A new composite flocculant was synthesized by the copolymerization of acrylamide (AM), acryloyloxy-ethyltrimethyl ammonium chloride (DAC), and butylacrylate (BA) under ultraviolet (UV) radiation with 2,2'-azobis(2-methylpropionamide) dihydrochloride (V-50) as photo-initiator. This flocculant was named P(AM-DAC-BA). Nuclear magnetic resonance hydrogen spectroscopy (H-1 NMR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to observe the structure and morphology of P(AM-DAC-BA). Parameters affecting the intrinsic viscosity ([eta]) and conversion of P(AM-DAC-BA), such as monomer concentration, photo-initiator concentration, pH, illumination time, and incident light intensity in a quartz or glass reactor were examined. Results showed that the optimum conditions were 30 wt% total monomers, 2.0 wt% hydrophobic monomer, 0.5 wt parts per thousand photo-initiator, pH 4.4, 100 min of illumination time, and 1160 mu M cm(-2) incident light intensity. To study the dewatering performance of P(AM-DAC-BA), the textile sewage sludge dewatering was evaluated by measuring both the residual turbidity and moisture content of the filter cake. At 50 mg L-1 P(AM-DAC-BA) and pH 11.6, the residual turbidity of the supernatant and moisture content of the dewatered filter cake reached 5.5 NTU and 73.2%, respectively. Dewatering tests demonstrated the superiority of P(AM-DAC-BA) flocculant synthesized in the quartz reactor over that synthesized in the glass reactor. (C) 2013 Elsevier B.V. All rights reserved.