現任中國土壤學會土壤化學專業委員會副主任、國際科學基金(IFS)科學顧問。先後訪問加拿大、澳大利亞、俄羅斯、印度、日本多國，開展表面化學、結構化學和土壤酸化等方面的合作研究，並與上述國家及美國、印度等國科學家建立了長期合作關係。長期從事可變電荷土壤的表面電化學性質、土壤酸度與酸化、土壤鋁化學和重金屬在土/水界面的化學行為的研究工作。近年來在低分子量有機酸在可變電荷土壤表面的吸附及其對土壤表面電化學性質的影響、有機酸對可變電荷土壤鋁化學行為的影響機制、可變電荷土壤中膠體顆粒表面雙電層的相互作用及其對養分和污染物界面化學行為影響、重金屬離子在土壤和Fe/Al氧化物表面的反應機制、酸化土壤的修復原理與技術等方面取得了創新性的研究成果，先後發表中、英文論文120餘篇，其中被SCI收錄68篇，在Soil Biology & Biochemistry, European Journal of Soil Science, Bioresource Technology, Geochimica et Cosmochimica Acta, Journal of Hazardous Materials, Geoderma和Chemosphere等國際頂級學術刊物上發表論文12篇，獲授權國家發明專利4項，主編中文專著1部，參與編寫中文專著3部、英文專著2部。2010年獲中國科學院朱李月華優秀教師獎。
Li, S.Z. and Xu, R.K. 2008. Electrical double layers’ interaction between oppositely charged particles as related to surface charge density and ionic strength. Colloids and Surfaces A: Physicochemical and Engineering Aspects 326:157-161.
2. Xu, R.K., Xiao S.C., Zhang, H., Jiang, J. and Ji, G.L. 2007. Adsorption of phthalic acid and salicylic acid by two variable charge soils as influenced by sulfate and phosphate. European Journal of Soil Science 58(1):335-342.
3. Li, J.Y., Xu, R.K., Tiwari, D. and Ji, G.L. 2006. Mechanism of aluminum release from variable charge soils induced by low-molecular-weight organic acids: kinetics study. Geochimica et Cosmochimica Acta 70: 2755-2764.
研究生獲獎情況
2005屆碩士畢業生李九玉獲中科院地奧獎學金二等獎，其畢業論文獲江蘇省2006年度優秀碩士論文；
2007屆碩士畢業生侯濤獲中國科學院院長獎學金優秀獎；
2008屆碩士畢業生李素珍的畢業論文獲江蘇省2009年度優秀碩士論文；
2011屆博士畢業生袁金華獲中國科學院院長獎學金優秀獎。
研究生論文代表作
(1) Li JY, Xu RK et al. 2006. Mechanism of aluminum release from variable charge soils induced by low-molecular-weight organic acids: kinetics study. Geochimica et Cosmochimica Acta70: 2755-2764. (2005屆碩士畢業生)
(2) Hou T, Xu RK et al. 2007. Interaction between electric double layers of soil colloids and Fe/Al oxides in suspensions. Journal of Colloid and Interface Science310: 670-674. (2007屆碩士畢業生)
(3) Liang J, Xu RK et al. 2007. Effect of arsenate on adsorption of Cd(II) by two variable charge soils. Chemosphere67(10): 1949-1955. (2007屆碩士畢業生)
(4) Li SZ, Xu RK et al. 2009. Electrical-double layer interaction between oppositely charged particles in variable charge soils as related to salt adsorption. Soil Science134(1): 27-34. (2008屆碩士畢業生)
(5) Li SZ and Xu RK. 2008. Electrical double layers’ interaction between oppositely charged particles as related to surface charge density and ionic strength. Colloids and Surfaces A: Physicochemical and Engineering Aspects326:157-161. (2008屆碩士畢業生)
(6) Wang Y, Xu RK et al. 2009. Phosphate adsorption at variable charge soils/water interfaces as influenced by ionic strength. Australian Journal of Soil Research47(5):529-536. (2008屆博士畢業生)
(7) Jiang J, Xu RK et al. 2008. The mechanism of chromate sorption by three variable charge soils. Chemosphere71(8): 1465-1471. (2009屆博士畢業生)
(8) Wang N, Xu RK et al. 2009. Use of various agricultural by-products to study the pH effects in an acid tea garden soil. Soil Use and Management25: 128-132. (2009屆碩士畢業生)
(9) Mao J, Xu RK et al. 2010. Effect of dicyandiamide on liming potential of two legume materials when incubated with an acid Ultisol. Soil Biology and Biochemistry42(9): 1632-1635 (2010屆碩士畢業生)
(10)Yuan JH, Xu RK and Zhang H. 2011. The forms of alkalis in the biochar produced from crop residues at different temperatures. Bioresource Technology102: 3488-3497. (2011屆博士畢業生)
(11)Yuan JH and Xu RK 2011. The amelioration effects of low temperature biochar generated from nine crop residues on an acidic Ultisol. Soil Use and Management27(1): 110-115. (2011屆博士畢業生)
(12)Wang YP, Xu RK and Li JY. 2011. Effect of Fe/Al oxides on desorption of Cd2+ from soils and minerals as related to diffuse layer overlapping. Soil Research49(3):231-237. (2011屆碩士畢業生)
