Spherically granulated sodium ammonium ferrophosphatesilicate (FPS) of the empirical formula Na-0.32(NH4)(2.44)Fe6.17PSi8.9O30.9.14.3H(2)O has been synthesized using sol-gel technique. The FPS and its iron-substituted derivatives (FFPS) have been characterized by elemental analysis, X-ray diffraction, TGA, and porosity determination. Using the method of substitution of inner liquid the gels with high porosity and specific surface areas have been prepared. The opportunity of regulating the porosity has been shown. Changing the acidity of saturation by iron, gels with various content of iron hydroxide in inorganic polymer have been prepared. The exchange of arsenate anions on the iron-substituted form of FPS has been studied in batch condition. A high affinity towards arsenate anions in 0.05 M NaCl solutions has been shown. Arsenic uptake and degree of purification of solutions were found to depend on the amount of iron deposited in the gel framework. (C) 2004 Elsevier Ltd. All rights reserved.