧化物型和有机物表面 硅氧烷型表面 Siloxane surface Si—O—Si Siloxane surface is characterized by surface planes of oxygen atoms, underlaid by silican atoms of tetrahedrons. The charge is mainly attributed to isomorphous substitution of the underlaying silicon atoms of the tetrahedrons. 2:1型粘粒的上、下两面，1:1型粘粒1/2面。 非极性的疏水表面。 电荷来源为同晶置换(Al3+→Si4+)，少部分是边角断键，为永久电荷。 ; 硅氧烷型表面 Siloxane surface Si Si O; 水合氧化物型表面 Oxy-hydroxide surface 由金属阳离子和氢氧基组成的表面 M－OH Surface is characterized by planes of exposed hydroxyl, OH, groups, underlaid by Al, Fe or Si atoms in the center of the octahedrons. The exposed hydroxylgroups are subject to dissociation and play an important role in the development of negative charge. 铝醇Al—OH，铁醇Fe—OH，硅烷醇Si—OH等。水铝(镁)片，铁、铝氧化物及硅片边角断键。 极性亲水表面。 电荷来源为表面—OH基质子的缔合—OH2+ 或 离解—OH→—O- + H+。可变电荷。 ; 水合氧化物型表面 Oxy-hydroxide surface M—OH; 有机物表面 Organic material surface 腐殖物质为主的表面，表面羧基(—COOH)、酚羟基(—OH)、氨基(—NH2)等活性基团。离解H+或缔合H+产生表面电荷。 R—COOH·H2O R—COO-+H3O+ R—NH2·H2O R—NH3++OH- 电荷